Michael's analysis and explanation is excellent; this from a former gear freak who used to tape little gear charts to my stem/ Speaking of multiple gears: I've ridden nothing but fixed and single for a number of years, but today I was toodling along on my daughter's new 3/4 size Townie 3i (thye 3 speed Nexus, aluminum version of the townie), and it is pretty nice to have a lower, headwind or hill gear or two; so I went out out and bought a 18 t bailout cog to supplement the 16 cruising cog (69").
On Sat, Jun 13, 2009 at 6:28 PM, MichaelH <mhech...@gmail.com> wrote: > > Darren, > > No. I am decidedly not talking about a shifting pattern where you have > to keep double shifting the front and rear derailers. I am talking > about simplifying the shifting pattern when you do have to shift the > front derailler. At the risk of overstating what you already know... > > There are 4 variable that must be considered when selecting gearing. > First, how wide a range do you want, second how much distance between > gears are you willing to tolerate, third, how much shifting do you > have to do to get from one gear to the next, and fourth, finally, what > are your individual preferences amongst the first three. I can't > speak at all to the last for you but can only encourage you to > consider all 4 in making decisions. > > I have a strong preference to have a fairly consistent difference of > about 10 % between gears and this eliminates the wide range cassetes > like the 8 spd 12x 32 you use. I use a 9 spd. 12x27. I also have a > strong preference to have a simple shifting pattern. Together, this > means i am forced to make some comprimises about how wide a range I > can use. When shifting between rings a difference of ten teeth will > generally put the next gear one rear shift away. This works well with > doubles but is too limiting for triples. So for triples I typically > use 46x36x26. Doubles get more complicated. I find that a difference > of 12 or 16 leaves me searching for the next gear, while a difference > of 14 puts me two cogs away from the next gear. > > Here's my favorite set up for a double: > > 12 13 14 15 17 19 21 24 27 > 48 108 100 93 86 76 68 62 54 X > 34 X 71 66 61 54 48 44 38 34 > > > This gives a pretty big high gear, a manageable low gear for most > situations and an easy shifting pattern. I can slide up or down the > cog set with about 10 % between gears and when I need to shift rings, > I can know that I am 2 cogs from the next gear, e.g from 54 down to 48 > or 62 down to 54. > > A 46 X 30 looks more complicated: > > 12 13 14 15 17 19 21 24 27 > 46 104 96 89 83 73 65 59 52 x > 30 x 62 58 54 48 43 39 34 30 > > The next gear is now three cogs away. E.G. from 59 to 54. > Certainly doable, but you might want to think about it before you go > that wide. > > Here's what a 44 X 30 looks like. > > 12 13 14 15 17 19 21 24 27 > 44 99 91 85 79 70 63 57 50 X > 30 X 62 58 54 48 43 39 34 30 > > In this case the two cog shift is a little more than my ideal of 10%, > (e. g. 50 to 43 or 54 to 63) but still perhaps acceptable. > > For me, I would be willing to give up one half gear at the top (99 vs > 104) to get a simpler shifting pattern. Others will disagree. > > BTW, there are web sites that can help in calculating gear ratios, but > its pretty easy to set up a spreadsheet like Numbers or Excel to do > this. The formualis simplify ( Ring/cog) X 27. This is an imperfect > approximation, but good enough for government work! > > Perfection is not reachable nor worth worrying about. Try what looks > like the best trade-off for you and change it if you feel you need to. > > Michael > > On Jun 12, 3:07 am, Darren Stone <dst...@bitmason.com> wrote: > > Hi Michael. I just read up on the White VBC road crank. It's quite > > beautiful also. It's a possibility. Thank you. > > > > I'm not sure if I'm understanding the 44-30 logic, but if it's to give > > a superior shift pattern that requires regular double shifts, then I > > may not enjoy it. I'm shooting for a wide-range double so I get a > > simple-minded "95% of the time ring", rowing through my 8 cogs (12-32) > > in the back, with a bail-out granny ring available when necessary. > > Mad up/down hills being the 5% exceptions that require double shifts. > > > > Singlespeeding has clearly rotted my brain!! I embrace any gear range > > now and don't care about step size! Thanks for doing the math, > > though; I appreciate it. It caused me to work through the > > possibilities again. On my Saluki, a 46-12 gives me 99 g.i. (it's > > shod with 650A) and even loaded up I think a 30-32 should be great for > > climbs. > > > > -Darren. > > > > On Jun 11, 5:43 pm, MichaelH <mhech...@gmail.com> wrote: > > > > > Two suggestions. Why don't you take a look at the White VBC crank > > > before you buy. They have a very low Q and lots of ring flexibility. > > > Second, one problem with a difference of 16 between rings is that once > > > you shift rings you are many cogs away from the next gear, and in fact > > > there really isn't a good pattern when you shift rings. A difference > > > of 14 will put you exactly two cogs away from the next gear of about + > > > or - 10 % almost anywhere on the cassette. So you might want to > > > consider a 44 / 30. You give up a couple of gear inches at the top, > > > but get a smoother pattern. A 30x32 is a small enough gear for most > > > riders to get up most hills without a touring load, and the 44x12 (99 > > > g.i.) will allow you to spin up to 30 mph; after that you can tuck > > > and coast. > > > > > Michael > > > > > On Jun 11, 3:58 pm, Darren Stone <dst...@bitmason.com> wrote: > > > > > > Hi. I have a tech crankarm/BB/spindle question that could use some > > > > expert insight. > > > > > > Current: Saluki w/ Sugino 50-40-26 triple & Phil BB. It's fine but > I > > > > definitely notice the "width"/tread/q-factor. My other rides are all > > > > singlespeeds, so that's to be expected. The triple is decadent but > > > > I'm seriously thinking about moving to a wide-range double. I spend > > > > most of my time in the 40 ring, likely in the 43 to 86 inch range. > > > > I've done the math and a 46-30 double might suit my riding needs. > I'd > > > > like to keep my 8 speed 12-32 XT cassette, Campy Record 9-speed > chain, > > > > and friction shift. It's all working well. > > > > > > So what I'm considering are the TA Pro 5 Vis cranks. Apparently, > > > > they're narrower than most cranksets so that's very appealing. > > > > Aesthetically, gorgeous. No reason to change the Phil BB, I assume. > > > > But what do I need to measure/scrutinize/order now before I make the > > > > switch? I understand chainline but some of the BB width and spindle > > > > length specs confuse me. > > > > > > Open to opinions. Cheers! > > > > > > -Darren. > > > -- Patrick Moore Albuquerque, NM Professional Resumes. Contact resumespecialt...@gmail.com --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. 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