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Shimmy on a descent-American Classic CR420(5 posts)

Shimmy on a descent-American Classic CR420dsweiss
Jul 17, 2003 7:23 PM
Tonight we were flying down a long descent > 40 mph. The bike started shimmying alittle and then violently and almost bucked me off. It is a Giant Team (2002-Aluminum). Bike is light (16.5 lbs). I weigh 155 lbs. This happenned once before on the same descent. The wheels are very flexible. Could that be the reason? I have been considering switching to Ksyrium

ANY IDEAS?
re: Shimmy on a descent-American Classic CR420russw19
Jul 17, 2003 8:20 PM
Those wheels shouldn't be flexible. If they are, they are not tensioned properly. Take them to a good shop and have them check the tension with a tensionometer. Also, check silly stupid things, like are your quick release skewers tight enough? Is the bearing preload set properly? Do you have a broken spoke or one that is very loose compared to the others?

Bottom line, if built right, those wheels shouldn't be flexy. If so, and they are new, send them to American Classic and ask them to rebuild them.

Russ
re: Shimmy on a descent-American Classic CR420Heron Todd
Jul 18, 2003 7:41 AM
Check out the rec.bicycles.tech FAQ on shimmy. I wouldn't assume it is the wheels.

Todd Kuzma
Heron Bicycles
LaSalle, IL 815-223-1776
http://www.heronbicycles.com
re: Shimmy on a descent-American Classic CR420dsweiss
Jul 18, 2003 8:13 AM
Thanks for the pointer to the article on Shimmy. So what does one do in this case. It makes it sound like resting your knee against the top tube is all you can do. Any other suggestions?
I read recently ...Uprwstsdr
Jul 18, 2003 10:27 AM
That keeping your feet in the 12/6 position, as opposed to 3/9 (on a clock) as people generally do, and weighting the pedal in the 6 position, as in a turn, will help reduce shimmy.