scroggs@uiucdcsp.UUCP (11/19/84)
Speed Wobble Troubles
Last spring, I purchased a custom frame through a reputable dealer from
a good company (King of Mercia built by Mercian of England). I took the
creation to the mountains of New Mexico, where I discovered that the bicycle
becomes unstable at speeds of about 28 miles per hour (a friend clocked me
while going down a hill). At 28 and above, the handlebars begin to oscillate,
and at about 32 mph I almost lost control of the bicycle. The frame has
'sport touring' dimensions. I noticed that placing weight in
my front panniers mounted on the low rider rack supresses the wobble,
allowing me to feel safe at speeds around 25-30 mph. I do
not consider myself a fast rider, but I do like to coast down moderate
hills without having to use the brakes for fear of losing control.
The dealer has assured me that the frame has no faults (like the
fork being out of alignment), and I have been unable to see any
problems with the machine.
Does anybody know the cause of these 'speed wobbles'? Does
anybody know of studies (scientific) which have tried to locate what
makes frames stable/unstable? Could a change of componets bring about
more stability?leimkuhl@uiucdcsb.UUCP (11/20/84)
My Holdsworth Special had a wobble thin the bars last springyear that was only noticeable when you I coasted "no hands" at speed. Since I Usuallydon't usually ride that way, I didn't bother to have it looked at until the end of the season. Turns out I needed a new forfrork(...now what the heck do ya call that thing...hmmm...tya know the dohicky ohicky that bearing and dohicky thatoohicky that hold the fork in... Ah nonow I remember--the headsetown). . Anyway, I haven't been out again thisince then to test it out. Could be that des despite the bad part the wobble's still there. I've heard that sometinmes large-size sport-touring bil kes have nasty wobbles (mine is 25.5"). -Ben Leimkuhler (uiucdcs!uiuccsb!leimkuhl)
neal@druxv.UUCP (Neal D. McBurnett) (11/21/84)
I had the same problem for quite a while, and tried lots of adjustments. I removed the reflector mounted in the spokes, I re-balanced my loads, etc, etc. The load re-balancing helped a little, but not enough. Finally a mechanic at the High Wheeler in Boulder tightened my HEADSET just a little, and that fixed it! -Neal McBurnett, ihnp4!druny!neal, 303-538-4852
bill@utastro.UUCP (William H. Jefferys) (11/25/84)
It's been a while since these were posted. Two articles on
bicycle stability:
David E. H. Jones, in *Physics Today*, April 1970, pp. 34-40
J. Lowell and H. D. McKell, in *American Journal of Physics*,
vol. 50, December 1982, pp. 1106-1112.
Finally, there is a book out, "Bicycling Science", by F. R. Whitt
and D. G. Wilson, MIT Press, 1982, which has extensive
discussions of the physics of bicycle stability.
--
"When evolution is outlawed, only outlaws will evolve"
Bill Jefferys 8-%
Astronomy Dept, University of Texas, Austin TX 78712 (USnail)
{allegra,ihnp4}!{ut-sally,noao}!utastro!bill (uucp)
bill%utastro.UTEXAS@ut-sally.ARPA (ARPANET)scroggs@uiucdcsp.UUCP (11/26/84)
Let me define the problem a little better-- Using a handlebar bag did make the problem a little worse. Using weight low in the front supressed almost all of the wobble (still, I don't carry much weight on short rides). Tightening the headset brought noticeable improvement, but did not cure the problem. Also, the headset is new, the one that came with the frame.
harris@uiucdcsb.UUCP (11/27/84)
Did you have a handlebar bag on the bike? Was there much stuff in it? That can definately cause that sort of problem. There have been numerous articles in Bicycling on how to load a bike for touring, and stability problems with loaded bikes, etc. I can't quote issue dates off the top of my head, though.
marcum@rhino.UUCP (Alan M. Marcum) (11/28/84)
Just because a bicycle is new is NOT grounds for assuming it is
properly adjusted. In addition, things like headsets and hub
bearings tend to loosen rather quickly when new, and may well
need re-adjusting. This is why a good bike shop wants to see
your bicycle within 2-4 weeks after purchase.
--
Alan M. Marcum Fortune Systems, Redwood City, California
...!{ihnp4, ucbvax!amd, hpda, sri-unix, harpo}!fortune!rhino!marcum