Re: Could This Be Loose Headset?

Tony Raven said:

Sounds like shimmy - a common but not well understood problem.

It does sound like shimmy, but then so did Behemoth's problem. Also
Brandt says this happens when one is coasting without hands, something I
have never done in my life, being still incapable of removing even one
hand from the bars for a fraction of a second.

My problem is aggravated, not relieved, by pedaling. Also, it seems to
help to lean forward somewhat.

And I don't remember Flyzipper shimmying in November ...

EFR
Ile de France

Elisa Francesca Roselli said:

Tony Raven said:

Sounds like shimmy - a common but not well understood problem.

It does sound like shimmy, but then so did Behemoth's problem. Also
Brandt says this happens when one is coasting without hands, something I
have never done in my life, being still incapable of removing even one
hand from the bars for a fraction of a second.

My problem is aggravated, not relieved, by pedaling. Also, it seems to
help to lean forward somewhat.

And I don't remember Flyzipper shimmying in November ...

Riding without hands isn't a requirement for shimmy - it just
exacerbates the problem. Holding the bars too tight can also encourage
it as can pedalling. Have you changed anything since November? Have the
frame pivots loosened? New tyres? Going faster as you get more
confident with it?

When it starts next time while you are not pedalling, with one pedal
down, move your leg to rest on the frame on one side and see if that
damps it out as a starter.

Shimmy can be very difficult to track down and solve.

Tony

Elisa Francesca Roselli said:

It does sound like shimmy

It does to me too. A loose headset won't cause any kind of shimmy. In
fact I'm deliberately using a slightly loose headset (because it or frame
has something wrong with that I can't be bothered to fix) and it doesn't
cause any problems besides the odd clunk over a bump, and possibly
increased bearing wear. In any case, you can tell if a headset is loose
(on a bike without front suspension, and with good brake properly tight)
by feeling for play (movement) when rocking the bike back and forth hard
with the front brake on hard.

If I couldn't live with it*, I would try altering weight distribution by
altering the riding position or rearranging any luggage. I used to get
shimmy with my tourer but it became less frequent after /slightly/
changing the handlebar stem and saddle positions, and completely
dissappeared after I completely rebuilt the bike with new components. Not
that I'm suggesting that you resort to the latter! Different size/weight
tyres may also cure it.

* When it happens, for a moment, try slowing down or weaving left to right
(used to work for me); it won't then necessarily come back when you speed
up again. Pressing a thigh/knee against the top tube is also supposed to
help.

~PB

Elisa Francesca Roselli said:

It does sound like shimmy, but then so did Behemoth's problem. Also
Brandt says this happens when one is coasting without hands,

"Usually", he says. It certainly can happen with hands on as well.

~PB

Quoted message said:

"Usually", he says. It certainly can happen with hands on as well.

"Shimmy that concerns riders the most occurs with hands firmly on the bars
and it is rider generated by muscular effect whose natural response is the
same as the shimmy frequency, about that of Human shivering. Descending in
cold weather can be difficult for this reason. The rider's "death grip"
only enhances the incidence of shimmy in this situation. Loosely holding
the bars between thumb and forefinger is a way of avoiding shimmy when
cold."

So to avoid it on a descent when you're shivering with fear, just relax and
loosely hold the bars between thumb and forefinger. Hmmmm. :-)

Pete Biggs said:

Quoted message said:

It does sound like shimmy

Quoted message said:

It does to me too. A loose headset won't cause any kind of shimmy.
In fact I'm deliberately using a slightly loose headset (because it
or frame has something wrong with that I can't be bothered to fix)
and it doesn't cause any problems besides the odd clunk over a bump,
and possibly increased bearing wear. In any case, you can tell if a
headset is loose (on a bike without front suspension, and with good
brake properly tight) by feeling for play (movement) when rocking
the bike back and forth hard with the front brake on hard.

The brake method usually works but sensing the clearance takes a finer
touch. As sloppy brake caliper will make its own clunk. A good
method to test (a non-suspension bicycle) for loose bearings is to
hold the bicycle by the handlebar stem and bounce the front wheel on
the ground. This generates a substantial vibration that will make
head bearing clearance and secondarily loose wheel bearings clatter.
BB looseness is easily felt by pulling and pushing laterally on one
pedal.

Quoted message said:

If I couldn't live with it*, I would try altering weight
distribution by altering the riding position or rearranging any
luggage. I used to get shimmy with my tourer but it became less
frequent after /slightly/ changing the handlebar stem and saddle
positions, and completely disappeared after I completely rebuilt the
bike with new components. Not that I'm suggesting that you resort
to the latter! Different size/weight tyres may also cure it.

I have not found that weight distribution changes anything and by that
I mean leaning forward and rearward. Adding baggage to the bicycle is
usually a damper and should change its response.

Quoted message said:

When it happens, for a moment, try slowing down or weaving left to
right (used to work for me); it won't then necessarily come back
when you speed up again. Pressing a thigh/knee against the top tube
is also supposed to help.

It does!

[email hidden]

Pete Biggs said:

Elisa Francesca Roselli said:

It does sound like shimmy

It does to me too. A loose headset won't cause any kind of shimmy. In
fact I'm deliberately using a slightly loose headset (because it or frame
has something wrong with that I can't be bothered to fix) and it doesn't
cause any problems besides the odd clunk over a bump, and possibly
increased bearing wear. In any case, you can tell if a headset is loose
(on a bike without front suspension, and with good brake properly tight)
by feeling for play (movement) when rocking the bike back and forth hard
with the front brake on hard.

If I couldn't live with it*, I would try altering weight distribution by
altering the riding position or rearranging any luggage. I used to get
shimmy with my tourer but it became less frequent after /slightly/
changing the handlebar stem and saddle positions, and completely
dissappeared after I completely rebuilt the bike with new components. Not
that I'm suggesting that you resort to the latter! Different size/weight
tyres may also cure it.

* When it happens, for a moment, try slowing down or weaving left to right
(used to work for me); it won't then necessarily come back when you speed
up again. Pressing a thigh/knee against the top tube is also supposed to
help.

~PB

Yes, weight distribution can have a strong effect on the tendency to
shimmy. When starting a solo, self-contained cross country tour a few
years ago, I discovered that the bike had severe shimmy. I was very
surprised and discouraged because I had been training for the tour with
bricks in all four panniers and had no such problem. I consulted with a
LBS near the beginning of the tour and they recommended changing the
headset. Of course, this didn't help. However, I soon discovered that
rearranging the pannier loading to be more evenly distributed side-to-side
and putting more weight in front took care of the problem.

LB

in message <[email hidden]>, Elisa Francesca

Roselli (') said:

Tony Raven said:

Sounds like shimmy - a common but not well understood problem.

It does sound like shimmy, but then so did Behemoth's problem. Also
Brandt says this happens when one is coasting without hands, something
I have never done in my life, being still incapable of removing even
one hand from the bars for a fraction of a second.

My problem is aggravated, not relieved, by pedaling. Also, it seems to
help to lean forward somewhat.

And I don't remember Flyzipper shimmying in November ...

Dynamic oscillation of the steering is essentially down to something
being excited harmonically, and that something is probably in the part
of the bike which turns with the headset (wheel, forks, handlebars).
Any weight (such as a bag or basket will change the harmonic frequency
by adding a pendulum effect. So if you currently do have a bar bag or
basket, try taking it off and seeing whether the oscillation still
occurs. If you don't have one, try putting one on (with a certain
amount of weight in it, of course).

Also - forgive me, but it seems from you posts that you may be a
somewhat nervous cyclist - your body forms part of the dynamic system.
If you are relaxed, your body will naturally tend to act as a damper,
reducing dynamic oscillation. But if you are very tense you may tend to
exacerbate it.

--
[email hidden] (Simon Brooke) http://www.jasmine.org.uk/~simon/

Morning had broken, and I found when I looked that we had run out
of copper roove nails.

Elisa Francesca Roselli said:

being still incapable of removing even one
hand from the bars for a fraction of a second.

Must make indicating problematical.

Tim

Tim Hall said:

Quoted message said:

being still incapable of removing even one hand from the bars for a
fraction of a second.

Quoted message said:

Must make indicating problematical.

Not so quick on the draw. Here is a rider that admits to having that
problem but many others dodge mentioning the problem. We didn't get
handlebar shift control for nothing. There were many riders who could
not shift their bicycles because they had with downtube shift levers.
The whole push to handlebar shifting came from many complaints from
people who could afford a more expensive bicycle especially if they
could shift it.

I doubt that hand signals have much to do with bicycle safety other
than left (right) turns in heavy (in left hand) traffic. I don't see
someone who has difficulty taking hands off the bars making such a
turn rather than finding a suitable signal controlled crossing or
waiting until traffic subsides.

[email hidden]

Quoted message said:

I doubt that hand signals have much to do with bicycle safety other
than left (right) turns in heavy (in left hand) traffic. I don't see
someone who has difficulty taking hands off the bars making such a
turn rather than finding a suitable signal controlled crossing or
waiting until traffic subsides.

Inability to signal, however, certainly enhances my nervousness and my
detestation of riding in traffic. There are many traffic intersections
that I don't even want to attempt. Of course, if I am stopped at the
light, I take that opportunity to signal like mad. But when I have to go
through on the green I can get nasty honks. Also I have to decide - pull
over to the right to get off the bike and cross as a pedestrian, or pull
over to the leftmost lane to attempt the left turn from there. Often I
make the wrong decision.

I'm looking forward to cycling in a group in the Netherlands this June
so as not to have to deal with these issues.

EFR
Ile de France

Elisa Francesca Roselli said:

Tony Raven said:

Sounds like shimmy - a common but not well understood problem.

It does sound like shimmy, but then so did Behemoth's problem. Also
Brandt says this happens when one is coasting without hands, something I
have never done in my life, being still incapable of removing even one
hand from the bars for a fraction of a second.

I know you can get the impression from that article, but lots of people
have shimmy while downhilling at speed, with hands on bars. Often the
shimmy is made worse by the death-grip you apply once shimmy starts.

Quoted message said:

My problem is aggravated, not relieved, by pedaling. Also, it seems to
help to lean forward somewhat.

Still consistent with shimmy.

Quoted message said:

And I don't remember Flyzipper shimmying in November ...

What's different now?

--

David L. Johnson

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