Shimmy

Quoted message said:

Steve Juniper wrote:

When going fairly fast front wheel shimmies (wheel turns a bit left and right fast back and forth)
when taking hands off handlebars. May be dangerous at speed. What causes it and how can it be
fixed (other than not taking hands off ;-) )? Thanks!
--
Steve Juniper ([email hidden])

First, please turn of the HTML. It is inappropriate for USENET.

Second, an answer to this question can be found in the FAQ
draco.acs.uci.edu8h.5.htmlOpen ↗

Steve Juniper said:

When going fairly fast front wheel shimmies (wheel turns a bit left and right fast back and forth)
when taking hands off handlebars. May be dangerous at speed. What causes it and how can it be
fixed (other than not taking hands off.

draco.acs.uci.edu8h.5.htmlOpen ↗

Jobst Brandt [email hidden] Palo Alto CA

Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an out
of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or wheels), even a
lopsided tire, etc. And/or any combination of the above.

Check these things, or have them checked, and corrected, where necessary.

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": geocities.comczcornerOpen ↗

Quoted message said:

Many things can cause shimmy. Frame alignment (mis-alignment, actually),

You had it right the first time, in a peculiar sort of way. A frame that's perfectly aligned is more
likely to shimmy than one that's out of whack. The bike, by itself, desires to turn only in one
direction. You're constantly applying force to make it go straight, and damping out its desire to
shimmy. Much easier to create a shimmy in a system where the bike wants to turn in either direction
with little effort.

I'm sure Jobst can put it more accurately than that, but he probably won't be as nice.

--Mike-- Chain Reaction Bicycles www.ChainReaction.com

"Chris Zacho "The Wheelman"" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an
out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or wheels),
even a lopsided tire, etc. And/or any combination of the above.

Check these things, or have them checked, and corrected, where necessary.

May you have the wind at your back. And a really low gear for the hills! Chris

Chris'Z Corner "The Website for the Common Bicyclist": geocities.comczcornerOpen ↗

Chris Zacho 'The Wheelman said:

Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an
out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or wheels),
even a lopsided tire, etc. And/or any combination of the above.

This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I know
now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true wheels do
not cause shimmy; any oscillations they would cause would be at a much higher frequency than shimmy
usually takes. Panniers might, actually, be relevant, but only because they change the overall
system response. Loose bearings are often cited as a cause, but there is no mechanism for them to
be involved.

Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only, the
shimmy I had was pretty predictable. The myths persist here because anything you might do will
change the system resonance enough to maybe change the speed at which shimmy would occur; often to a
speed you cannot reach.

Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is to
unload the saddle. It really works.

--

David L. Johnson

__o | As far as the laws of mathematics refer to reality, they are not _`\(,_ | certain, and as
far as they are certain, they do not refer to (_)/ (_) | reality. -- Albert Einstein

David L. Johnson said:

Chris Zacho 'The Wheelman said:

Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an
out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or wheels),
even a lopsided tire, etc. And/or any combination of the above.

This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I know
now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true wheels do
not cause shimmy; any oscillations they would cause would be at a much higher frequency than shimmy
usually takes. Panniers might, actually, be relevant, but only because they change the overall
system response. Loose bearings are often cited as a cause, but there is no mechanism for them to
be involved.

Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only, the
shimmy I had was pretty predictable. The myths persist here because anything you might do will
change the system resonance enough to maybe change the speed at which shimmy would occur; often to
a speed you cannot reach.

Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is to
unload the saddle. It really works.

a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
frames - Ъ×

dax said:

a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
frames - Ъ×

Try having the axle of *just* not quite seated properly on one side. Urgh.

Jasper

dax said:

David L. Johnson said:

Chris Zacho 'The Wheelman said:

Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an
out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or wheels),
even a lopsided tire, etc. And/or any combination of the above.

This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I
know now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true
wheels do not cause shimmy; any oscillations they would cause would be at a much higher frequency
than shimmy usually takes. Panniers might, actually, be relevant, but only because they change the
overall system response. Loose bearings are often cited as a cause, but there is no mechanism for
them to be involved.

Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only, the
shimmy I had was pretty predictable. The myths persist here because anything you might do will
change the system resonance enough to maybe change the speed at which shimmy would occur; often to
a speed you cannot reach.

Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is to
unload the saddle. It really works.

a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
frames - Ъ×

Hogwash.

Mark McMaster [email hidden]

Mark McMaster said:

dax said:

David L. Johnson said:

On Wed, 28 May 2003 18:24:30 -0400, Chris Zacho "The Wheelman" wrote:

>Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material, an
>out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or
>wheels), even a lopsided tire, etc. And/or any combination of the above.

This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I
know now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true
wheels do not cause shimmy; any oscillations they would cause would be at a much higher frequency
than shimmy usually takes. Panniers might, actually, be relevant, but only because they change
the overall system response. Loose bearings are often cited as a cause, but there is no mechanism
for them to be involved.

Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only, the
shimmy I had was pretty predictable. The myths persist here because anything you might do will
change the system resonance enough to maybe change the speed at which shimmy would occur; often
to a speed you cannot reach.

Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is to
unload the saddle. It really works.

a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
frames - Ъ×

Hogwash.

Mark McMaster [email hidden]

I speak from experience, Mark - Ъ×

dax said:

Mark McMaster said:

dax said:

On Wed, 28 May 2003 21:59:41 -0400, "David L. Johnson" <[email hidden]> wrote:

>On Wed, 28 May 2003 18:24:30 -0400, Chris Zacho "The Wheelman" wrote:
>
>
>
>>Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material,
>>an out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or
>>wheels), even a lopsided tire, etc. And/or any combination of the above.
>
>This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
>misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
>would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I
>know now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true
>wheels do not cause shimmy; any oscillations they would cause would be at a much higher
>frequency than shimmy usually takes. Panniers might, actually, be relevant, but only because
>they change the overall system response. Loose bearings are often cited as a cause, but there is
>no mechanism for them to be involved.
>
>Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only,
>the shimmy I had was pretty predictable. The myths persist here because anything you might do
>will change the system resonance enough to maybe change the speed at which shimmy would occur;
>often to a speed you cannot reach.
>
>Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is to
>unload the saddle. It really works.

a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
frames - Ъ×

Hogwash.

Mark McMaster [email hidden]

I speak from experience, Mark - Ъ×

So do I.

Mark McMaster [email hidden]

Mark McMaster said:

dax said:

Mark McMaster said:

dax wrote:

>On Wed, 28 May 2003 21:59:41 -0400, "David L. Johnson" <[email hidden]> wrote:
>
>
>
>>On Wed, 28 May 2003 18:24:30 -0400, Chris Zacho "The Wheelman" wrote:
>>
>>
>>
>>>Many things can cause shimmy. Frame alignment (mis-alignment, actually), poor frame material,
>>>an out of true wheel, Badly loaded panniers (if touring), loose bearings (either headset or
>>>wheels), even a lopsided tire, etc. And/or any combination of the above.
>>
>>This is a collection of myths. Fact is a properly aligned frame is more likely to shimmy than a
>>misaligned frame. What would be "poor" frame material? I had a classic lugged steel frame that
>>would shimmy on any fast downhill for me, which I replaced with a lighter, but otherwise (so I
>>know now) inferior aluminum frame which had 0 shimmy at any speed I could manage. Out of true
>>wheels do not cause shimmy; any oscillations they would cause would be at a much higher
>>frequency than shimmy usually takes. Panniers might, actually, be relevant, but only because
>>they change the overall system response. Loose bearings are often cited as a cause, but there
>>is no mechanism for them to be involved.
>>
>>Read the FAQ that Jobst mentioned. Although my experience was with my hands on the bars only,
>>the shimmy I had was pretty predictable. The myths persist here because anything you might do
>>will change the system resonance enough to maybe change the speed at which shimmy would occur;
>>often to a speed you cannot reach.
>>
>>Shimmy is a systemic response to the bike+rider as a whole. The quickest and cheapest cure is
>>to unload the saddle. It really works.
>
>
>a poorly made front wheel that is out of 'dish' will give a wicked speed wobble in the truest of
>frames - Ъ×

Hogwash.

Mark McMaster [email hidden]

I speak from experience, Mark - Ъ×

So do I.

Mark McMaster [email hidden]

have i got this straight? you took a front wheel, checked to make sure it was out of dish, put it in
a frame and fork you knew to be straight, took it up to a good speed - and had no problems? Think
about it - if the front wheel is not tracking in the same line as the rear, it will try to pull so
that it DOES track - yanking the fork over. Then the rear wheel goes back to where the frame wants
it to track - and the front wheel tries to follow THAT - but then the rear... you see what I mean?
SHIMMY SHIMMY SHAKE SHAKE. Ъ×

audaxrex snipes anonymously (in new English, no less):

Quoted message said:

have i got this straight? you took a front wheel, checked to make sure it was out of dish, put it
in a frame and fork you knew to be straight, took it up to a good speed - and had no problems?
Think about it - if the front wheel is not tracking in the same line as the rear, it will try to
pull so that it DOES track - yanking the fork over. Then the rear wheel goes back to where the
frame wants it to track - and the front wheel tries to follow THAT - but then the rear... you see
what I mean? SHIMMY SHIMMY SHAKE SHAKE. Ъ×

On bicycles that double track (leave two separate wet tracks after riding through a puddle) I found
no propensity to shimmy. The same goes for a front or rear wheel with a broken spoke (substantially
out of alignment). From what you say, and how you say it, I take it you are hypothesizing about all
this; common fare for wreck.bike.

"Think about it!"

Jobst Brandt [email hidden] Palo Alto CA

Quoted message said:

audaxrex snipes anonymously (in new English, no less):

Quoted message said:

have i got this straight? you took a front wheel, checked to make sure it was out of dish, put it
in a frame and fork you knew to be straight, took it up to a good speed - and had no problems?
Think about it - if the front wheel is not tracking in the same line as the rear, it will try to
pull so that it DOES track - yanking the fork over. Then the rear wheel goes back to where the
frame wants it to track - and the front wheel tries to follow THAT - but then the rear... you see
what I mean? SHIMMY SHIMMY SHAKE SHAKE. Ъ×

On bicycles that double track (leave two separate wet tracks after riding through a puddle) I found
no propensity to shimmy. The same goes for a front or rear wheel with a broken spoke (substantially
out of alignment). From what you say, and how you say it, I take it you are hypothesizing about all
this; common fare for wreck.bike.

"Think about it!"

Jobst Brandt [email hidden] Palo Alto CA

on my old Louison Bobet, I encountered a wicked speed-shimmy after installing a 'new' rebuilt
wheel... i suffered with this for most of the summer till i put a dishing tool on the wheel,
discovered the problem, corrected it - and the problem vanished and never returned. I also know from
fixing flats on motorcycles - returning a rear wheel to the bike, it is CRITICAL that the rear wheel
be centered, or it's speed-shimmy city. Now that's a REAR, and a MOTORCYCLE, but there is some
relation, i should think. I am not a physicist, but i think having two well-aligned gyroscopes
operating in the same planes but different tracks is gonna cause different harmonics than a simply
out-of-true wheel. When someone moves them into different planes by 'correcting' the out-of-dish
wheel between the brake shoes, a DIFFERENT set of harmonics should appear - i think. Again, two
gyroscope, this time on different axes. Anyway, I'm gonna do some formal experiments with this and
will report back - Ъ×