speed wobbles

1--- check frame alignment

(Brian Schlachta) said:

Friend of mine has a Colnago Master X-Lite. It's a sweet looking machine even tho it has
Dura-Ace on. Prob is is that he gets a wobble at around 65 km/h when in the drops, and
around 70 km/h with his hands in the tops. I seem to remember reading something about rider
weight, top tube flexibility and rider position as possible causes of a wobble and that it
can (sometimes) be fixed by altering ones setup on the bike. Any ideas, or does he have a
nice looking cuiser.

tkx, Brian

Quoting from a faq at draco.acs.uci.edu8h.5.htmlOpen ↗ (a great URL/URI that you should
bookmark):

I will just add that besides taking the weicht off the fulcrum (saddle), the spped wobble can be
stopped by clamping the top tube between the knees - one is usually spun out descending when the
phenomenon manifests itself.

Subject: 8h.5 Shimmy or Speed Wobble From: Jobst Brandt <[email hidden]>

Shimmy is not related to frame alignment or loose bearings as is often suggested. Shimmy arises from
the dynamics of forward motion and the elasticity of the frame, fork, and wheels, and the saddle
position. Both perfectly aligned bicycles and ones with wheels out of plane to one another shimmy
nearly equally well. The same is true for bearing adjustment. In fact shimmy is more likely with
properly adjusted bearings than loose ones. The bearing or alignment concept is usually offered as a
cause of shimmy and each airing perpetuates the idea.

Shimmy, the lateral oscillation at the head tube, depends primarily on the frame and its geometry.
The inflation of the tire and the gyroscopic effects of the front wheel make it largely speed
dependent. It cannot be fixed by adjustments because it is inherent to the geometry and elasticity
of the components. The longer the frame and the higher the saddle, the greater the tendency to
shimmy, other things being equal. Weight distribution also has no effect on shimmy although where
that weight contacts the frame does.

In contrast to common knowledge, a well aligned frame shimmies more easily than a crooked one
because it rides straight and without bias. The bias force of a crooked frame impedes shimmy
slightly. Because many riders never ride no-hands downhill, or at least not in the critical speed
range, they seldom encounter shimmy. When it occurs with the hands on the bars it is unusual and
especially disconcerting. There is a preferred speed at which shimmy initiates when coasting
no-hands on a smooth road and it should occur every time when in that critical speed range. Although
it usually does not initiate at higher speed, it can.

Pedaling or rough road interferes with shimmy on a bicycle that isn't highly susceptible. When
coasting, laying one leg against the top tube is the most common way to inhibit it. Interestingly,
compliant tread of knobby tires give such high lateral damping that most bicycles equipped with
knobbies do not shimmy.

Shimmy is caused by the gyroscopic force of the front wheel that acts at 90 degrees to the axis of
the steering motion. The wheel steers to the left about a vertical axis when it is leaned to the
left about a horizontal axis. When the wheel leans to the one side, gyroscopic force steers it
toward that side, however, the steering action immediately reverses the lean of the wheel as the
tire contact point acts on the trail of the fork caster to reverse the steering motion.

The shimmy oscillates at a rate that the rider's mass on the saddle cannot follow, causing the top
and down tubes to act as springs that store the energy that initiates the return swing. The shimmy
will stop if the rider unloads the saddle, because the mass of the rider is the anchor about which
the oscillation operates. Without this anchor no energy is stored. The fork and wheels may store
some energy, although it appears the frame acts as the principal spring.

Shimmy can also be initiated with the hands firmly on the bars by shivering, typically in cold
weather. The frequency of human shivering is about the same as that of a typical bicycle frame.

--
le vent a Dos

Davey Crockett

Excellent reply. Thank you!

"Davey crockett" <[email hidden]> wrote in message
"]news:[email hidden]. ..

Quoted message said:

(Brian Schlachta) said:

Friend of mine has a Colnago Master X-Lite. It's a sweet looking
machine even tho it has Dura-Ace on. Prob is is that he gets a wobble at
around 65 km/h when in the drops, and around 70 km/h with his hands in

the

Quoted message said:

Quoted message said:

tops. I seem to remember reading something about rider weight, top tube flexibility and rider
position as possible causes of a wobble and that

it

Quoted message said:

Quoted message said:

can (sometimes) be fixed by altering ones setup on the bike. Any ideas,

or

Quoted message said:

Quoted message said:

does he have a nice looking cuiser.

tkx, Brian

Quoting from a faq at draco.acs.uci.edu8h.5.htmlOpen ↗ (a great URL/URI that you
should bookmark):

I will just add that besides taking the weicht off the fulcrum (saddle), the spped wobble can be
stopped by clamping the top tube between the knees - one is usually spun out descending when the
phenomenon manifests itself.

Subject: 8h.5 Shimmy or Speed Wobble From: Jobst Brandt <[email hidden]>

Shimmy is not related to frame alignment or loose bearings as is often suggested. Shimmy arises
from the dynamics of forward motion and the elasticity of the frame, fork, and wheels, and the
saddle position. Both perfectly aligned bicycles and ones with wheels out of plane to one another
shimmy nearly equally well. The same is true for bearing adjustment. In fact shimmy is more likely
with properly adjusted bearings than loose ones. The bearing or alignment concept is usually
offered as a cause of shimmy and each airing perpetuates the idea.

Shimmy, the lateral oscillation at the head tube, depends primarily on the frame and its geometry.
The inflation of the tire and the gyroscopic effects of the front wheel make it largely speed
dependent. It cannot be fixed by adjustments because it is inherent to the geometry and elasticity
of the components. The longer the frame and the higher the saddle, the greater the tendency to
shimmy, other things being equal. Weight distribution also has no effect on shimmy although where
that weight contacts the frame does.

In contrast to common knowledge, a well aligned frame shimmies more easily than a crooked one
because it rides straight and without bias. The bias force of a crooked frame impedes shimmy
slightly. Because many riders never ride no-hands downhill, or at least not in the critical speed
range, they seldom encounter shimmy. When it occurs with the hands on the bars it is unusual and
especially disconcerting. There is a preferred speed at which shimmy initiates when coasting
no-hands on a smooth road and it should occur every time when in that critical speed range.
Although it usually does not initiate at higher speed, it can.

Pedaling or rough road interferes with shimmy on a bicycle that isn't highly susceptible. When
coasting, laying one leg against the top tube is the most common way to inhibit it. Interestingly,
compliant tread of knobby tires give such high lateral damping that most bicycles equipped with
knobbies do not shimmy.

Shimmy is caused by the gyroscopic force of the front wheel that acts at 90 degrees to the axis of
the steering motion. The wheel steers to the left about a vertical axis when it is leaned to the
left about a horizontal axis. When the wheel leans to the one side, gyroscopic force steers it
toward that side, however, the steering action immediately reverses the lean of the wheel as the
tire contact point acts on the trail of the fork caster to reverse the steering motion.

The shimmy oscillates at a rate that the rider's mass on the saddle cannot follow, causing the top
and down tubes to act as springs that store the energy that initiates the return swing. The shimmy
will stop if the rider unloads the saddle, because the mass of the rider is the anchor about which
the oscillation operates. Without this anchor no energy is stored. The fork and wheels may store
some energy, although it appears the frame acts as the principal spring.

Shimmy can also be initiated with the hands firmly on the bars by shivering, typically in cold
weather. The frequency of human shivering is about the same as that of a typical bicycle frame.

--
le vent a Dos

Davey Crockett

Davey crockett <[email hidden]> wrote in
"]news:[email hidden] om:

Quoted message said:

(Brian Schlachta) said:

Friend of mine has a Colnago Master X-Lite. It's a sweet looking machine even tho it has
Dura-Ace on. Prob is is that he gets a wobble at around 65 km/h when in the drops, and
around 70 km/h with his hands in the tops. I seem to remember reading something about
rider weight, top tube flexibility and rider position as possible causes of a wobble and
that it can (sometimes) be fixed by altering ones setup on the bike. Any ideas, or does
he have a nice looking cuiser.

tkx, Brian

Quoting from a faq at draco.acs.uci.edu8h.5.htmlOpen ↗ (a great URL/URI that you
should bookmark):

I will just add that besides taking the weicht off the fulcrum (saddle), the spped wobble can be
stopped by clamping the top tube between the knees - one is usually spun out descending when the
phenomenon manifests itself.

Subject: 8h.5 Shimmy or Speed Wobble From: Jobst Brandt <[email hidden]>

Shimmy is not related to frame alignment or loose bearings as is often suggested. Shimmy arises
from the dynamics of forward motion and the elasticity of the frame, fork, and wheels, and the
saddle position. Both perfectly aligned bicycles and ones with wheels out of plane to one another
shimmy nearly equally well. The same is true for bearing adjustment. In fact shimmy is more likely
with properly adjusted bearings than loose ones. The bearing or alignment concept is usually
offered as a cause of shimmy and each airing perpetuates the idea.

Shimmy, the lateral oscillation at the head tube, depends primarily on the frame and its geometry.
The inflation of the tire and the gyroscopic effects of the front wheel make it largely speed
dependent. It cannot be fixed by adjustments because it is inherent to the geometry and elasticity
of the components. The longer the frame and the higher the saddle, the greater the tendency to
shimmy, other things being equal. Weight distribution also has no effect on shimmy although where
that weight contacts the frame does.

In contrast to common knowledge, a well aligned frame shimmies more easily than a crooked one
because it rides straight and without bias. The bias force of a crooked frame impedes shimmy
slightly. Because many riders never ride no-hands downhill, or at least not in the critical speed
range, they seldom encounter shimmy. When it occurs with the hands on the bars it is unusual and
especially disconcerting. There is a preferred speed at which shimmy initiates when coasting
no-hands on a smooth road and it should occur every time when in that critical speed range.
Although it usually does not initiate at higher speed, it can.

Pedaling or rough road interferes with shimmy on a bicycle that isn't highly susceptible. When
coasting, laying one leg against the top tube is the most common way to inhibit it. Interestingly,
compliant tread of knobby tires give such high lateral damping that most bicycles equipped with
knobbies do not shimmy.

Shimmy is caused by the gyroscopic force of the front wheel that acts at 90 degrees to the axis of
the steering motion. The wheel steers to the left about a vertical axis when it is leaned to the
left about a horizontal axis. When the wheel leans to the one side, gyroscopic force steers it
toward that side, however, the steering action immediately reverses the lean of the wheel as the
tire contact point acts on the trail of the fork caster to reverse the steering motion.

The shimmy oscillates at a rate that the rider's mass on the saddle cannot follow, causing the top
and down tubes to act as springs that store the energy that initiates the return swing. The shimmy
will stop if the rider unloads the saddle, because the mass of the rider is the anchor about which
the oscillation operates. Without this anchor no energy is stored. The fork and wheels may store
some energy, although it appears the frame acts as the principal spring.

Shimmy can also be initiated with the hands firmly on the bars by shivering, typically in cold
weather. The frequency of human shivering is about the same as that of a typical bicycle frame.

Tkx, I'll send him the info. Hopefully, he''l be able to find a solution. It's [censored] him
off a bit. Paying top $ for such a nice bike and having it go all silly on him is pretty
aggrivating.

Brian

"Aarron Canino" <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Excellent reply. Thank you!

No problem, Tuba-boy!

Deez

try some cheap traditional wheels with 25's on the front, and I'll doubt if you have a shimmy.

Brian Schlachta said:

Tkx, I'll send him the info. Hopefully, he''l be able to find a solution. It's [censored] him off
a bit. Paying top $ for such a nice bike and having it go all silly on him is pretty
aggrivating.

The solution is spelled out quite explicitly in Jobst's explanation. I certainly hope your friend
can find it.

Aarron Canino said:

Learn how to follow a thread, dipshit. The thank you was not aimed at you.

Welcome back Mr. Canino. You are as in as fine a style as ever.

Dizzle is is trying to say how much he has missed you.

groups.google.comgroupsOpen ↗
le.com groups.google.comgroupsOpen ↗
ng.google.com

Quoted message said:

"Deeznuts" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Aarron Canino" <[email hidden]> wrote in message

news:<[email hidden]>...

Quoted message said:

Quoted message said:

Excellent reply. Thank you!

No problem, Tuba-boy!

Deez

Wow! I didn't know that Deeznuts cared so much! What does that say about him that his life is so
incomplete without someone for whom he has so little respect and whom he would consider to be a
loser in his narrow-mided view of the world? Sad to see that in his own special, ignorant way, Deez
has proclaimed to the group that he is so far lower than me in this world.

By the way, Deez, if you are reading this, if you are that bored and lonely without me around, I am
sure you are proficient enough with Google that you could probably locate a picture of me somewhere
that, if you can find your [censored], you could probably masturbate to during those lonely nights when
even good [censored] can't make it happen for you.

"gwhite" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

Aarron Canino said:

Learn how to follow a thread, dipshit. The thank you was not aimed at

you.

Quoted message said:

Welcome back Mr. Canino. You are as in as fine a style as ever.

Dizzle is is trying to say how much he has missed you.

groups.google.comgroupsOpen ↗.
3f272b3d%40posting.google.com

Quoted message said:

groups.google.comgroupsOpen ↗.
39abf64b%40posting.google.com

Quoted message said:

Quoted message said:

"Deeznuts" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

"Aarron Canino" <[email hidden]> wrote in message

news:<[email hidden]>...

Quoted message said:

> Excellent reply. Thank you!

No problem, Tuba-boy!

Deez

What would 25mm tires do to help prevent the shimmy? Cheap traditional wheels? Lanny "Callistus
Valerius" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

try some cheap traditional wheels with 25's on the front, and I'll doubt

if

Quoted message said:

you have a shimmy.

"Kyle Legate" <[email hidden]> wrote in
:"]news:[email hidden]:

Quoted message said:

Brian Schlachta said:

Tkx, I'll send him the info. Hopefully, he''l be able to find a solution. It's [censored] him off
a bit. Paying top $ for such a nice bike and having it go all silly on him is pretty
aggrivating.

The solution is spelled out quite explicitly in Jobst's explanation. I certainly hope your friend
can find it.

hehe, I hope so to. I think he's getting a print-out of it tonight. We'll see what
happens. If he ends up in the ditch with a wrecked bike I sure ain't taking responsibility
for it lol.

later, Brian

"Lanny R. Levenson" <[email hidden]> wrote in message
"]news:[email hidden]...

Quoted message said:

What would 25mm tires do to help prevent the shimmy? Cheap traditional wheels? Lanny "Callistus
Valerius" <[email hidden]> wrote in message "]news:[email hidden]...

Quoted message said:

try some cheap traditional wheels with 25's on the front, and I'll doubt

if

Quoted message said:

you have a shimmy.

Your expensive bike will be so self-conscious of the cheap wheels and big tyres, it will refuse to
shimmy, thereby not drawing attention to its embarrassing problem.

Or maybe the heavier wheel and tyre will increase the stabilizing gyroscopic effect, thereby
decreasing the lateral oscillation? But what the hell to I know about shimmy and lateral
oscillation?

Vol

"Aarron Canino" <[email hidden]> wrote in message
news:<[email hidden]>...

Quoted message said:

Wow! I didn't know that Deeznuts cared so much! What does that say about him that his life is so
incomplete without someone for whom he has so little respect and whom he would consider to be a
loser in his narrow-mided view of the world? Sad to see that in his own special, ignorant way,
Deez has proclaimed to the group that he is so far lower than me in this world.

Aarroon,

It's good to have your fat ass back, man. This NG has really sucked without your Tuba-playing
expertise. I know you are pretty busy between your job at the mall and pimping on all of your
Tuba-groupies, but we need your presence here.

Quoted message said:

By the way, Deez, if you are reading this, if you are that bored and lonely without me around, I
am sure you are proficient enough with Google that you could probably locate a picture of me
somewhere that, if you can find your [censored], you could probably masturbate to during those lonely
nights when even good [censored] can't make it happen for you.

I did see a picture of you once. I have been trying to forget it ever since.

Deez