Front wheel shimmy bike handling

Howard Neckel said:

I have experienced front wheel shimmy about four times,
always at high speed (over 40 mph), sometimes with cross
winds, sometimes not. I think the bike itself is pretty
solid --- that is, nothing wrong with
it. But from the posts, I'll have it double-checked for
spoke tension and headset adjustment.

But say I just have to live with it. Never going fast
is not an attractive option. So what should I do when
it occurs?

Try
- resting one of your knees against the top tube
- unweighting the saddle

see yarchive.netshimmy.htmlOpen ↗ for more info

--
Benjamin Lewis

The majority of the stupid is invincible and guaranteed for
all time. The terror of their tyranny, however, is
alleviated by their lack of consistency. -- Albert Einstein

I had trouble with this. Headset tested as properly
adjusted. It was a Stronglight roller bearing headset. Once
I changed the headset the problem went away. Maybe it was
something about the roller bearings and my inability to
evaluate proper adjustment or wear of bearings.

Gary Jacobson Rosendale, NY

"Benjamin Lewis" <[email hidden]> wrote in message
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Quoted message said:

Howard Neckel said:

I have experienced front wheel shimmy about four times,
always at high speed (over 40 mph), sometimes with cross
winds, sometimes not. I think the bike itself is pretty
solid --- that is, nothing wrong with
it. But from the posts, I'll have it double-checked for
spoke tension and headset adjustment.

But say I just have to live with it. Never going fast is
not an attractive option. So what should I do when it
occurs?

Try
- resting one of your knees against the top tube
- unweighting the saddle

see yarchive.netshimmy.htmlOpen ↗ for more info

--
Benjamin Lewis

The majority of the stupid is invincible and guaranteed
for all time. The terror of their tyranny, however, is
alleviated by their lack of

consistency.

Quoted message said:

-- Albert Einstein

there's tons on this subject in the google archives, but here's my
personal experience:

i had a shimmy-prone steel frame that had standard sized
tube. it was a bad & dangerous thing. i had another
identical geometry frame made, but with oversize steel tube.
it helped substantially. i later made a rear wheel with
straight gauge spokes on the drive side [thicker is stiffer
- an improvement in a heavily dished rear wheel.] it was
great in the second frame, and improved the shimmy in the
first. all other components, i.e. tires, tire pressures,
rims, etc. were identical.

the way i see it, shimmy is a function of the rider & their
weight reacting with the natural elasticity & therefore
resonance of the wheels & frame. if the two resonances of
wheel & frame coincide, you have a major problem. if they
can be tuned apart, either by frame change or wheel change,
it can be mitigated substantially.

if shimmy strikes, it can be stopped by the methods
mentioned by benjamin above, but imo, you're only making
progress if you can prevent it happening in the first place.

Howard Neckel said:

I have experienced front wheel shimmy about four times,
always at high speed (over 40 mph), sometimes with cross
winds, sometimes not. I think the bike itself is pretty
solid --- that is, nothing wrong with
it. But from the posts, I'll have it double-checked for
spoke tension and headset adjustment.

But say I just have to live with it. Never going fast is
not an attractive option. So what should I do when it
occurs? So far, an accident has not been inevitable (the
first four times), but I am scared [censored] and certain my
life is about to end. Do most people manage to retain
control? Are crashes actually rare?

I have been so scared I'm not sure how I handled it. I
remember telling myself "do not panic!". I bring my speed
back down, only using the rear brake. Most of the time I
bring the bike to a stop, so that my body can continue
"shimmying" in abject fear for a few minutes until I'm
ready to ride again. Though not particular religious,
sometimes I pray and thank God to be still alive.

Is it possible to control the bike while it is shimmying?
My worst experience was on a 50 mph descent, with a very
significant bend in the road just ahead of me. I was sure
I was going to go over the embankment. I stopped just
short of it.

The posts on the causes of shimmy are really interesting,
but the bottom line is surviving it. I'm interested in any
and all tips. Thanks!