Mike Murray

Steve Getsiv [mailto:ste-@ocfp.com] wrote:

"I think we could all benefit from a discussion of what can cause the

wobbles at high speed and the basics of checking your equipment thoroughly

prior to a 50mph+ descent."



Doug Evans [mailto:Dou-@sprbrk.com] wrote:

"Does anyone knows what causes the speed wobble phenomena? I haven't

experienced it myself, but I know someone who had to get off his bike to

remove and replace his wheels during a race, as his bike would get the

wobbles even at low speeds. Does it have something to do with natural

frequency?"



Adams, Mike [mailto:mad-@huttig.com]wrote:

"Check headset, wheel true, and frame alignment."



The causes of speed wobbles are discussed in this note:



http://draco.acs.uci.edu/rbfaq/FAQ/8h.5.html



Bad frame alignment, headset and wheel bearing adjustment do not cause

shimmy. Heavier or more high profile wheels can make shimmy more likely.

Longer, more flexible frames are more likely to shimmy (which is why I don't

need to worry about it). Braking does not stop it per se, however since it

is speed dependant and slowing will take you out of the range of speed that

causes shimmy. Simply putting a leg against the top tube will generally

stop it.



Mike Murray