[RBW] Re: Shimmy, according to BQ
Doug I am arriving at that conclusion and towards that end I'm also prepared to rule out one compelling variable. My experiments suggest that the compliance (flexibility) of the rear rack itself is NOT a significant contributor to shimmy on my Hillborne. The experiment was that I swapped rear racks between the Hillborne and the Bombadil. The Nitto R-14 was the original Hillborne rack and we speculated whether that minimalist rack could be flexing at a resonant frequency that matched the front end of the bike and resulted in shimmy. My Burley brand cromoly rack is WAY stiffer, and with a similar load, the Hillborne shimmies exactly like it did with the R-14. In a related experiment, the Bombadil shimmies with a similar load on it, also with both racks. The shimmy on the Bombadil differs in frequency(higher) and amplitude(smaller), but it does it. That's excellent progress, I think. Next step I'll try to fix a shimmy state by adding weight in the front and leaving the weight in the back constant. On Dec 22 2010, 6:54 pm, doug peterson dougpn...@cox.net wrote: I've run similar loading experiments on my Atlantis. The unloaded set- up is a Nitto small front rack with Acorn Box Rando bag which I often load up to 6-8 lbs without issue. I have a Nitto Big Rear Rack (2 lbs of real steel) for anything I may pick up along the way. Unless I've got a box of books or similar casually strapped to the back, the bike is stable although the steering feels a bit wandering if I need to take both hands off the bars. Not a big deal. The Atlantis willshimmywith extra weight only on the rear (2 panniers, total weight less than 20 lbs), such as a lodging tour load. Move that same load to front low riders, noshimmy. Add another pair of panniers for camping (15 lbs total), and the most stable arrangement is with the lighter pair on the rear. 4 bags, with the heavier on the rear, and the bike has that tail wagging the dog feel, and has developed a nastyshimmymore than once. The above is all with the same 35 mm touring tires and a 175 lb rider. I've fiddled with the headset adjustment, etc., and will change to a needle bearing HS when the present one dies. My conclusion, for me what I do with the bike, is to put the bulk of any load on the front, with whatever's left over on the rear. William may have reached the same conlusion in his post where he reports eliminating theshimmywhen he removed the rear saddlebag (12 lbs). In any case, these experiments are great fun to perform and we learn a lot about our bikes, preferences, and what works for us. Rene (above) is the only other Atlantis owner I can recall posting aboutshimmy. dougP On Dec 22, 11:09 am, William tapebu...@gmail.com wrote: The drinard video is very good. That's exactly the thing I'm looking at when running my experiments. On Dec 21, 9:34 pm, Tim McNamara tim...@bitstream.net wrote: Try the simple things first: move the saddle slightly forward or back, maybe 1/2, to change the weight distribution of you on the bike. Change the distribution of stuff you carry on the bike (or consider carrying less stuff). Raise or lower the bars to change your position. Make sure the headset is adjusted. Make sure the wheels are true and properly aligned in the frame. Swap the front tire to the back and vice versa; look for casing defects in the tires. Try less inflation pressure (or more) in the tires. Try a different size tire. If your bike starts toshimmywith your hands on the bars, stand up slightly and ease your weight off the saddle- this will usually stop ashimmyinstantly. The cause ofshimmyis not exactly known. Since it tends to be speed- dependent, it is likely that vertical and gyroscopic forces play a part. There appear to be at least two fulcrum points, the rear tire contact patch and the saddle. The bike frame appears to act as a spring, whipping back and forth; nutation can be observed with the steerer turning slightly in the head bearings as the front part of the frame travels laterally. Interestingly the front tire contact patch usually continues to track in a straight line but, as the shimmyworsens, the contact patch can begin to arc back and forth on the road. This is what is often meant when someone talks about a death wobble, because the vehicle becomes unstable and will often crash unless the wobble can be stopped. Wobbles can be started by road surface irregularities *Great* video by the much-missed-in-rec.bikes.tech Damon Rinard of a deliberately induced no-handedshimmy: http://www.youtube.com/watch?v=xODNzyUbIHo I wish that was in slo-mo. This is Rob English crashing at the Battle Mountain IHPVA event on level terrain at about 70 mph (I bet he appreciated his fairing very much). It appears to me that his pedaling effort caused the problem and
[RBW] Re: Shimmy, according to BQ
Tim wrote: This is Rob English crashing at the Battle Mountain IHPVA event on level terrain at about 70 mph (I bet he appreciated his fairing very much). It appears to me that his pedaling effort caused the problem and that as the bike started to wobble, his pedaling amplified it. Totally non-Riv content, but it's a small world of awesome - that's the same Rob English who built my favorite 18.5 lb steel 29er at the Oregon Handbuilt Bicycle Show: http://www.biketinker.com/2010/fine-bikes/english-cycles-mountain-bike/ And this 11.5 pound steel road bike: http://www.flickr.com/photos/philipwilliamson/5067220826/ Coincidentally, a related Youtube video shows Rob explaining how to stop shimmy on a Bike Friday... all the same things just mentioned, but no magic hammer. Philip Philip Williamson www.biketinker.com -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
The drinard video is very good. That's exactly the thing I'm looking at when running my experiments. On Dec 21, 9:34 pm, Tim McNamara tim...@bitstream.net wrote: Try the simple things first: move the saddle slightly forward or back, maybe 1/2, to change the weight distribution of you on the bike. Change the distribution of stuff you carry on the bike (or consider carrying less stuff). Raise or lower the bars to change your position. Make sure the headset is adjusted. Make sure the wheels are true and properly aligned in the frame. Swap the front tire to the back and vice versa; look for casing defects in the tires. Try less inflation pressure (or more) in the tires. Try a different size tire. If your bike starts to shimmy with your hands on the bars, stand up slightly and ease your weight off the saddle- this will usually stop a shimmy instantly. The cause of shimmy is not exactly known. Since it tends to be speed- dependent, it is likely that vertical and gyroscopic forces play a part. There appear to be at least two fulcrum points, the rear tire contact patch and the saddle. The bike frame appears to act as a spring, whipping back and forth; nutation can be observed with the steerer turning slightly in the head bearings as the front part of the frame travels laterally. Interestingly the front tire contact patch usually continues to track in a straight line but, as the shimmy worsens, the contact patch can begin to arc back and forth on the road. This is what is often meant when someone talks about a death wobble, because the vehicle becomes unstable and will often crash unless the wobble can be stopped. Wobbles can be started by road surface irregularities *Great* video by the much-missed-in-rec.bikes.tech Damon Rinard of a deliberately induced no-handed shimmy: http://www.youtube.com/watch?v=xODNzyUbIHo I wish that was in slo-mo. This is Rob English crashing at the Battle Mountain IHPVA event on level terrain at about 70 mph (I bet he appreciated his fairing very much). It appears to me that his pedaling effort caused the problem and that as the bike started to wobble, his pedaling amplified it. http://www.youtube.com/watch?v=i5Dapy1xUq0 My observations with my bikes (a 1996 Riv A/R [26 x 1.25], a 1995 Ritchey Road custom [700 x 25], a 1998 Gunnar Crosshairs [700 x 28] and a home-built road bike [700 x 25] all with Panaracer Pasela tires at the rated maximum pressure) is that: 1. none of them currently shimmy with my hands on the bars. 2. the Gunnar shimmied when I mounted a Nitto mini-rack on the front fork, even with no load on the rack, and stopped as soon as I removed the rack- I could feel the pulsation in my hands when they were on the bars. The Gunnar sometimes shimmies if I ride no handed and lean back. Reynolds 853 with Waterford fork upgrade. Oddly it did not shimmy with a really old Eclipse bar bag (one of the ones from the late 70s with a rack that slipped over the bars and under the stem and with elastic cords going down to the dropouts). 3. the Riv doesn't, with or without the same Nitto mini rack, with or without a load. Reynolds 753 frame with 531 fork. No shimmy that I can ever recall having on this bike. 4. the Ritchey shimmies at certain speeds no-handed (19-20 mph and up) if coasting but not if pedaling; worse if I lean back. Tange Prestige Ritchey Logic tubes and fork tubes. 5. the home built bike shimmies occasionally no-handed. Reynolds 501 frame and fork tubes. 5. the scariest shimmy I ever had was descending on a Bianchi Reparto Corsa-built bike when I tried the aero trick of sliding off the back of the saddle. It felt like the rear wheel was shimmying, very disconcerting. The Ritchey replaced that bike and handles so much better than the Italian job. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I've run similar loading experiments on my Atlantis. The unloaded set- up is a Nitto small front rack with Acorn Box Rando bag which I often load up to 6-8 lbs without issue. I have a Nitto Big Rear Rack (2 lbs of real steel) for anything I may pick up along the way. Unless I've got a box of books or similar casually strapped to the back, the bike is stable although the steering feels a bit wandering if I need to take both hands off the bars. Not a big deal. The Atlantis will shimmy with extra weight only on the rear (2 panniers, total weight less than 20 lbs), such as a lodging tour load. Move that same load to front low riders, no shimmy. Add another pair of panniers for camping (15 lbs total), and the most stable arrangement is with the lighter pair on the rear. 4 bags, with the heavier on the rear, and the bike has that tail wagging the dog feel, and has developed a nasty shimmy more than once. The above is all with the same 35 mm touring tires and a 175 lb rider. I've fiddled with the headset adjustment, etc., and will change to a needle bearing HS when the present one dies. My conclusion, for me what I do with the bike, is to put the bulk of any load on the front, with whatever's left over on the rear. William may have reached the same conlusion in his post where he reports eliminating the shimmy when he removed the rear saddlebag (12 lbs). In any case, these experiments are great fun to perform and we learn a lot about our bikes, preferences, and what works for us. Rene (above) is the only other Atlantis owner I can recall posting about shimmy. dougP On Dec 22, 11:09 am, William tapebu...@gmail.com wrote: The drinard video is very good. That's exactly the thing I'm looking at when running my experiments. On Dec 21, 9:34 pm, Tim McNamara tim...@bitstream.net wrote: Try the simple things first: move the saddle slightly forward or back, maybe 1/2, to change the weight distribution of you on the bike. Change the distribution of stuff you carry on the bike (or consider carrying less stuff). Raise or lower the bars to change your position. Make sure the headset is adjusted. Make sure the wheels are true and properly aligned in the frame. Swap the front tire to the back and vice versa; look for casing defects in the tires. Try less inflation pressure (or more) in the tires. Try a different size tire. If your bike starts to shimmy with your hands on the bars, stand up slightly and ease your weight off the saddle- this will usually stop a shimmy instantly. The cause of shimmy is not exactly known. Since it tends to be speed- dependent, it is likely that vertical and gyroscopic forces play a part. There appear to be at least two fulcrum points, the rear tire contact patch and the saddle. The bike frame appears to act as a spring, whipping back and forth; nutation can be observed with the steerer turning slightly in the head bearings as the front part of the frame travels laterally. Interestingly the front tire contact patch usually continues to track in a straight line but, as the shimmy worsens, the contact patch can begin to arc back and forth on the road. This is what is often meant when someone talks about a death wobble, because the vehicle becomes unstable and will often crash unless the wobble can be stopped. Wobbles can be started by road surface irregularities *Great* video by the much-missed-in-rec.bikes.tech Damon Rinard of a deliberately induced no-handed shimmy: http://www.youtube.com/watch?v=xODNzyUbIHo I wish that was in slo-mo. This is Rob English crashing at the Battle Mountain IHPVA event on level terrain at about 70 mph (I bet he appreciated his fairing very much). It appears to me that his pedaling effort caused the problem and that as the bike started to wobble, his pedaling amplified it. http://www.youtube.com/watch?v=i5Dapy1xUq0 My observations with my bikes (a 1996 Riv A/R [26 x 1.25], a 1995 Ritchey Road custom [700 x 25], a 1998 Gunnar Crosshairs [700 x 28] and a home-built road bike [700 x 25] all with Panaracer Pasela tires at the rated maximum pressure) is that: 1. none of them currently shimmy with my hands on the bars. 2. the Gunnar shimmied when I mounted a Nitto mini-rack on the front fork, even with no load on the rack, and stopped as soon as I removed the rack- I could feel the pulsation in my hands when they were on the bars. The Gunnar sometimes shimmies if I ride no handed and lean back. Reynolds 853 with Waterford fork upgrade. Oddly it did not shimmy with a really old Eclipse bar bag (one of the ones from the late 70s with a rack that slipped over the bars and under the stem and with elastic cords going down to the dropouts). 3. the Riv doesn't, with or without the same Nitto mini rack, with or without a load. Reynolds 753 frame with 531 fork. No
[RBW] Re: Shimmy, according to BQ
William: Did you note the weights at each end? Riv says the R-14 isn't meant for much weight (don't recall the number but it's conservative) so perhaps some rack movement? dougP On Dec 21, 1:25 pm, William tapebu...@gmail.com wrote: Update on the research front. In the next round of testing I put the identical load on a different bike. I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. On Dec 20, 10:59 am, William tapebu...@gmail.com wrote: Yeah, I've read that article. What light were you referring to? In that article he definitely makes himself look smart by describing 'nutation' which is a term that 99.9% of his readers don't know. He describes that as a driving force for why bikes shimmy, but has only guesses for why bikes don't shimmy. He says the bikes he built don't shimmy, and after the fact guesses why they don't. He also has specified and implied things to try if your bike does shimmy, but just like anyone else, he can't specify a combination of things that will yield shimmy. As a group, these experts all seem to regard shimmy the way any of us would. It's an unpleasant attribute of a bike that you'd just like to have go away, so you can resume enjoying yourself on your bike. Just change stuff and expect that eventually you'll find a configuration that behaves more like you want. If you find such a configuration, be happy and ride. If it comes up again, repeat the process. The experts with whom you consult might have their own pet remedy to try first, and take it for what it's worth, an educated guess. For my experiments, I've moved to loading my Bombadil with bullmoose bars with the identical load that the shimmy-Hillborne had. Nitto Mini and small trunksack in front. Nitto R-14 and Saddlesack Large in back. I'll ride that around (weather permitting) and see what comes of that. On Dec 17, 3:34 pm, Bill webe...@gmail.com wrote: Builder Dave Moulton sheds some light on the subject in this 2006 blog entry: http://davesbikeblog.squarespace.com/blog/2006/8/18/shimmy-re-visited... On Dec 13, 7:59 pm, William tapebu...@gmail.com wrote: I weigh about 175. The whole bike rig with both bags on it as described above is probably in the low 40s. So maybe 215 bike + cargo + rider. Straight medium. :) My bars are 1-2 inches above saddle height. On Dec 13, 4:21 pm, Seth Vidal skvi...@gmail.com wrote: On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
On Tue, Dec 21, 2010 at 13:25, William tapebu...@gmail.com wrote: I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. The R-14 looks to my eye like it would be very flexible. I still think that it is the main culprit here. It would be an interesting experiment to keep everything the same but have the bag on a stiffer rack. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I'm tracking that...In my notes I estimated the Sackville Saddlesack Large and it's contents weighed 12 pounds. There are numerous speculations in the literature about high mounted floppy loads being associated with shimmy. Nobody conclusively says that such things are causes or enablers of shimmy, or will bet their life on removing such loads being a cure to shimmy. Another near-term experiment will be to load the same Saddlesack large to a much stiffer rear rack. The Hillborne now has the rack that came with my Burley Piccolo. It's a beast. Fat cro-mo tubes welded, bomber. If the shimmy comes from rear load floppiness, and if the critical flopiness comes from the rack, then that Burley rack should change the shimmy properties substantially. If the critical flopiness comes from the Saddlesack large, then the rack won't change anything. On Dec 21, 2:15 pm, doug peterson dougpn...@cox.net wrote: William: Did you note the weights at each end? Riv says the R-14 isn't meant for much weight (don't recall the number but it's conservative) so perhaps some rack movement? dougP On Dec 21, 1:25 pm, William tapebu...@gmail.com wrote: Update on the research front. In the next round of testing I put the identical load on a different bike. I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. On Dec 20, 10:59 am, William tapebu...@gmail.com wrote: Yeah, I've read that article. What light were you referring to? In that article he definitely makes himself look smart by describing 'nutation' which is a term that 99.9% of his readers don't know. He describes that as a driving force for why bikes shimmy, but has only guesses for why bikes don't shimmy. He says the bikes he built don't shimmy, and after the fact guesses why they don't. He also has specified and implied things to try if your bike does shimmy, but just like anyone else, he can't specify a combination of things that will yield shimmy. As a group, these experts all seem to regard shimmy the way any of us would. It's an unpleasant attribute of a bike that you'd just like to have go away, so you can resume enjoying yourself on your bike. Just change stuff and expect that eventually you'll find a configuration that behaves more like you want. If you find such a configuration, be happy and ride. If it comes up again, repeat the process. The experts with whom you consult might have their own pet remedy to try first, and take it for what it's worth, an educated guess. For my experiments, I've moved to loading my Bombadil with bullmoose bars with the identical load that the shimmy-Hillborne had. Nitto Mini and small trunksack in front. Nitto R-14 and Saddlesack Large in back. I'll ride that around (weather permitting) and see what comes of that. On Dec 17, 3:34 pm, Bill webe...@gmail.com wrote: Builder Dave Moulton sheds some light on the subject in this 2006 blog entry: http://davesbikeblog.squarespace.com/blog/2006/8/18/shimmy-re-visited... On Dec 13, 7:59 pm, William tapebu...@gmail.com wrote: I weigh about 175. The whole bike rig with both bags on it as described above is probably in the low 40s. So maybe 215 bike + cargo + rider. Straight medium. :) My bars are 1-2 inches above saddle height. On Dec 13, 4:21 pm, Seth Vidal skvi...@gmail.com wrote: On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
On Tue, 2010-12-21 at 14:29 -0800, William wrote: Nobody conclusively says that such things are causes or enablers of shimmy, or will bet their life on removing such loads being a cure to shimmy They'd be very foolish to do so, since there are many things that can cause shimmy including rider behavior. Another near-term experiment will be to load the same Saddlesack large to a much stiffer rear rack. The Hillborne now has the rack that came with my Burley Piccolo. It's a beast. Fat cro-mo tubes welded, bomber. If the shimmy comes from rear load floppiness, and if the critical flopiness comes from the rack, then that Burley rack should change the shimmy properties substantially. If the critical flopiness comes from the Saddlesack large, then the rack won't change anything. I hope you solve your problem, but when you've done it you still won't be able to make any kind of sweeping, definitive statement about what causes and what cures shimmy. At most you'll be able to say I did this to cure mine. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I was thinking another variable may be wheels. Have you tried swapping wheels from another bike to see if that changes or helps anything? Or tire switching as well? both seem like easy changes to make. Rotating components can certainly affect the dynamic response of the bike. Other things like frame alignment, new headsets and such are more costly to do. Keep trying.. ~Mike~ On Dec 21, 2:37 pm, Steve Palincsar palin...@his.com wrote: On Tue, 2010-12-21 at 14:29 -0800, William wrote: Nobody conclusively says that such things are causes or enablers of shimmy, or will bet their life on removing such loads being a cure to shimmy They'd be very foolish to do so, since there are many things that can cause shimmy including rider behavior. Another near-term experiment will be to load the same Saddlesack large to a much stiffer rear rack. The Hillborne now has the rack that came with my Burley Piccolo. It's a beast. Fat cro-mo tubes welded, bomber. If the shimmy comes from rear load floppiness, and if the critical flopiness comes from the rack, then that Burley rack should change the shimmy properties substantially. If the critical flopiness comes from the Saddlesack large, then the rack won't change anything. I hope you solve your problem, but when you've done it you still won't be able to make any kind of sweeping, definitive statement about what causes and what cures shimmy. At most you'll be able to say I did this to cure mine. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I understand it well enough on my Hillborne that I can avoid shimmy when I want to, so I don't think I have a problem to solve. We've never read a convincing description for why bikes shimmy, that's true. But I'd argue we've never read a convincing description for why any INDIVIDUAL bike shimmies. At least I want to get to that point. The thing I'm doing that I think differs from the 'experts' is that I'm deliberately making it happen to see if I can develop a more general understanding. The thing I've not seen in any of the commonly cited articles (Heine, Brandt, Moulton, Sheldon(RIP)) is that in none of them has the author deliberately made shimmy happen in order to study it. They all report their own experiences and second hand rumors of poking around trying to fix it on somebody's bike (only sometimes their own) and guessing at what the causes were and what worked after the fact. My hypothesis is that it's a tuned resonance problem. When multiple structures have matching resonant properties they get to ringing at max amplitude. If that's what you have, changing the resonant frequency of one, so that it doesn't match the other will make the ringing subside. The Taipei 101 skyscraper has a relatively tiny pendulum near its roof to cancel out resonance of the building from earthquakes. Several, maybe all the authors above would agree it's a tuned resonance problem, but they don't agree on what the resonating subsystems are. If you don't know what they are, you certainly can't deliberately and precisely tune or de-tune them. Jan suspects that the top tube and the down tube are separate resonators, and that bikes that have the same diameter tubing in the top tube and the downtube are tuned to each other and are much more likely to shimmy. Moulton guesses that the chainstays are in some way a semi-isolated subsystem and his use of Columbus SP tubing in chainstays gave his bikes anti- shimmy properties. Others say that frame flex has nothing to do with any of this. On Dec 21, 2:37 pm, Steve Palincsar palin...@his.com wrote: On Tue, 2010-12-21 at 14:29 -0800, William wrote: Nobody conclusively says that such things are causes or enablers of shimmy, or will bet their life on removing such loads being a cure to shimmy They'd be very foolish to do so, since there are many things that can cause shimmy including rider behavior. Another near-term experiment will be to load the same Saddlesack large to a much stiffer rear rack. The Hillborne now has the rack that came with my Burley Piccolo. It's a beast. Fat cro-mo tubes welded, bomber. If the shimmy comes from rear load floppiness, and if the critical flopiness comes from the rack, then that Burley rack should change the shimmy properties substantially. If the critical flopiness comes from the Saddlesack large, then the rack won't change anything. I hope you solve your problem, but when you've done it you still won't be able to make any kind of sweeping, definitive statement about what causes and what cures shimmy. At most you'll be able to say I did this to cure mine. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Just looked up the R-14 on Riv's site: 13 lbs capacity. It's surprising how quickly weight can add up. The R-14 is an elegant looking rack but with just the support struts for stability it may lack lateral stiffness. dougP On Dec 21, 2:20 pm, james black chocot...@gmail.com wrote: On Tue, Dec 21, 2010 at 13:25, William tapebu...@gmail.com wrote: I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. The R-14 looks to my eye like it would be very flexible. I still think that it is the main culprit here. It would be an interesting experiment to keep everything the same but have the bag on a stiffer rack. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
I've got a 56 Sam that I ran a R-14 on with 2 Ortliebs fairly well loaded, or (alternatively) a Big Loafer on top... nary a shimmy (with a mini+loaf on the front). ymmv, of course, but i never noticed any flexiness from the R-14. -a On Dec 21, 2010, at 8:08 PM, doug peterson wrote: Just looked up the R-14 on Riv's site: 13 lbs capacity. It's surprising how quickly weight can add up. The R-14 is an elegant looking rack but with just the support struts for stability it may lack lateral stiffness. dougP On Dec 21, 2:20 pm, james black chocot...@gmail.com wrote: On Tue, Dec 21, 2010 at 13:25, William tapebu...@gmail.com wrote: I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. The R-14 looks to my eye like it would be very flexible. I still think that it is the main culprit here. It would be an interesting experiment to keep everything the same but have the bag on a stiffer rack. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
whups, scratch that - i've used the R-FIFTEEN, not the R-14. -a On Dec 21, 8:14 pm, andrew hill neurod...@gmail.com wrote: I've got a 56 Sam that I ran a R-14 on with 2 Ortliebs fairly well loaded, or (alternatively) a Big Loafer on top... nary a shimmy (with a mini+loaf on the front). ymmv, of course, but i never noticed any flexiness from the R-14. -a On Dec 21, 2010, at 8:08 PM, doug peterson wrote: Just looked up the R-14 on Riv's site: 13 lbs capacity. It's surprising how quickly weight can add up. The R-14 is an elegant looking rack but with just the support struts for stability it may lack lateral stiffness. dougP On Dec 21, 2:20 pm, james black chocot...@gmail.com wrote: On Tue, Dec 21, 2010 at 13:25, William tapebu...@gmail.com wrote: I loaded my 56cm Bombadil with the trunksack small on the Nitto Mini front. I moved the Nitto R-14 rear and the loaded Saddlesack Large over to the Bombadil. The Bombadil does shimmy with that load. But it is at a much higher frequency and a smaller amplitude. The amplitude was almost small enough to just ignore. It also happened at a somewhat higher speed. More notes for the notebook. The R-14 looks to my eye like it would be very flexible. I still think that it is the main culprit here. It would be an interesting experiment to keep everything the same but have the bag on a stiffer rack. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group athttp://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
I was thinking that the factor is the weight of the rear bag, not the rack. Can you verify if without the rack but with the bag anything changes? My Atlantis with the same rack-bag combo + Noodle bars and shimmies. When I put the Albatross bars it didn't shimmy but I couldn't get used to them. Now I'm putting the Noodles back on and will see what happens. Running 50mm Marathon Supremes. Rene Sent from my iPhone 4 On Dec 21, 2010, at 3:27 PM, Michael_S mikeybi...@rocketmail.com wrote: I was thinking another variable may be wheels. Have you tried swapping wheels from another bike to see if that changes or helps anything? Or tire switching as well? both seem like easy changes to make. Rotating components can certainly affect the dynamic response of the bike. Other things like frame alignment, new headsets and such are more costly to do. Keep trying.. ~Mike~ On Dec 21, 2:37 pm, Steve Palincsar palin...@his.com wrote: On Tue, 2010-12-21 at 14:29 -0800, William wrote: Nobody conclusively says that such things are causes or enablers of shimmy, or will bet their life on removing such loads being a cure to shimmy They'd be very foolish to do so, since there are many things that can cause shimmy including rider behavior. Another near-term experiment will be to load the same Saddlesack large to a much stiffer rear rack. The Hillborne now has the rack that came with my Burley Piccolo. It's a beast. Fat cro-mo tubes welded, bomber. If the shimmy comes from rear load floppiness, and if the critical flopiness comes from the rack, then that Burley rack should change the shimmy properties substantially. If the critical flopiness comes from the Saddlesack large, then the rack won't change anything. I hope you solve your problem, but when you've done it you still won't be able to make any kind of sweeping, definitive statement about what causes and what cures shimmy. At most you'll be able to say I did this to cure mine. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Try the simple things first: move the saddle slightly forward or back, maybe 1/2, to change the weight distribution of you on the bike. Change the distribution of stuff you carry on the bike (or consider carrying less stuff). Raise or lower the bars to change your position. Make sure the headset is adjusted. Make sure the wheels are true and properly aligned in the frame. Swap the front tire to the back and vice versa; look for casing defects in the tires. Try less inflation pressure (or more) in the tires. Try a different size tire. If your bike starts to shimmy with your hands on the bars, stand up slightly and ease your weight off the saddle- this will usually stop a shimmy instantly. The cause of shimmy is not exactly known. Since it tends to be speed- dependent, it is likely that vertical and gyroscopic forces play a part. There appear to be at least two fulcrum points, the rear tire contact patch and the saddle. The bike frame appears to act as a spring, whipping back and forth; nutation can be observed with the steerer turning slightly in the head bearings as the front part of the frame travels laterally. Interestingly the front tire contact patch usually continues to track in a straight line but, as the shimmy worsens, the contact patch can begin to arc back and forth on the road. This is what is often meant when someone talks about a death wobble, because the vehicle becomes unstable and will often crash unless the wobble can be stopped. Wobbles can be started by road surface irregularities *Great* video by the much-missed-in-rec.bikes.tech Damon Rinard of a deliberately induced no-handed shimmy: http://www.youtube.com/watch?v=xODNzyUbIHo I wish that was in slo-mo. This is Rob English crashing at the Battle Mountain IHPVA event on level terrain at about 70 mph (I bet he appreciated his fairing very much). It appears to me that his pedaling effort caused the problem and that as the bike started to wobble, his pedaling amplified it. http://www.youtube.com/watch?v=i5Dapy1xUq0 My observations with my bikes (a 1996 Riv A/R [26 x 1.25], a 1995 Ritchey Road custom [700 x 25], a 1998 Gunnar Crosshairs [700 x 28] and a home-built road bike [700 x 25] all with Panaracer Pasela tires at the rated maximum pressure) is that: 1. none of them currently shimmy with my hands on the bars. 2. the Gunnar shimmied when I mounted a Nitto mini-rack on the front fork, even with no load on the rack, and stopped as soon as I removed the rack- I could feel the pulsation in my hands when they were on the bars. The Gunnar sometimes shimmies if I ride no handed and lean back. Reynolds 853 with Waterford fork upgrade. Oddly it did not shimmy with a really old Eclipse bar bag (one of the ones from the late 70s with a rack that slipped over the bars and under the stem and with elastic cords going down to the dropouts). 3. the Riv doesn't, with or without the same Nitto mini rack, with or without a load. Reynolds 753 frame with 531 fork. No shimmy that I can ever recall having on this bike. 4. the Ritchey shimmies at certain speeds no-handed (19-20 mph and up) if coasting but not if pedaling; worse if I lean back. Tange Prestige Ritchey Logic tubes and fork tubes. 5. the home built bike shimmies occasionally no-handed. Reynolds 501 frame and fork tubes. 5. the scariest shimmy I ever had was descending on a Bianchi Reparto Corsa-built bike when I tried the aero trick of sliding off the back of the saddle. It felt like the rear wheel was shimmying, very disconcerting. The Ritchey replaced that bike and handles so much better than the Italian job. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Builder Dave Moulton sheds some light on the subject in this 2006 blog entry: http://davesbikeblog.squarespace.com/blog/2006/8/18/shimmy-re-visited.html On Dec 13, 7:59 pm, William tapebu...@gmail.com wrote: I weigh about 175. The whole bike rig with both bags on it as described above is probably in the low 40s. So maybe 215 bike + cargo + rider. Straight medium. :) My bars are 1-2 inches above saddle height. On Dec 13, 4:21 pm, Seth Vidal skvi...@gmail.com wrote: On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Yeah, I've read that article. What light were you referring to? In that article he definitely makes himself look smart by describing 'nutation' which is a term that 99.9% of his readers don't know. He describes that as a driving force for why bikes shimmy, but has only guesses for why bikes don't shimmy. He says the bikes he built don't shimmy, and after the fact guesses why they don't. He also has specified and implied things to try if your bike does shimmy, but just like anyone else, he can't specify a combination of things that will yield shimmy. As a group, these experts all seem to regard shimmy the way any of us would. It's an unpleasant attribute of a bike that you'd just like to have go away, so you can resume enjoying yourself on your bike. Just change stuff and expect that eventually you'll find a configuration that behaves more like you want. If you find such a configuration, be happy and ride. If it comes up again, repeat the process. The experts with whom you consult might have their own pet remedy to try first, and take it for what it's worth, an educated guess. For my experiments, I've moved to loading my Bombadil with bullmoose bars with the identical load that the shimmy-Hillborne had. Nitto Mini and small trunksack in front. Nitto R-14 and Saddlesack Large in back. I'll ride that around (weather permitting) and see what comes of that. On Dec 17, 3:34 pm, Bill webe...@gmail.com wrote: Builder Dave Moulton sheds some light on the subject in this 2006 blog entry: http://davesbikeblog.squarespace.com/blog/2006/8/18/shimmy-re-visited... On Dec 13, 7:59 pm, William tapebu...@gmail.com wrote: I weigh about 175. The whole bike rig with both bags on it as described above is probably in the low 40s. So maybe 215 bike + cargo + rider. Straight medium. :) My bars are 1-2 inches above saddle height. On Dec 13, 4:21 pm, Seth Vidal skvi...@gmail.com wrote: On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ NRC
I did in fact, mean 26 frame w/ 27 wheels. Sent from my Verizon Wireless BlackBerry -Original Message- From: Bill M. bmenn...@comcast.net Sender: rbw-owners-bunch@googlegroups.com Date: Sun, 12 Dec 2010 22:22:52 To: RBW Owners Bunchrbw-owners-bunch@googlegroups.com Reply-To: rbw-owners-bunch@googlegroups.com Subject: [RBW] Re: Shimmy, according to BQ NRC You sure he didn't mean a 26 frame size (not wheel size)? On Dec 12, 11:42 am, Steve Palincsar palin...@his.com wrote: On Sun, 2010-12-12 at 14:40 -0500, Robert Zeidler wrote: I concur with your opinion on the Paramount. I, too, have a few of the 26 bikes, all 531 , and find they are rock steady. Is this a 27 wheel thing maybe? I do not recall a 1972 Paramount coming with 26 wheels. FWIW, mine had 27. The other option was tubulars. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Hey, I resemble that remark. 220 also. More a combination of not having more major hills to descend and being a natural born chicken. But, hey, we need the eggs. Actually those photos aren't scary to me. In fact, would be nice to have only that much snow on the ground. Could have been out riding this weekend. We received 17 inches in the latest storm. Side roads are still unplowed or at best two cars wide. With very compacted snow. For me, that's scary. Eric Platt St. Paul, MN On Dec 12, 10:06 pm, Kelly tkslee...@gmail.com wrote: Well being 220 lbs means gravity is my friend on the downhill. That 57 was scary with the wobble but have hit 65 mph on long straight shot that was solid smooth and not scary at all. The desire to go that fast has finally faded. I guess the adrenalin junky in me has settled down.. another good reason to sell the race bike and get the ahh.. :) But then the ride to starbucks and walgreens today was just as scary as that speed :)http://www.flickr.com/photos/tksleeper/sets/72157625582548862/ Kelly -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I've run my first several experiments. My bike was in a state where it was really easy to make it shimmy in a way that was/is not life threatening. The bike is a 56cm Hillborne. It's got fenders, front and rear racks a Saddlesack Large on the back and a Trunksack small in front. Riding no hands on smooth flat road it shimmies about 3/4 amplitude at the stem bolt at about 4Hz. Putting a knee on the top tube stops it. I wanted to start with things that I can change for free on the bike and see how that affects shimmy. Test 1: Pump up front tire (Jack Brown blue) from 30psi to 70psi. Result--no change. Still shimmies at will Test 2: Pump up rear tire (JB blue) from 30psi to 70psi. Result--no change. Still shimmies exactly the same Test 3: Remove Trunksack and contents from front of bike (3-4lbs of weight). Result--no change. Still shimmies easily, same amplitude, same frequency as far as I can tell Test 4: Remove Saddlesack Large and contents from the back (10-12lbs of weight). Result--shimmy GONE. I can't get it to move at all I'm going to start adding weight back on to the bike, beginning with the front. I'll keep experimenting. The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. On Dec 13, 3:09 am, EricP ericpl...@aol.com wrote: Hey, I resemble that remark. 220 also. More a combination of not having more major hills to descend and being a natural born chicken. But, hey, we need the eggs. Actually those photos aren't scary to me. In fact, would be nice to have only that much snow on the ground. Could have been out riding this weekend. We received 17 inches in the latest storm. Side roads are still unplowed or at best two cars wide. With very compacted snow. For me, that's scary. Eric Platt St. Paul, MN On Dec 12, 10:06 pm, Kelly tkslee...@gmail.com wrote: Well being 220 lbs means gravity is my friend on the downhill. That 57 was scary with the wobble but have hit 65 mph on long straight shot that was solid smooth and not scary at all. The desire to go that fast has finally faded. I guess the adrenalin junky in me has settled down.. another good reason to sell the race bike and get the ahh.. :) But then the ride to starbucks and walgreens today was just as scary as that speed :)http://www.flickr.com/photos/tksleeper/sets/72157625582548862/ Kelly -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
On Mon, Dec 13, 2010 at 16:13, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. What kind of rear rack do you have? Based on your account, I'm guessing that an overly flexible rear rack is contributing to the shimmy problem on your bike. I really wouldn't expect a bike with the geometry and stout tubing of the Sam Hillborne to shimmy under less than extreme loading, and was surprised to read your account when you first brought it up. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
It's a Nitto R-14. The saddlesack large does flop around when you rock the bike, so the compliance that I think you are correctly seeking might be there as well. On Dec 13, 4:19 pm, james black chocot...@gmail.com wrote: On Mon, Dec 13, 2010 at 16:13, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. What kind of rear rack do you have? Based on your account, I'm guessing that an overly flexible rear rack is contributing to the shimmy problem on your bike. I really wouldn't expect a bike with the geometry and stout tubing of the Sam Hillborne to shimmy under less than extreme loading, and was surprised to read your account when you first brought it up. James Black Los Angeles, CA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I weigh about 175. The whole bike rig with both bags on it as described above is probably in the low 40s. So maybe 215 bike + cargo + rider. Straight medium. :) My bars are 1-2 inches above saddle height. On Dec 13, 4:21 pm, Seth Vidal skvi...@gmail.com wrote: On Mon, Dec 13, 2010 at 7:13 PM, William tapebu...@gmail.com wrote: The fundamental conclusion I can make already is that front end shimmy at moderate speed no-handed is not a fundamental property of this bicycle. It's a property of a particular configuration on this bicycle. If I don't like it, I can configure this bike differently. If I choose to configure my bike this way, I should be prepared to accept some shimmy. Jan's article encouraged me to experiment, and I've started doing that, and I'm learning more about my bike, and that's all good stuff. How much do you weigh + yourstuff? How Are the bars set up vis-a-vis the saddle? -sv -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
... at 57 mph in a turn I was afraid of that bike at speed ... Only thing crazier I've ever heard of was Arlo Gutherie riding his motorcycle down the mountain road... playin' his guitar... Geez, Kelly, STFD... gonna kill yourself. On Dec 11, 11:38 am, Kelly tkslee...@gmail.com wrote: I had an experiance with a high speed shimmy .. always over 50 mph and if I was trying to turn it was even worse. Tried everything. Giant eventually gave me a new frame .. only because they didn't have a matching fork for the frame I had.. in that case they believed it to be in the frame. It was pure torture.. I don't like being afraid of my bike, but after having it shimmy/shake at 57 mph in a turn I was afraid of that bike at speed. Another time at 63 mph. Headsets, wheels, tires, handle bars, stems.. seat adjustments.. what's worse the only way to test to see if it's fixed was to get back to that speed. After I got the new frame is was like night and day.. and relaized the bike had been loose or looser than the new one.. loose = not as stable even in those 30 40 mph turns as the new one.. I trying to say that means anything.. just saying I don't agree that shimmy is part of a bike or that we should have to suck it up. If a bike shimmy's it takes the fun and love for the bike away.. a deep gut renching saddness that the bike isn't what it should be. As a consumer a shimmy on a new bike is not acceptable to me. Period. I expect the answer to be found... in design or something. Later Kelly -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
So you're saying the harmonics of the guitar may stop the woble? Good thought there. :) -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ NRC
Your experience with a 1972 Paramount is interesting. I have a 1977 P-15 Paramount, that I'm still riding, and I've never experienced any problems with speed wobbles. It's a 26 frame bike with a 110mm extension on the stem. It's rock steady descending on steep roads with speeds attained of 45-55mph.. The only bike, that I've ridden, that exhibited a tendency toward speed wobbles was a 63 cm Pogliaghi Italcorse bike I purchased in 1974. It would occasionally develop a speed wobble riding on a level road, that I could dampen fairly easily by pressing one knee against the top tube. For some reason, it never developed a speed wobble while descending (and this was while I lived in Boulder, CO where there were many opportunities for fast descents!). It would interesting to know what combination of factors are attributable to a bike having a tendency for speed wobbles. Jim Cloud Tucson, AZ On Dec 12, 10:08 am, Steve Palincsar palin...@his.com wrote: On Sat, 2010-12-11 at 20:18 -0800, james black wrote: On Sat, Dec 11, 2010 at 04:59, Steve Palincsar palin...@his.com wrote: Knee to top tube is a highly effective and well known (in my experience) way to stop /speed wobble/ -- as distinguished from shimmy. And speed wobble happens with hands on the bars, in fact can be caused by those hands on the bar (death grip or shivering). In discussions about shimmy (of which there have been many over the years on this and other lists) I have often described a distinction between what I call speed wobble and what I call shimmy. Knee to top tube is effective on shimmy (meaning the oscillation one encounters riding no hands at normal cruising speeds of 15-20 mph), but it's hard to put a knee to top tube while pedaling, so this is of limited application (especially on a fixed gear bike). My 1972 P-15 Paramount had a terrifying speed wobble back when it was new. Clamping the top tube between my knees and trying my best to squeeze the bejeezus out of the tube did in fact stop the shaking. I subsequently changed the stem length and the speed wobble permanently stopped. The bike always felt marginally unstable on fast descents, though -- I used to describe it as holding my life in a little goldfish bowl by the fingertips, arms outstretched. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ NRC
It would interesting to know what combination of factors are attributable to a bike having a tendency for speed wobbles. Jim Cloud Tucson, AZ Which is the subject of the Shimmy Review in the Winter BQ! The Winter BQ recounts opinions and experiences from the past 100 years in a few pages, and points toward ways to reduce or eliminate the phenomenon. Subscribe, and you will not regret it! Well, I don't know that, but I haven't regretted it. I went ahead and got the whole set. If you do, too, you'll see how groups of riders, some of whom have considerable training in science, have been exploring French bicycles, yes, but also other than French bicycles, discovering and introducing a rich body of cycling knowledge that never made it to the mass market in the USA, but which was extremely influential, and promises further progress as we develop new materials and, I hope, a new society as we rebuild American cities and a better way of life...But, that is just my fond fantasy... -- Bill Gibson Tempe, Arizona, USA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ NRC
I concur with your opinion on the Paramount. I, too, have a few of the 26 bikes, all 531 , and find they are rock steady. Is this a 27 wheel thing maybe? Sent from my iPad On Dec 12, 2010, at 12:43 PM, Jim Cloud cloud...@aol.com wrote: Your experience with a 1972 Paramount is interesting. I have a 1977 P-15 Paramount, that I'm still riding, and I've never experienced any problems with speed wobbles. It's a 26 frame bike with a 110mm extension on the stem. It's rock steady descending on steep roads with speeds attained of 45-55mph.. The only bike, that I've ridden, that exhibited a tendency toward speed wobbles was a 63 cm Pogliaghi Italcorse bike I purchased in 1974. It would occasionally develop a speed wobble riding on a level road, that I could dampen fairly easily by pressing one knee against the top tube. For some reason, it never developed a speed wobble while descending (and this was while I lived in Boulder, CO where there were many opportunities for fast descents!). It would interesting to know what combination of factors are attributable to a bike having a tendency for speed wobbles. Jim Cloud Tucson, AZ On Dec 12, 10:08 am, Steve Palincsar palin...@his.com wrote: On Sat, 2010-12-11 at 20:18 -0800, james black wrote: On Sat, Dec 11, 2010 at 04:59, Steve Palincsar palin...@his.com wrote: Knee to top tube is a highly effective and well known (in my experience) way to stop /speed wobble/ -- as distinguished from shimmy. And speed wobble happens with hands on the bars, in fact can be caused by those hands on the bar (death grip or shivering). In discussions about shimmy (of which there have been many over the years on this and other lists) I have often described a distinction between what I call speed wobble and what I call shimmy. Knee to top tube is effective on shimmy (meaning the oscillation one encounters riding no hands at normal cruising speeds of 15-20 mph), but it's hard to put a knee to top tube while pedaling, so this is of limited application (especially on a fixed gear bike). My 1972 P-15 Paramount had a terrifying speed wobble back when it was new. Clamping the top tube between my knees and trying my best to squeeze the bejeezus out of the tube did in fact stop the shaking. I subsequently changed the stem length and the speed wobble permanently stopped. The bike always felt marginally unstable on fast descents, though -- I used to describe it as holding my life in a little goldfish bowl by the fingertips, arms outstretched. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ NRC
On Sun, 2010-12-12 at 14:40 -0500, Robert Zeidler wrote: I concur with your opinion on the Paramount. I, too, have a few of the 26 bikes, all 531 , and find they are rock steady. Is this a 27 wheel thing maybe? I do not recall a 1972 Paramount coming with 26 wheels. FWIW, mine had 27. The other option was tubulars. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
As long as they don't have harps, you're safe. (Bad joke, totally admit it.) Good for you for getting the bike up to 57. Have been up to 40 on the Sam Hillborne. Fast enough for me. No shimmy on that descent. Unless my knocking knees caused something. Eric Platt St. Paul, MN On Dec 12, 1:07 pm, Ken Freeman kenfreeman...@gmail.com wrote: Or those of the background singers? On Sun, Dec 12, 2010 at 12:28 PM, Kelly tkslee...@gmail.com wrote: So you're saying the harmonics of the guitar may stop the woble? Good thought there. :) -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.comrbw-owners-bunch%2bunsubscrib...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- Ken Freeman Ann Arbor, MI USA -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Well being 220 lbs means gravity is my friend on the downhill. That 57 was scary with the wobble but have hit 65 mph on long straight shot that was solid smooth and not scary at all. The desire to go that fast has finally faded. I guess the adrenalin junky in me has settled down.. another good reason to sell the race bike and get the ahh.. :) But then the ride to starbucks and walgreens today was just as scary as that speed :) http://www.flickr.com/photos/tksleeper/sets/72157625582548862/ Kelly On Dec 12, 7:27 pm, EricP ericpl...@aol.com wrote: As long as they don't have harps, you're safe. (Bad joke, totally admit it.) Good for you for getting the bike up to 57. Have been up to 40 on the Sam Hillborne. Fast enough for me. No shimmy on that descent. Unless my knocking knees caused something. Eric Platt St. Paul, MN On Dec 12, 1:07 pm, Ken Freeman kenfreeman...@gmail.com wrote: Or those of the background singers? On Sun, Dec 12, 2010 at 12:28 PM, Kelly tkslee...@gmail.com wrote: So you're saying the harmonics of the guitar may stop the woble? Good thought there. :) -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.comrbw-owners-bunch%2bunsubscrib...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- Ken Freeman Ann Arbor, MI USA- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ NRC
You sure he didn't mean a 26 frame size (not wheel size)? On Dec 12, 11:42 am, Steve Palincsar palin...@his.com wrote: On Sun, 2010-12-12 at 14:40 -0500, Robert Zeidler wrote: I concur with your opinion on the Paramount. I, too, have a few of the 26 bikes, all 531 , and find they are rock steady. Is this a 27 wheel thing maybe? I do not recall a 1972 Paramount coming with 26 wheels. FWIW, mine had 27. The other option was tubulars. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Two (hopefully quick) examples from my limited experience in the past few years. Worst shimmy ever had was on a 1st generation Kogswell that Esteban now owns. Would even shimmy when riding with both hands on the bars. A guess - my weight at the time acted to overload the bike causing the shimmy. Some day would love to ride that bike again and see if my losing 40 or so pounds from that time makes a difference. My Sam Hillborne had some tendency to shimmy in certain occasions. Even with Marathon Supreme tires. Earlier this summer had Hiawatha Cyclery install a Shimano 105 headset instead of the one that comes with the bike. Shimmy has stopped. A number of reasons that could be. No matter what, am even a happier camper with the bike. Still waiting for my BQ. Eric Platt St. Paul, MN On Dec 11, 1:13 am, CycloFiend cyclofi...@earthlink.net wrote: on 12/10/10 10:03 AM, William at tapebu...@gmail.com wrote: Since I'm growing convinced that there might not be anyone who really understands shimmy, I'm going to run some experiments of my own on my Hillborne to attempt to understand it more. Since that bike, in it's current state, shimmies willingly when riding no-handed at 15mph on a smooth flat road, I think I have a decent baseline and reasonably reproducable test environment. I'm going to try several (numerous?) things, and I'll at least try to take better than normal notes, and see if I can learn anything. There have been several significant discussions of shimmy on the iBob list reasonably recently and over the years. Ride buddy JimG has also documented his shimmy experiences and expermenting/troubleshooting with a non-Rivendell bicycle via his blog (which can be found viahttp://yojimg.net/bike) There are certainly variables he found to damp or reduce speed-specific oscillations. http://sfcyclotouring.blogspot.com/search?q=shimmy And just to mention too, that a general discussion of BQ articles is probably best discussed on a more general list. - Jim -- Jim Edgar cyclofi...@earthlink.net Cyclofiend Bicycle Photo Galleries -http://www.cyclofiend.com Current Classics - Cross Bikes Singlespeed - Working Bikes Gallery updates now appear here -http://cyclofiend.blogspot.com Then I sat up, wiped the water out of my eyes, and looked at my bike, and just like that I knew it was dead -- Robert McCammon, Boy's Life -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I had an experiance with a high speed shimmy .. always over 50 mph and if I was trying to turn it was even worse. Tried everything. Giant eventually gave me a new frame .. only because they didn't have a matching fork for the frame I had.. in that case they believed it to be in the frame. It was pure torture.. I don't like being afraid of my bike, but after having it shimmy/shake at 57 mph in a turn I was afraid of that bike at speed. Another time at 63 mph. Headsets, wheels, tires, handle bars, stems.. seat adjustments.. what's worse the only way to test to see if it's fixed was to get back to that speed. After I got the new frame is was like night and day.. and relaized the bike had been loose or looser than the new one.. loose = not as stable even in those 30 40 mph turns as the new one.. I trying to say that means anything.. just saying I don't agree that shimmy is part of a bike or that we should have to suck it up. If a bike shimmy's it takes the fun and love for the bike away.. a deep gut renching saddness that the bike isn't what it should be. As a consumer a shimmy on a new bike is not acceptable to me. Period. I expect the answer to be found... in design or something. Later Kelly -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Shimmy,shimmy,cocoa pop On Dec 10, 1:03 pm, William tapebu...@gmail.com wrote: I am a recent subscriber of Bicycle Quarterly. I had thought about subscribing for a while, and two things about the newest issue made me pull the trigger. One was the write up about the Bilenky 650B tandem (dude, I want one). The other was the article about shimmy. I know Jan Heine has a reputation under some sections of the big tent of cycling, and I was interested to hear what he had to say. I expected by now somebody would have started a thread about the shimmy article, but it is towards the back. My Samuel Hillborne is the first bike I've owned that has a pronounced tendency to shimmy when riding no- handed. I'm not the most experienced rider. I've only had 30 or 40 different bikes in my lifetime, so I don't have nearly the experience Jan does. I hoped to gain a greater understanding of the problem and maybe do something about it on my Sam. Unfortunately, I found the article almost entirely unsatisfying. The Cliff-notes synopsis is: I don't know what causes shimmy, nor does anyone else. Here's what several oldschool guys said about shimmy. They were wrong. I can't take a bike that doesn't shimmy and change it into a bike that does shimmy. Even though I don't have any ideas about the causes or the solutions, you should absolutely swap your headset to needle bearings if your bike shimmies and hope for the best, even though I don't know if it will help, and maybe will make it worse Now don't get me wrong. I don't understand shimmy, but I came to the article with the attitude of student. The only other articles I've read on the topic are Sheldon Brown's (RIP) very brief glossary discussion and the Jobst Brandt article. For Jan to put the single word Shimmy on the cover, and to title his article What Causes Shimmy? suggests that he knows something. The article content itself suggests to me that Jan might not know any more about shimmy than any of us. That's not necessarily a bad thing: I'm convinced it's a complex problem. But I'd almost rather see a person in a pedagogical position of leadership to say Hey, I know a lot, but I don't understand shimmy. Here's some anecdotal observations I've made. Here's some anecdotes I've heard, but haven't verified. and just end it there. Since I'm growing convinced that there might not be anyone who really understands shimmy, I'm going to run some experiments of my own on my Hillborne to attempt to understand it more. Since that bike, in it's current state, shimmies willingly when riding no-handed at 15mph on a smooth flat road, I think I have a decent baseline and reasonably reproducable test environment. I'm going to try several (numerous?) things, and I'll at least try to take better than normal notes, and see if I can learn anything. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
William, I am sorry you are disappointed with our article on shimmy. We tried to offer summary of the factors that appear to cause or exacerbate shimmy. After all, we know that some bikes rarely shimmy (heavy tubes, long trail, no load, skinny tires). It appears that shimmy is a multi- faceted problem with more than one cause and more than one solution. To provide a complete picture, we presented other opinions on the issue, which may help you in your own research... I find it fascinating what people thought about these things 50 or 70 years ago. Most of all, we felt the need to publish this article, because we very much like bikes with optimized handling, wide supple tires, relatively flexible tubing, etc. The one downside of these bikes is a greater tendency to display shimmy. Of course, your Sam Hillborne shows that even bikes that are very different also can display persistent shimmy. And none of our favorite bikes shimmies a lot, so low trail, front loads, wide supple tires and relatively flexible tubing don't automatically result in a bike that shimmies. I am beginning to believe that all bikes have a tendency to shimmy, and depending on a number of factors, the oscillations either are dampened or self- reinforce. For your bike, if you don't already have a needle-bearing headset, I'd give it a try. That is the only thing we have found to work consistently in curing shimmy or at least reducing it so that it appears only rarely. You may also try to switch to narrow, stiff tires, but there are downsides to that. If you are carrying a load on your bike, you could try using a backpack (with its own downsides). It's hard to change the tubing or geometry of your bike... I don't know what you expected in the article, but I would like to remind you that we offer a money-back guarantee for the unused portion of your subscription. And if your experiments yield something conclusive, please let us know. We'd love to publish your experiences as an additional piece to the puzzle. Jan Heine Editor Bicycle Quarterly http://www.bikequarterly.com Follow our blog at http://janheine.wordpress.com/ -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
On Fri, 2010-12-10 at 10:29 -0800, Jan Heine wrote: I am beginning to believe that all bikes have a tendency to shimmy, and depending on a number of factors, the oscillations either are dampened or self-reinforce. Which is exactly what Jobst Brandt says in the rec.bicycles.tech FAQ. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
OK, hoping not to spoil for folks who haven't seen the article yet- I thought it was a decent survey of plausible causes for shimmy.It didn't reveal a catch-all cure for the problem, but that's probably b/ c none could possibly exist, since there are so many possible causes, some of them combining with each other.BTW if you're going to try the needle-bearing route, I think velo orange has them now(?) whereas they were getting scarce before. Anyway good luck with sorting out the on your rivendell. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Jan I'm extremely flattered at your almost instant reply. I don't know if that means you regularly read the list or if somebody you know does. I admire your work deeply and endorse your publication enthusiastically. Every copy of BQ I've seen has had something astonishing for me. This issue was no different. I am pleased to be a subscriber. Regarding shimmy, it's possible that my expectations were unrealistic. I thought I'd learn some conclusive, empirically testable conclusions, and I didn't get that. That being the state of things, I'm motivated now to experiment myself. I'm certain that you encourage that, and your article actually has helped urge me to do that which I think is a positive outcome. The things that 100% can agree upon is that shimmy is an oscillation. For that reason, it is easy to assume that there should be a spring +mass+damper model that can be used to understand the system. Whatever that system is, we can also agree, I think, that there exists some excitation force is acting on that system and making it oscillate. The missing piece in the few articles I've read prior to yours is a failure to establish and define what any of these things even are. What is the spring? You argue that it is the flexing torsion of the frame, but then concede that both the stiff frames you hate nor the flexy frames you love both don't shimmy. You imply that tire flex has something to do with the system, but it's not clear to me whether you think it's part of the spring, the mass, the damper, the exitation force, a combination, or all four. What is the mass? Some suggest that it is only the steering parts, others state it is everything including rider and the rear part of the bike. What's the damper? You argue that it's the stuff that hinders rotation: headset plus riders hands, and indirectly the riders leg squeezing the top tube. J. Brandt says tire tread is also a significant damper. Regarding the excitation force, there is no consensus of what it is or where it comes from. Sheldon(RIP) said it came from the back end of the bike, J. Brandt says it comes from the spinning wheel and sometimes from the natural frequency of human shivering. You, I think, allow it to be anything, since it is the amplifying or attenuating property of the system that is important, hence the artificial whacking the top tube to get it going. If there isn't even consensus on what the system is, then there is no hope to formally construct a comprehensive understanding of that system. It very well may be that shimmy is just a property of a bike+rider system that is the unknown functional combination of numerous unmeasurable variables. If that's the real answer, then maybe you're recommendation is the only one that works: If your bike shimmies, change something If it got better, be happy or change the same thing even more If it got worse, change the same thing in the other direction If it stayed the same, change something else Again, my opinions about whether or not your article not meets my expectations does not reflect on the quality of your contributions to the cycling world. I hoped that your article starts a dialogue that gets the topic driven to a more satisfying scientific understanding. It all strikes me as voodoo right now. With all due respect, this needle bearing headset thing, especially, strikes me as voodoo. Bill On Dec 10, 10:29 am, Jan Heine hein...@earthlink.net wrote: William, I am sorry you are disappointed with our article on shimmy. We tried to offer summary of the factors that appear to cause or exacerbate shimmy. After all, we know that some bikes rarely shimmy (heavy tubes, long trail, no load, skinny tires). It appears that shimmy is a multi- faceted problem with more than one cause and more than one solution. To provide a complete picture, we presented other opinions on the issue, which may help you in your own research... I find it fascinating what people thought about these things 50 or 70 years ago. Most of all, we felt the need to publish this article, because we very much like bikes with optimized handling, wide supple tires, relatively flexible tubing, etc. The one downside of these bikes is a greater tendency to display shimmy. Of course, your Sam Hillborne shows that even bikes that are very different also can display persistent shimmy. And none of our favorite bikes shimmies a lot, so low trail, front loads, wide supple tires and relatively flexible tubing don't automatically result in a bike that shimmies. I am beginning to believe that all bikes have a tendency to shimmy, and depending on a number of factors, the oscillations either are dampened or self- reinforce. For your bike, if you don't already have a needle-bearing headset, I'd give it a try. That is the only thing we have found to work consistently in curing shimmy or at least reducing it so that it appears only rarely. You may also try to switch to narrow, stiff tires, but there
Re: [RBW] Re: Shimmy, according to BQ
On Fri, 2010-12-10 at 11:04 -0800, newenglandbike wrote: OK, hoping not to spoil for folks who haven't seen the article yet- I thought it was a decent survey of plausible causes for shimmy.It didn't reveal a catch-all cure for the problem, but that's probably b/ c none could possibly exist, since there are so many possible causes, some of them combining with each other.BTW if you're going to try the needle-bearing route, I think velo orange has them now(?) whereas they were getting scarce before. Anyway good luck with sorting out the on your rivendell. The VO 1 threaded roller bearing headset is in fact in stock right now, $36. http://store.velo-orange.com/index.php/components/headsets/vo-roller-bearing-headset-1-threaded.html -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
BTW, there's the Bicycle Quarterly Reader's Review list, http://groups.google.com/group/bqrr , that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list,http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
The shimmy article was OK. In general, I'm not a fan of every BQ article I read, but BQ is the only publication I read cover to cover every time. FWIW the two fender articles alone make buying a copy worthwhile. On Dec 10, 2:07 pm, William tapebu...@gmail.com wrote: Jan I'm extremely flattered at your almost instant reply. I don't know if that means you regularly read the list or if somebody you know does. I admire your work deeply and endorse your publication enthusiastically. Every copy of BQ I've seen has had something astonishing for me. This issue was no different. I am pleased to be a subscriber. Regarding shimmy, it's possible that my expectations were unrealistic. I thought I'd learn some conclusive, empirically testable conclusions, and I didn't get that. That being the state of things, I'm motivated now to experiment myself. I'm certain that you encourage that, and your article actually has helped urge me to do that which I think is a positive outcome. The things that 100% can agree upon is that shimmy is an oscillation. For that reason, it is easy to assume that there should be a spring +mass+damper model that can be used to understand the system. Whatever that system is, we can also agree, I think, that there exists some excitation force is acting on that system and making it oscillate. The missing piece in the few articles I've read prior to yours is a failure to establish and define what any of these things even are. What is the spring? You argue that it is the flexing torsion of the frame, but then concede that both the stiff frames you hate nor the flexy frames you love both don't shimmy. You imply that tire flex has something to do with the system, but it's not clear to me whether you think it's part of the spring, the mass, the damper, the exitation force, a combination, or all four. What is the mass? Some suggest that it is only the steering parts, others state it is everything including rider and the rear part of the bike. What's the damper? You argue that it's the stuff that hinders rotation: headset plus riders hands, and indirectly the riders leg squeezing the top tube. J. Brandt says tire tread is also a significant damper. Regarding the excitation force, there is no consensus of what it is or where it comes from. Sheldon(RIP) said it came from the back end of the bike, J. Brandt says it comes from the spinning wheel and sometimes from the natural frequency of human shivering. You, I think, allow it to be anything, since it is the amplifying or attenuating property of the system that is important, hence the artificial whacking the top tube to get it going. If there isn't even consensus on what the system is, then there is no hope to formally construct a comprehensive understanding of that system. It very well may be that shimmy is just a property of a bike+rider system that is the unknown functional combination of numerous unmeasurable variables. If that's the real answer, then maybe you're recommendation is the only one that works: If your bike shimmies, change something If it got better, be happy or change the same thing even more If it got worse, change the same thing in the other direction If it stayed the same, change something else Again, my opinions about whether or not your article not meets my expectations does not reflect on the quality of your contributions to the cycling world. I hoped that your article starts a dialogue that gets the topic driven to a more satisfying scientific understanding. It all strikes me as voodoo right now. With all due respect, this needle bearing headset thing, especially, strikes me as voodoo. Bill On Dec 10, 10:29 am, Jan Heine hein...@earthlink.net wrote: William, I am sorry you are disappointed with our article on shimmy. We tried to offer summary of the factors that appear to cause or exacerbate shimmy. After all, we know that some bikes rarely shimmy (heavy tubes, long trail, no load, skinny tires). It appears that shimmy is a multi- faceted problem with more than one cause and more than one solution. To provide a complete picture, we presented other opinions on the issue, which may help you in your own research... I find it fascinating what people thought about these things 50 or 70 years ago. Most of all, we felt the need to publish this article, because we very much like bikes with optimized handling, wide supple tires, relatively flexible tubing, etc. The one downside of these bikes is a greater tendency to display shimmy. Of course, your Sam Hillborne shows that even bikes that are very different also can display persistent shimmy. And none of our favorite bikes shimmies a lot, so low trail, front loads, wide supple tires and relatively flexible tubing don't automatically result in a bike that shimmies. I am beginning to believe that all bikes have a tendency to shimmy, and depending on a number of
[RBW] Re: Shimmy, according to BQ
Funny, Bill, that you say your Hillborne shimmied. The one I had (now sold) was the most stable bike I've ever ridden with no hands in my life. I could have had a 3 course dinner while riding and not even think about touching the bars. I had the standard Riv supplied Tange headset and even with Schwalbe Smart Sams ( a knobbie tire) it was smooth as glass. The replacement bike, a used Ram, is not as stable, but is more like other bikes I've had. Neither bike has any shimmy at all. I did own, for a while, a Cotic Roadrat , but that baby was shimmy city and was sold quickly. On that bike a headset change quieted it as did a tire switch. But I could not get rid of it. I even think the size and shape of the rider could influence it dynamically as much as bike geometry and even things like tire tread pattern. As others have mentioned above, shimmy is a complex set of factors, and due to system (bike/rider) to system variation it can affect one of identical bikes and not the other. ~Mike~ On Dec 10, 11:18 am, William tapebu...@gmail.com wrote: Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list,http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Allan, thanks for that suggestion. Sure. And to clarify, since your a new sub and may not realize, it's the _Reader's_ list. Jan is also on the list and probably monitors it, much as he does here and elsewhere, but it is of the Reader's. There is no party line and polite criticism, is certainly free to post. Regards, -Allan -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Mike This is part of the voodoo feel to the whole thing. You can find an article that says knobbies damp out shimmy. You can find another that says knobbies supply the excitation force for shimmy. You can find another article that states that wide tires like knobbies are typically more compliant and therefore enable low frequency oscillations to be amplified by the system. My first few experiments are going to be: 1. Baseline the bike. Log initial condition of all independent variables that I might change. Attempt to measure the frequency and amplitude of the shimmy 2. Vary front tire pressure and ride. Note changes 3. Vary rear tire pressure and ride. Note changes 4. take reference weight (like maybe two full water bottles) and put them at various locations on the system and note any changes A. On front rack B. In H2O cages C. In jersey pocket D. On rear rack E. maybe elsewhere 5. Change tires 6. Change front wheel 7. Change rear wheel 8. Tighten headset or similarly damp steering 9. Load rear end heavily 10. Load front end heavily On Dec 10, 11:44 am, Michael_S mikeybi...@rocketmail.com wrote: Funny, Bill, that you say your Hillborne shimmied. The one I had (now sold) was the most stable bike I've ever ridden with no hands in my life. I could have had a 3 course dinner while riding and not even think about touching the bars. I had the standard Riv supplied Tange headset and even with Schwalbe Smart Sams ( a knobbie tire) it was smooth as glass. The replacement bike, a used Ram, is not as stable, but is more like other bikes I've had. Neither bike has any shimmy at all. I did own, for a while, a Cotic Roadrat , but that baby was shimmy city and was sold quickly. On that bike a headset change quieted it as did a tire switch. But I could not get rid of it. I even think the size and shape of the rider could influence it dynamically as much as bike geometry and even things like tire tread pattern. As others have mentioned above, shimmy is a complex set of factors, and due to system (bike/rider) to system variation it can affect one of identical bikes and not the other. ~Mike~ On Dec 10, 11:18 am, William tapebu...@gmail.com wrote: Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list,http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
With some exceptions (like life-threatening high-speed wobs, no thanks)... maybe it's time we just embrace the shimmy... it could just be our bikes telling us: Slow the F down... Put your damn hands back on the bars Get a trailer if you wanna haul sh** Turn off that awful music on your iPod, it's giving me the shimmies Get me some decent tires and a nice headset, you cheapskate Don't worry about it... It's what makes me ride so nicely at all other times I fully expect to discover a shimmy in my Bomba (at some point)... I'll try not to freak out... Happy Friday, everyone... I'm ready to shimmy myself... Peace, BB On Dec 10, 3:12 pm, William tapebu...@gmail.com wrote: Mike This is part of the voodoo feel to the whole thing. You can find an article that says knobbies damp out shimmy. You can find another that says knobbies supply the excitation force for shimmy. You can find another article that states that wide tires like knobbies are typically more compliant and therefore enable low frequency oscillations to be amplified by the system. My first few experiments are going to be: 1. Baseline the bike. Log initial condition of all independent variables that I might change. Attempt to measure the frequency and amplitude of the shimmy 2. Vary front tire pressure and ride. Note changes 3. Vary rear tire pressure and ride. Note changes 4. take reference weight (like maybe two full water bottles) and put them at various locations on the system and note any changes A. On front rack B. In H2O cages C. In jersey pocket D. On rear rack E. maybe elsewhere 5. Change tires 6. Change front wheel 7. Change rear wheel 8. Tighten headset or similarly damp steering 9. Load rear end heavily 10. Load front end heavily On Dec 10, 11:44 am, Michael_S mikeybi...@rocketmail.com wrote: Funny, Bill, that you say your Hillborne shimmied. The one I had (now sold) was the most stable bike I've ever ridden with no hands in my life. I could have had a 3 course dinner while riding and not even think about touching the bars. I had the standard Riv supplied Tange headset and even with Schwalbe Smart Sams ( a knobbie tire) it was smooth as glass. The replacement bike, a used Ram, is not as stable, but is more like other bikes I've had. Neither bike has any shimmy at all. I did own, for a while, a Cotic Roadrat , but that baby was shimmy city and was sold quickly. On that bike a headset change quieted it as did a tire switch. But I could not get rid of it. I even think the size and shape of the rider could influence it dynamically as much as bike geometry and even things like tire tread pattern. As others have mentioned above, shimmy is a complex set of factors, and due to system (bike/rider) to system variation it can affect one of identical bikes and not the other. ~Mike~ On Dec 10, 11:18 am, William tapebu...@gmail.com wrote: Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list,http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
I would suggest adjusting / slash tightening the headset, before I bought a new one. My Ebisu All Purpose frame had a very slight front end shimmy as soon as I put it together. After two years of riding, I became aware that the shimmy was very gradually getting worse. One day I checked the headset and discovered it had loosened considerably. I ride a lot of bad roads and I now suspect that the top nut had never been tightened enough and rattled loose. It's better now. Michael On Dec 10, 1:03 pm, William tapebu...@gmail.com wrote: I am a recent subscriber of Bicycle Quarterly. I had thought about subscribing for a while, and two things about the newest issue made me pull the trigger. One was the write up about the Bilenky 650B tandem (dude, I want one). The other was the article about shimmy. I know Jan Heine has a reputation under some sections of the big tent of cycling, and I was interested to hear what he had to say. I expected by now somebody would have started a thread about the shimmy article, but it is towards the back. My Samuel Hillborne is the first bike I've owned that has a pronounced tendency to shimmy when riding no- handed. I'm not the most experienced rider. I've only had 30 or 40 different bikes in my lifetime, so I don't have nearly the experience Jan does. I hoped to gain a greater understanding of the problem and maybe do something about it on my Sam. Unfortunately, I found the article almost entirely unsatisfying. The Cliff-notes synopsis is: I don't know what causes shimmy, nor does anyone else. Here's what several oldschool guys said about shimmy. They were wrong. I can't take a bike that doesn't shimmy and change it into a bike that does shimmy. Even though I don't have any ideas about the causes or the solutions, you should absolutely swap your headset to needle bearings if your bike shimmies and hope for the best, even though I don't know if it will help, and maybe will make it worse Now don't get me wrong. I don't understand shimmy, but I came to the article with the attitude of student. The only other articles I've read on the topic are Sheldon Brown's (RIP) very brief glossary discussion and the Jobst Brandt article. For Jan to put the single word Shimmy on the cover, and to title his article What Causes Shimmy? suggests that he knows something. The article content itself suggests to me that Jan might not know any more about shimmy than any of us. That's not necessarily a bad thing: I'm convinced it's a complex problem. But I'd almost rather see a person in a pedagogical position of leadership to say Hey, I know a lot, but I don't understand shimmy. Here's some anecdotal observations I've made. Here's some anecdotes I've heard, but haven't verified. and just end it there. Since I'm growing convinced that there might not be anyone who really understands shimmy, I'm going to run some experiments of my own on my Hillborne to attempt to understand it more. Since that bike, in it's current state, shimmies willingly when riding no-handed at 15mph on a smooth flat road, I think I have a decent baseline and reasonably reproducable test environment. I'm going to try several (numerous?) things, and I'll at least try to take better than normal notes, and see if I can learn anything. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
At last, a voice of reason! In a message dated 12/10/2010 4:21:39 P.M. Eastern Standard Time, montclairbob...@gmail.com writes: With some exceptions (like life-threatening high-speed wobs, no thanks)... maybe it's time we just embrace the shimmy... it could just be our bikes telling us: Slow the F down... Put your damn hands back on the bars Get a trailer if you wanna haul sh** Turn off that awful music on your iPod, it's giving me the shimmies Get me some decent tires and a nice headset, you cheapskate Don't worry about it... It's what makes me ride so nicely at all other times I fully expect to discover a shimmy in my Bomba (at some point)... I'll try not to freak out... Happy Friday, everyone... I'm ready to shimmy myself... Peace, BB On Dec 10, 3:12 pm, William tapebu...@gmail.com wrote: Mike This is part of the voodoo feel to the whole thing. You can find an article that says knobbies damp out shimmy. You can find another that says knobbies supply the excitation force for shimmy. You can find another article that states that wide tires like knobbies are typically more compliant and therefore enable low frequency oscillations to be amplified by the system. My first few experiments are going to be: 1. Baseline the bike. Log initial condition of all independent variables that I might change. Attempt to measure the frequency and amplitude of the shimmy 2. Vary front tire pressure and ride. Note changes 3. Vary rear tire pressure and ride. Note changes 4. take reference weight (like maybe two full water bottles) and put them at various locations on the system and note any changes A. On front rack B. In H2O cages C. In jersey pocket D. On rear rack E. maybe elsewhere 5. Change tires 6. Change front wheel 7. Change rear wheel 8. Tighten headset or similarly damp steering 9. Load rear end heavily 10. Load front end heavily On Dec 10, 11:44 am, Michael_S mikeybi...@rocketmail.com wrote: Funny, Bill, that you say your Hillborne shimmied. The one I had (now sold) was the most stable bike I've ever ridden with no hands in my life. I could have had a 3 course dinner while riding and not even think about touching the bars. I had the standard Riv supplied Tange headset and even with Schwalbe Smart Sams ( a knobbie tire) it was smooth as glass. The replacement bike, a used Ram, is not as stable, but is more like other bikes I've had. Neither bike has any shimmy at all. I did own, for a while, a Cotic Roadrat , but that baby was shimmy city and was sold quickly. On that bike a headset change quieted it as did a tire switch. But I could not get rid of it. I even think the size and shape of the rider could influence it dynamically as much as bike geometry and even things like tire tread pattern. As others have mentioned above, shimmy is a complex set of factors, and due to system (bike/rider) to system variation it can affect one of identical bikes and not the other. ~Mike~ On Dec 10, 11:18 am, William tapebu...@gmail.com wrote: Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list,http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
Re: [RBW] Re: Shimmy, according to BQ
wish I had my BQ already. On Fri, Dec 10, 2010 at 2:11 PM, bpus...@aol.com wrote: At last, a voice of reason! In a message dated 12/10/2010 4:21:39 P.M. Eastern Standard Time, montclairbob...@gmail.com writes: With some exceptions (like life-threatening high-speed wobs, no thanks)... maybe it's time we just embrace the shimmy... it could just be our bikes telling us: Slow the F down... Put your damn hands back on the bars Get a trailer if you wanna haul sh** Turn off that awful music on your iPod, it's giving me the shimmies Get me some decent tires and a nice headset, you cheapskate Don't worry about it... It's what makes me ride so nicely at all other times I fully expect to discover a shimmy in my Bomba (at some point)... I'll try not to freak out... Happy Friday, everyone... I'm ready to shimmy myself... Peace, BB On Dec 10, 3:12 pm, William tapebu...@gmail.com wrote: Mike This is part of the voodoo feel to the whole thing. You can find an article that says knobbies damp out shimmy. You can find another that says knobbies supply the excitation force for shimmy. You can find another article that states that wide tires like knobbies are typically more compliant and therefore enable low frequency oscillations to be amplified by the system. My first few experiments are going to be: 1. Baseline the bike. Log initial condition of all independent variables that I might change. Attempt to measure the frequency and amplitude of the shimmy 2. Vary front tire pressure and ride. Note changes 3. Vary rear tire pressure and ride. Note changes 4. take reference weight (like maybe two full water bottles) and put them at various locations on the system and note any changes A. On front rack B. In H2O cages C. In jersey pocket D. On rear rack E. maybe elsewhere 5. Change tires 6. Change front wheel 7. Change rear wheel 8. Tighten headset or similarly damp steering 9. Load rear end heavily 10. Load front end heavily On Dec 10, 11:44 am, Michael_S mikeybi...@rocketmail.com wrote: Funny, Bill, that you say your Hillborne shimmied. The one I had (now sold) was the most stable bike I've ever ridden with no hands in my life. I could have had a 3 course dinner while riding and not even think about touching the bars. I had the standard Riv supplied Tange headset and even with Schwalbe Smart Sams ( a knobbie tire) it was smooth as glass. The replacement bike, a used Ram, is not as stable, but is more like other bikes I've had. Neither bike has any shimmy at all. I did own, for a while, a Cotic Roadrat , but that baby was shimmy city and was sold quickly. On that bike a headset change quieted it as did a tire switch. But I could not get rid of it. I even think the size and shape of the rider could influence it dynamically as much as bike geometry and even things like tire tread pattern. As others have mentioned above, shimmy is a complex set of factors, and due to system (bike/rider) to system variation it can affect one of identical bikes and not the other. ~Mike~ On Dec 10, 11:18 am, William tapebu...@gmail.com wrote: Allan, thanks for that suggestion. On Dec 10, 11:10 am, Allan in Portland allan_f...@aracnet.com wrote: BTW, there's the Bicycle Quarterly Reader's Review list, http://groups.google.com/group/bqrr, that was created as a venue for precisely these types of discussions. Not saying you can't discuss the mag anywhere you please, just saying we'd really appreciate the discussion there. :-) Carry on, -Allan- Hide quoted text - - Show quoted text -- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.comrbw-owners-bunch%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.comrbw-owners-bunch%2bunsubscr...@googlegroups.com . For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en. -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at
[RBW] Re: Shimmy, according to BQ
10:1 he lurks here... On Dec 10, 10:38 am, Bruce fullylug...@yahoo.com wrote: Send this part off to Eben Weiss. He can always use good material.. From: William tapebu...@gmail.com The Cliff-notes synopsis is: I don't know what causes shimmy, nor does anyone else. Here's what several oldschool guys said about shimmy. They were wrong. I can't take a bike that doesn't shimmy and change it into a bike that does shimmy. Even though I don't have any ideas about the causes or the solutions, you should absolutely swap your headset to needle bearings if your bike shimmies and hope for the best, even though I don't know if it will help, and maybe will make it worse -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Whooee, take off for bike ride look what I missed! I'll read the entire thread but for the moment here's some Riv content to chew on: The Atlantis is arguably one of the most stable bikes made. With my normal collection of rackage and a moderate sized front bag that'll hold a few pounds, it's rock solid. By adding panniers in the wrong places, I can get frightening shimmies. The key is to put the weight in the right places and it's back to rock solid. This took some experimentation to sort out and I firmly believe, based on talking to numerous tourists with similar loads on a variety of bikes, that personal riding style has a lot to do with it. Playing with the weight placement is the key to stability. Another list member had a Hillborne that scared the daylights out of him when he added the same front bag that I use daily. Remove bag, no shimmy. Add bag, death wobble. I submit that just these 2 data points point out the complexity of the issue. dougP On Dec 10, 3:12 pm, cyclotour...@gmail.com cyclotour...@gmail.com wrote: 10:1 he lurks here... On Dec 10, 10:38 am, Bruce fullylug...@yahoo.com wrote: Send this part off to Eben Weiss. He can always use good material.. From: William tapebu...@gmail.com The Cliff-notes synopsis is: I don't know what causes shimmy, nor does anyone else. Here's what several oldschool guys said about shimmy. They were wrong. I can't take a bike that doesn't shimmy and change it into a bike that does shimmy. Even though I don't have any ideas about the causes or the solutions, you should absolutely swap your headset to needle bearings if your bike shimmies and hope for the best, even though I don't know if it will help, and maybe will make it worse- Hide quoted text - - Show quoted text - -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
[RBW] Re: Shimmy, according to BQ
Jan Again, I appreciate your thoughts, and your massive contributions. I'll post findings once I have findings to post. Have a great weekend On Dec 10, 5:42 pm, Jan Heine hein...@earthlink.net wrote: On Dec 10, 11:07 am, William tapebu...@gmail.com wrote: With all due respect, this needle bearing headset thing, especially, strikes me as voodoo. It may be voodoo, but so far, it's worked in 100% of the cases we've tried. Mark's Ti Cycles shimmied terribly once he added a handlebar bag, as soon as he took his hands off the bars. With a needle bearing headset, it only shimmied at 24-26 mph when pedaling at 90-110 rpm no- hands. His Goodrich shimmied less, but still annoyingly so at speeds of 18-22 mph no-hands. It doesn't any longer with a needle bearing headset. After we published this, a reader also changed their headset, and also got rid of their shimmy. Furthermore, we've never had a test bike with a needle bearing headset that had significant shimmy issues, and we've also never had a 650B low-trail front-loading test bike with a ball-bearing headset that did NOT have shimmy. It seems that Chris King headsets, for all their other virtues, are more likely to shimmy. Furthermore, several people, including myself, have experienced shimmy with loose headsets, which went away when the headset was tightened. So clearly, headsets CAN be a component that allows shimmy to develop or conversely, attenuates it. So all I am reporting is a trend, and a hypothesis why this may work. It may be just chance, and on your bike, it may not work, nor on the next 20 bikes we test, and it may turn out a blind alley after all. But it's worth a try, as it's inexpensive and easy to do, with no downsides at all. Jan Heine Editor Seattle WA 98121http://www.bikequarterly.com Follow our blog athttp://janheine.wordpress.com/ -- You received this message because you are subscribed to the Google Groups RBW Owners Bunch group. To post to this group, send email to rbw-owners-bu...@googlegroups.com. To unsubscribe from this group, send email to rbw-owners-bunch+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en.
