Could This Be Loose Headset?

On Sat, 2 Apr 2005 11:40:35 -0500, "Arthur Harris"
wrote:

"Elisa Francesca Roselli" wrote:
So could this wobble be due to a _loose_ headset? How does a loose
headset feel?

It's probably NOT a loose headset. To check for a loose headset: Stand next
to the bike. Grip the front brake lever tightly, and rock the bike forward
and back. If you hear or feel a "clunking," the headset is loose.

I believe an even better way to detect a too loose headset is a
variation of the above. Place the index finger of your free hand (the
one not holding the front brake lever) on the front of the
intersection between the lower headset cup (or the bottom of the head
tube on more "modern" bikes) and the fork crown. While rocking the
bike you can easily detect a mis-adjusted headset by any movement you
feel.


jeverett3ATearthlinkDOTnet http://home.earthlink.net/~jeverett3

Pete Biggs writes:

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.

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.

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.

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!

Mark who? writes:

At various times and on various bikes I have resolved/minimized a
front end shimmy by:

1. Reversing the front wheel in the dropouts

2. Shifting the saddle back on the seat post

3. Correctly lubricating and adjusting the headset

4. Relaxing my grip on the handlebars

5. Pressing my knee against the seat tube on long fast descents

6. Rearranging the gear on the front rack of a fully loaded touring bike.

In other words, shimmy is caused or aggravated by the interaction of
a bunch of different factors, and yes, headset adjustment can be one
of them. How you adjust your headset will depend on the headset
design. Older threaded headsets have two relatively large ( usually
32mm) nuts stacked one on top of the other, with a washer and/or
brake cable hanger stacked between them. Set the bearing pre-load
by adjusting the lower nut, then lock the lower nut in place by
tightening the upper nut with one wrench while holding the lower nut
in place with another wrench. Newer threadless headsets are held in
place by the handlebar stem, loosen the Allen bolts that hold the
stem onto the steerer tube and slide the stem up and down to change
the pressure on the headset bearings. The optimum set up for both
types of headset is the point where the handlebars turn freely, with
little or no resistance, but there is no up and down play in the
headset. This may not be possible with a worn headset, an
incorrectly installed headset, or a cheap, low quality headset.

An incorrectly installed headset may cause the bike to pull to the
left or right, which may or may not be aggravating the problem. I
spent almost 3 years wondering why I couldn't ride my Peugeot PX-10
in a straight line hands free, until the nice folks at Missing Link
(Berkeley's leading bike shop at the time) explained that the
headset was incorrectly installed.

Adding this last paragraph discredits your advice given above whether
that is apparent to you or not. Riding for years with a head bearing
with ball cages upside down is not something that would occur to
someone skilled in the art of bicycle maintenance and analysis of
dynamics.

On Sat, 2 Apr 2005 15:12:09 +0100, "Pete Biggs"
wrote:

Elisa Francesca Roselli wrote:

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 , Elisa Francesca
Roselli ') wrote:

Tony Raven wrote:

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.

--
(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.

On Sat, 02 Apr 2005 15:08:01 +0200, Elisa Francesca Roselli
wrote:

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


Must make indicating problematical.


Tim

Tim Hall writes:

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

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.

wrote:

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

wrote

Adding this last paragraph discredits your advice given above whether
that is apparent to you or not. Riding for years with a head bearing
with ball cages upside down is not something that would occur to
someone skilled in the art of bicycle maintenance and analysis of
dynamics.

Jobst.Brandt

I did not ride the bicycle with ball cages upside down, nor am I quite sure
how you inferred from my post that I did this. If I recall and understand
the explanation given to me when the problem was rectified in 1981 or '82,
the headset bearing races were not aligned correctly in the frame when the
bike was built.

By naming the make and model of bicycle involved, I thought I made it
apparent that this episode took quite a few years ago, at a time when most
bicycles were not assembled to especially high standards of alignment. Had I
known then what I know today, I undoubtedly would have bought the bike from
a different bike shop to start with, and possibly bought a different
bicycle.

I don't recall claiming to be skilled in "analysis of dynamics", nor am I
sure how you read such a claim into my post. The solutions I described were
arrived at through trial and error and a certain amount of intuition, not
through any systematic analysis. The random nature of the solutions I found
suggest a trial and error approach, not a systematic analysis.
--
mark

mark wrote:

I did not ride the bicycle with ball cages upside down, nor am I quite sure
how you inferred from my post that I did this.

I suspect it was the combination of your statement "until the nice folks
at Missing Link ... explained that the headset was incorrectly
installed." and the very limited number of ways you can incorrectly
install a headset and still have it work at all. Ball cages upside down
in the commonest and easiest.

Tony