John: That sounds like an ever so slight imbalance in the tire and / or wheel, that when mounted in just-the-wrong orientation, may be the cause. Mounting the tire with the label at the valve (common practice to locate punctures) gives you a starting point. Shimmy? Rotate the tire 90 or 180 degrees, then re-test. Perhaps in remounting the tire was moved just enough to smooth things out. In any case, it sounds like progress.
dougP On Monday, April 22, 2013 4:48:18 PM UTC-7, john wrote: > > Well, here's an interesting situation! > > I decided to take on the wheel issue first. I rode a very shallow hill at > perhaps 10 mph, no handed, sitting up. The shimmy was pronounced. Enough so > that I turned around, went back up the gentle grade, and tried again. Once > again, as the bike picked up a bit of speed, the shimmy returned. I turned > around, rode back up, did it again. And the shimmy returned. > > So I rode home, took the new tire off the new wheel, and installed it on > my old wheel. I went back to the same spot and tried again. The first time > down, at the same pace, on the same road, same lack of wind: no shimmy. I > tried it again: no shimmy. And again: no shimmy. > > Eureka! I thought. It must be the wheel. Well, this being my day off, I > took a good long flat ride on mixed terrain with that old wheel. Fantastic > few hours out on the bike. I'm really loving the Jack Browns - > surprisingly, as much or more so off pavement as on. > > This late afternoon, the wind had picked up considerably. Just to make > sure I had solved the riddle, I removed the tire, installed it on the new > wheel, went back to the same spot, and tried the test again: no shimmy. I > did it once, twice, three times. No shimmy. Went to different areas which > were a bit less windy: no shimmy. > > So now I can't reproduce the shimmy. Maybe the tire wasn't seated as well > as it could have been on the first trial? Maybe riding in wind has > something to do with it? > > I'll try again tomorrow morning. Hopefully the wind will have abated. > > On Monday, April 22, 2013 10:55:24 AM UTC-7, Dave Rivbike wrote: >> >> Hi John, If it's only happening when going no hands... the problem might >> be not ENOUGH weight (you) on the front of the bike. Your body is the >> engine, but it's also part of the steering and suspension. It's like taking >> the shock absorbers off your '64 Impala lowrider and bouncing around at >> inersections >> >> On Sunday, April 21, 2013 7:46:47 PM UTC-7, john wrote: >>> >>> Hello All. >>> >>> I thought I'd get some ideas on a recent shimmy development. Here is the >>> scenario: >>> >>> Rider specs: >>> John >>> Height: 5'11" >>> Weight: 150 soaking wet >>> PBH: 88.9 >>> SH: apprx 78.5 cm >>> >>> I ride a 60 cm. Sam HIll. >>> >>> I Never experienced shimmy with the stock build: Shimano deore front >>> and rear hubs, Velocity synergy wheels, (35 cm panaracer pasella tires), >>> noodle handlebars, SKS Longboard fenders, etc. >>> I ride with a nitto mini front rack, nitro rear rack (the one for >>> saddlebag support, not panniers). I ride with a Baggins "Adam" saddlebag. >>> No front bag as yet because I haven't found one to fit the distance between >>> the front rack and handlebars (I'm not particularly interested in buying a >>> nitro F-15 rack, but instead covet a Berthoud rando bag - yet I don't know >>> if the 28cm size will fill the gap. ) >>> >>> Nothing unusual for a Rivendell. >>> >>> Now, for the recent developments: >>> Swapped the old wheel (Velocity Synergy) for a newly built Velocity >>> Synergy with dynohub (Shimano Alfine). Have a lightweight B&M Cyo light >>> attatched to the right (rider's right while riding) of the rack. Switched >>> from 35cm Panaracers to 33.3 Jack Brown Greens. Got the JBs to fit under >>> Hono because I had issues with the Longboards on two different sets: >>> (rubbing, chattering, due to inherent fleibility) . I also shortened the >>> stem just a hair, to see if doing so would help alleviate some forearm >>> discomfort I'd been having. (The old setup was stem height equidistant to >>> saddle height.) Now the stem height is slightly below saddle height. >>> That's it. >>> >>> >>> Now: experiencing some shimmy (and less overall feeling of stability) >>> while riding no hands sitting upright. This does not occur all the time, >>> but it's noticeable. The "response" doesn't happen all the time, but still, >>> it's there, and unnerving when it does. >>> >>> This "response" almost never happened with my old, original setup. >>> Frustrating! Because I much prefer dyno lighting for any number of reasons, >>> and wanted to run narrower tires to better fit underneath Honjo fenders, >>> which I much prefer to Longboards. My "upgrades" were plenty expensive, >>> too! And a pain in the neck, and time away from the bike. Still, I want >>> what I want: the best Riv ride possible. Is there an inherent compromise >>> here? Am I missing something? And if it is the new developments, where is >>> the problem? Stem height? Wheel weight? Tire width? >>> >>> Any comments? Clues? Suggestions? I'll continue to ride and see how it >>> goes, but honestly, as much as I like the changes I've made (except for the >>> need to run thinner tires with is not optimal for me), I'd go back to the >>> original set up if it meant the end to shimmy. I do not like to shimmy! >>> >>> Yes, obviously I will start with the easy stuff first. As in, I'll raise >>> the stem and see what happens (or doesn't). After that, I'm frustrated. >>> Very frustrated. >>> >>> Suggestions would be appreciated. Thanks. >>> >>> John >>> >> -- You received this message because you are subscribed to the Google Groups "RBW Owners Bunch" group. To unsubscribe from this group and stop receiving emails from it, send an email to rbw-owners-bunch+unsubscr...@googlegroups.com. To post to this group, send email to rbw-owners-bunch@googlegroups.com. Visit this group at http://groups.google.com/group/rbw-owners-bunch?hl=en-US. 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