Michael, Impeccable timing. Last weekend I was descending on my Rambouillet and noticed something similar (tires = 700x27 Rolly Poly). Above 35 mph, it's not exactly the shimmy/speed wobble you describe but an unnerving twitchiness/skittishness in the front end. At speeds of 40-50 mph descending 7 Colorado Rocky Mountain passes in 2008 the Rambouillet felt so consistently twitchy that I was anxious making even the slightest movements, like shifting hands from brake hoods to drops. Lowering the bars 2 cm hasn’t helped.
By comparison, the other bike that I've ridden for the past 12 years is a 1998 Cannondale T1000 touring bike with rake, trail and wheelbase specifically designed for loaded touring. This bike can descend any grade at any speed with any load with motorcycle-like confidence. I realize that there are dozens of variables that effect front-end stability (headset tightness, tires, wheels, rake, trail, wheelbase, rider’s fore/aft weight distribution, winds, rider skill/experience); I’d also be grateful to hear from others who experienced and then dialed down the twitchiness/speed wobble/shimmy factor. Will PS Michael, it sounds like you were going *really* fast. I’ve experienced such speed wobbles on motorcycles when going too fast, especially motorcycles without steering dampers. Once the shimmy was induced by a side wind; another due to irregular pavement. (Were either of these issues?) I also wonder if you were squeezing the top tube with your knees at the time (this is known to quell wobbles). On Aug 7, 5:37 pm, Jim Thill - Hiawatha Cyclery <thill....@gmail.com> wrote: > It'd be interesting to lower your stem a little and try again. > > On Aug 7, 2:37 pm, MichaelH <mhech...@gmail.com> wrote: > > > > > In five years of riding my Rambouillet I have never experienced any > > front end shimmy - until this morning. I was coming down VT 108 from > > Smugglers Notch and as the bike hit 45 mph I shifted my hands from the > > drops to the center, to get into a tuck, and all of a sudden I got > > this slight, but unnerving front end shimmy. As soon as I returned to > > the drops it quieted down. I have had this bike up to 50 before so it > > wasn't just the speed. Clearly, shifting my weight backwards seemed > > to unweight the front enough to cause the shimmy. I had an Acorn > > Rondoneur bag on the front but it didn't have much weight in it. > > > My son gave me a pair of Continental Grand Prix tires, which are only > > 23 mm and have proven to me that they need to be up around 110l bs to > > avoid pinch flats. That's the only difference I'm aware of. Has > > anyone else run a Rambouillet with very skinny tires, and did you > > experience any hi speed shimmy? > > > Other than that, I'm feeling pretty good that I can still make that > > climb (2800 ft up from my home). > > > BTW, as I started up the mountain road I ran into three heavily loaded > > senior citizens from, of all places, Walnut Creek! They spotted my > > bike right away. > > > michael -- 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.
