New Bike, Couple of Quirks

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Date: 15 Oct 2006 22:22:13
From:
Subject: New Bike, Couple of Quirks

I've been threatening to do this for some time, and finally carried the
threat out. After several years riding almost exclusively on a
tough-but-heavy MTB, I bought myself a road bike. My new steed is a
Specialized Allez, aluminum frame with carbon fiber forks--far from the
top of the line, but not down at the bottom either. It took some doing to
find a frame size large enough for me (62 cm), but the hunt was worth it.
The bike fits me well.
The first free weekend I had after the purchase, I took the bike out
for a long ride. I covered 69 miles in around five hours, a much better
pace than I've ever managed on my MTB, and one that bodes well for my goal
of riding at least 75 in next year's MS 150.
Three problems I've noticed with the new bike. One is serious TB after
about the 40th mile. I suppose that tinkering with the seat will take
care of that. I'm also just getting used to the new-fangled brake-lever
shifters. (I figured out how those work the first time I saw a set in a
shop, but I don't fault anyone who is mystified by them at first.) I kind
of wonder about my front shifter, though. Sometimes when I shift up from
the small chain ring to the middle, it feels like the chain hasn't lined
up quite right. And a couple of times when I've shifted up to the large
chain ring, the chain has kept right on going. Fortunately, both times
the peg between the sprocket and the crank arm has brought it back to
where it got back on the teeth, but I sure hope that never happens to me
in a tight spot.
The problem that really has me baffled appears when I get the bike
above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
starts to shimmy, with the greatest motion apparent in the head tube,
which vibrates back and forth an inch or a little bit more at about two or
three oscillations per second. It's not a problem as long as I keep a
firm grip on the handlebars, but still it doesn't seem like that should be
happening. It never did on my old Astra.
As soon as I get a couple hundred more miles on the bike I'm scheduled
to take it back to the shop for a fine tuning. Is there anything I could
be doing myself in the meantime for these problems? Is there something I
should be asking the LBS folks to do?

Bill in Utah

------------------------------------------------

Date: 17 Oct 2006 20:55:13
From: BobT
Subject: Re: New Bike, Couple of Quirks

<D_Frumious_B@ndersnat.ch > wrote in message
news:egucal$rla$1@news.xmission.com...
> The problem that really has me baffled appears when I get the bike
> above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
> starts to shimmy, with the greatest motion apparent in the head tube,
> which vibrates back and forth an inch or a little bit more at about two or
> three oscillations per second. It's not a problem as long as I keep a
> firm grip on the handlebars, but still it doesn't seem like that should be
> happening. It never did on my old Astra.
> As soon as I get a couple hundred more miles on the bike I'm scheduled
> to take it back to the shop for a fine tuning. Is there anything I could
> be doing myself in the meantime for these problems? Is there something I
> should be asking the LBS folks to do?
>
>
> Bill in Utah

I wouldn't accept a new bike that has shimmy. A brief search of this
newgroup
or elsewhere will yield a lot of info on this problem. If your bike is new,
I would take it back to the point of purchase, complain about the shimmy,
and demand a refund and buy another bike that doesn't have this problem.

I had an old bike that has incredibly frightening shimmy that only developed
with hands off at high speeds - descending above 30 mph. It never caused
me to crash but it was extremely hair raising at times. When I begin riding
more in the mountains where high speed descents became common, I
replaced it.

BobT

Date: 20 Oct 2006 08:52:49
From: David L. Johnson
Subject: Re: Shimmy

On Thu, 19 Oct 2006 23:06:54 -0500, BobT wrote:

> This is an interesting point. If I am thinking about this right, I could
> get
> a shorter stem, a lighter and/or narrower bar, get rid of my STI brifters
> and put on much lighter brake only levers and put the shift levers on the
> down tube - all of these things would lower the moment of inertia of
> the handlebars.
>
> In this type of shimmy, is the moment of inertia of the bar assembly
> (stem, bar, any accessories) significant relative to fork and rotating
> wheel?

What is significant or not is basically unknowable. There are so many
factors that can contribute to "tuning" the system -- bike and rider -- to
achieve shimmy at a given speed in a given situation, that you cannot
pinpoint a specific cause.

This enables many "experts", who claim it _has_ to be one particular
thing, such as an over-tight or over-loose headset, or some imagined
feature of the stem --- because once they changed that thing, the system
no longer responded with the shimmy in the situation they found annoying.

Change something, anything you have been wanting to change for some other
reason. It might be enough to stop your shimmy problems, and at least you
will be happier about the bike. But if you are going to give up perfectly
usable shifter/brake levers, send them to me.

--

David L. Johnson

__o

Date: 20 Oct 2006 19:23:45
From:
Subject: Re: Shimmy

David L. Johnson writes:

>> This is an interesting point. If I am thinking about this right, I
>> could get a shorter stem, a lighter and/or narrower bar, get rid of
>> my STI brifters and put on much lighter brake only levers and put
>> the shift levers on the down tube - all of these things would lower
>> the moment of inertia of the handlebars.

>> In this type of shimmy, is the moment of inertia of the bar
>> assembly (stem, bar, any accessories) significant relative to fork
>> and rotating wheel?

> What is significant or not is basically unknowable. There are so
> many factors that can contribute to "tuning" the system -- bike and
> rider -- to achieve shimmy at a given speed in a given situation,
> that you cannot pinpoint a specific cause.

> This enables many "experts", who claim it _has_ to be one particular
> thing, such as an over-tight or over-loose headset, or some imagined
> feature of the stem --- because once they changed that thing, the
> system no longer responded with the shimmy in the situation they
> found annoying.

> Change something, anything you have been wanting to change for some
> other reason. It might be enough to stop your shimmy problems, and
> at least you will be happier about the bike. But if you are going
> to give up perfectly usable shifter/brake levers, send them to me.

Add to that the experiment of filling the front tire with water
instead of air that had no perceptible effect on shimmy. That came
before the definitive test of a Rolf Vector Pro, a standard 36-spoke,
and a Bontrager paired spoke wheel to assess shimmy tendencies. None
of the above had any effect on shimmy.

Jobst Brandt

Date: 19 Oct 2006 16:20:55
From: Michael Warner
Subject: Re: New Bike, Couple of Quirks

On Tue, 17 Oct 2006 20:55:13 -0500, BobT wrote:

> I wouldn't accept a new bike that has shimmy.

It's not necessarily the bike. A friend of mine bought a new bike - carbon
rather than alloy frame, and twitchier - and shimmied badly on it. Same
with another carbon bike he tried (Giant TCR and Bianchi, FWIW).

Once he got used to the different feel of the TCR, the problem went away.
I think he was holding the bars too tight, and not relaxing enough.

--
Home page: http://members.westnet.com.au/mvw

Date: 18 Oct 2006 17:25:53
From: Mike Jacoubowsky
Subject: Re: New Bike, Couple of Quirks

> I wouldn't accept a new bike that has shimmy. A brief search of this
> newgroup
> or elsewhere will yield a lot of info on this problem. If your bike is
> new,
> I would take it back to the point of purchase, complain about the shimmy,
> and demand a refund and buy another bike that doesn't have this problem.

That sort of attitude might not solve any problems, as it ignores the fact
that many shimmy issues are caused by riders who haven't yet adapted to a
bike that handles differently than what they rode before. And since rider
confidence (or lack thereof) is a major cause of instability on a bike,
telling someone to take a bike back to the shop because it has to be
fixed... for something that may not be a problem with the bike at all...
will simply create a downward spiral in confidence about cycling.

Especially on larger frames, it's impossible to design a (high performance)
bike that cannot shimmy under certain circumstances, and yet is still
responsive enough to make you want to ride it. Sure, you can go to a very
long wheelbase, add a fairly slack head tube and an appropriately-long fork
offset and have something that you could fall asleep on a fast descent and
still make it to the bottom of the hill. But that's probably not the type of
bike we're talking about.

We've sold many, many thousands of road bikes over the years. And we've had
a small handful (very small, thankfully) who are experts at getting a given
bike to shimmy for them, while nobody else does. In nearly every case it's
something about the way they ride. Sometimes a death-grip on the bars,
sometimes they want to ride no-hand in a cross-wind, sometimes they're just
positioned a bit oddly on the bike fore/aft. Most of us almost instantly
adapt to a bicycle's handling characteristics in a way that eliminates or
minimizes shimmy.

My first carbon road bike, a 1992 Trek 5200, developed a "death wobble" on
its very first ride (a century in the Monterey area, and the shimmy happened
on a high-speed descent on the north side of Los Laureles Grade). I'd never
felt anything like it... thought there was something wrong with the bike. I
stopped completely, checked things out, collected my wits and set out again.
The shimmy never happened again. Undoubtedly I adapted my position and
riding style ever-so-slightly without thinking about it. Normally this would
probably happen before it ever got to that point, but when you build up a
bike the night before its first ride, and the first ride is a century...

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

"BobT" <robertleetaylorRe@MoveThisCox.net > wrote in message
news:xNfZg.330$uF.51@dukeread12...
> <D_Frumious_B@ndersnat.ch> wrote in message
> news:egucal$rla$1@news.xmission.com...
>> The problem that really has me baffled appears when I get the bike
>> above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
>> starts to shimmy, with the greatest motion apparent in the head tube,
>> which vibrates back and forth an inch or a little bit more at about two
>> or
>> three oscillations per second. It's not a problem as long as I keep a
>> firm grip on the handlebars, but still it doesn't seem like that should
>> be
>> happening. It never did on my old Astra.
>> As soon as I get a couple hundred more miles on the bike I'm scheduled
>> to take it back to the shop for a fine tuning. Is there anything I could
>> be doing myself in the meantime for these problems? Is there something I
>> should be asking the LBS folks to do?
>>
>>
>> Bill in Utah
>
> I wouldn't accept a new bike that has shimmy. A brief search of this
> newgroup
> or elsewhere will yield a lot of info on this problem. If your bike is
> new,
> I would take it back to the point of purchase, complain about the shimmy,
> and demand a refund and buy another bike that doesn't have this problem.
>
> I had an old bike that has incredibly frightening shimmy that only
> developed
> with hands off at high speeds - descending above 30 mph. It never caused
> me to crash but it was extremely hair raising at times. When I begin
> riding
> more in the mountains where high speed descents became common, I
> replaced it.
>
> BobT
>
>

Date: 19 Oct 2006 17:45:50
From: BobT
Subject: Re: New Bike, Couple of Quirks

"Mike Jacoubowsky" <mikej1@ix.netcom.com > wrote in message
news:BstZg.20918$7I1.19039@newssvr27.news.prodigy.net...
> That sort of attitude might not solve any problems, as it ignores the fact
> that many shimmy issues are caused by riders who haven't yet adapted to a
> bike that handles differently than what they rode before. And since rider
> confidence (or lack thereof) is a major cause of instability on a bike,
> telling someone to take a bike back to the shop because it has to be
> fixed... for something that may not be a problem with the bike at all...
> will simply create a downward spiral in confidence about cycling.
>
> --Mike-- Chain Reaction Bicycles
> www.ChainReactionBicycles.com

Your suggestions are not persuasive to me.

Bill in Utah doesn't seem to be describing a difficult to produce shimmy.
Hands-on shimmy may be caused by "rider confidence (or lack thereof)" as
you note. But Bill says he simply took his hands off the bars while riding
faster than 20 mph and the bike begin to shimmy.

My "attitude" and suggestion would indeed solve a problem for Bill.
He wouldn't be stuck with a brand new bike that he might not want.
Of that creates a problem for the bike seller with whom I also have
sympathy.

For me, he described an unacceptable bike problem. I want to sometimes be
able to take my hands off the bars for a few seconds. I lived with this
problem for several years on bike I bought in 1991 but it only shimmied
when I was going really fast with hands completely off the bars. If this
problem occurs at common riding speeds like 20 mph, I don't think I
could live with that. Of course this is an individual decision and you
might feel differently. I realize that one might be able to weight or
unweight the saddle or pedals just right or squeeze the top tube with
legs just right and avoid the shimmy but I think that is a lot to ask when
someone just bought a brand new relatively expensive bike shop bike.

BobT

Date: 19 Oct 2006 23:37:38
From: Mike Jacoubowsky
Subject: Re: New Bike, Couple of Quirks

> Your suggestions are not persuasive to me.
>
> Bill in Utah doesn't seem to be describing a difficult to produce shimmy.
> Hands-on shimmy may be caused by "rider confidence (or lack thereof)" as
> you note. But Bill says he simply took his hands off the bars while
> riding
> faster than 20 mph and the bike begin to shimmy.

He also has an issue with "TB" (an abbreviation I can't quite figure out)
that he thinks has something to do with his position on the bike. If he's
got a nose-down seat position, that could be the cause of his shimmy, as his
weight shifts forward and, without his hands to maintain position, he's in a
very awkward state on the bike.

> My "attitude" and suggestion would indeed solve a problem for Bill.
> He wouldn't be stuck with a brand new bike that he might not want.
> Of that creates a problem for the bike seller with whom I also have
> sympathy.

The only problem that's guaranteed to fix is removing him from a bike
entirely. All things being equal, he could end up on a different bike with
the same result. We should be looking at the cause of the problem, and
recognize that a bicycle on the road is a combination of rider+bike. Unlike
driving a car, a bike cannot stay upright without a moderate amount of skill
(easily learned by most of us). Don't get me wrong; I'm not "blaming" the
user, but it's quite likely that minor modifications will make his world a
much better place.

> For me, he described an unacceptable bike problem. I want to sometimes be
> able to take my hands off the bars for a few seconds. I lived with this
> problem for several years on bike I bought in 1991 but it only shimmied
> when I was going really fast with hands completely off the bars. If this
> problem occurs at common riding speeds like 20 mph, I don't think I
> could live with that. Of course this is an individual decision and you
> might feel differently. I realize that one might be able to weight or
> unweight the saddle or pedals just right or squeeze the top tube with
> legs just right and avoid the shimmy but I think that is a lot to ask when
> someone just bought a brand new relatively expensive bike shop bike.
>
> BobT

--
--Mike Jacoubowsky
Chain Reaction Bicycles
www.ChainReaction.com
Redwood City & Los Altos, CA USA
"BobT" <robertleetaylorRe@MoveThisCox.net > wrote in message
news:_bTZg.398$uF.357@dukeread12...
> "Mike Jacoubowsky" <mikej1@ix.netcom.com> wrote in message
> news:BstZg.20918$7I1.19039@newssvr27.news.prodigy.net...
>> That sort of attitude might not solve any problems, as it ignores the
>> fact that many shimmy issues are caused by riders who haven't yet adapted
>> to a bike that handles differently than what they rode before. And since
>> rider confidence (or lack thereof) is a major cause of instability on a
>> bike, telling someone to take a bike back to the shop because it has to
>> be fixed... for something that may not be a problem with the bike at
>> all... will simply create a downward spiral in confidence about cycling.
>>
>> --Mike-- Chain Reaction Bicycles
>> www.ChainReactionBicycles.com
>
> Your suggestions are not persuasive to me.
>
> Bill in Utah doesn't seem to be describing a difficult to produce shimmy.
> Hands-on shimmy may be caused by "rider confidence (or lack thereof)" as
> you note. But Bill says he simply took his hands off the bars while
> riding
> faster than 20 mph and the bike begin to shimmy.
>
> My "attitude" and suggestion would indeed solve a problem for Bill.
> He wouldn't be stuck with a brand new bike that he might not want.
> Of that creates a problem for the bike seller with whom I also have
> sympathy.
>
> For me, he described an unacceptable bike problem. I want to sometimes be
> able to take my hands off the bars for a few seconds. I lived with this
> problem for several years on bike I bought in 1991 but it only shimmied
> when I was going really fast with hands completely off the bars. If this
> problem occurs at common riding speeds like 20 mph, I don't think I
> could live with that. Of course this is an individual decision and you
> might feel differently. I realize that one might be able to weight or
> unweight the saddle or pedals just right or squeeze the top tube with
> legs just right and avoid the shimmy but I think that is a lot to ask when
> someone just bought a brand new relatively expensive bike shop bike.
>
> BobT
>
>

Date: 16 Oct 2006 19:41:29
From: amakyonin
Subject: Re: New Bike, Couple of Quirks

catzz66 wrote:
> amakyonin wrote:
> >
> > I have 58cm 03 Allez elite which is essentially the same geometry. It
> > shimmied for me with the hands on the handlebars only once the first
> > time after I took it down a long steep hill. This may just have been
> > exacerbated by me being overly tense because of unfamiliarity with the
> > bike. I would also get a consistent shimmy with hands-off at about the
> > 20mph point as well. This was eliminated when I lowered the handlebars
> > (two settings from the top of the four position stem)
> >
>
> This may be a dumb question, but does that effectively just put more
> weight on the front wheel? Mine is an Elite, too.

With hands-off? not really. With hands-on. Yes, but only slightly. I
think the biggest factor is just the redistribution of the mass of the
handlebars+accoutrements. Note that I could also diminish the shimmy
and reduce its frequency by mounting an empty bar bag (~4 lbs). This
acted as a like a damping counterweight positioned halfway out in front
of the hooks. The no hands shimmy also seemed to disappear with a
loaded bar bag but I couldn't really test it much because of the
tendency to flop around with so much weight up and ahead of the bars.

Date: 16 Oct 2006 21:50:58
From: Chris Y.F.N.W.
Subject: Re: New Bike, Couple of Quirks

A certain jinxian equatorial swamp-dweller wrote: <edited >

>Three problems I've noticed with the
>new bike. One is serious TB after about
>the 40th mile. I suppose that tinkering
>with the seat will take care of that.

Saddle fit is a tricky and personal business. If tinkering with the
position doesn't help, try other saddles, take note as to what hurts and
use your well tuned bike sense to determine what's causing it (too
narrow? too wide? needs fart hole? etc.) and look for models that will
address these issues. It took me a couple of years after I started
cycling seriously to find a saddle that satisfied my bum (a Brooks B17,
if you're curious).

>I kind of wonder about my front shifter,
>though. Sometimes when I shift up from
>the small chain ring to the middle, it
>feels like the chain hasn't lined up quite
>right. And a couple of times when I've
>shifted up to the large chain ring, the
>chain has kept right on going.

>Fortunately, both times the peg between
>the sprocket and the crank arm has
>brought it back to where it got back on
>the teeth, but I sure hope that never
>happens to me in a tight spot.

The adjustment on brifters has to be just right, esp. with super narrow
chains as those used on nine and above speeds, as the cage is narrower
as well. If you can, try to find a front brifter that allows for fine
tuning IOW, it has more clicks than the minimum required for the number
of sprockets. in your case, more that three lever positions. I think
sone of the Campy front brifters have intermediate clicks.

Or you can abandon the front brifter altogether and go for a friction
bar-con shifter, which allows for fine tuning of the front Mech. When I
took off my brifters and went back to bar-cons, all my front shift
problems, which were the same as you described disappeared, and haven't
been heard from since.

>The problem that really has me baffled
>appears when I get the bike above 20 >mph. Loosen my grip on the
handlebars,
>or let go, and the bike starts to shimmy,
>with the greatest motion apparent in the
>head tube, which vibrates back and forth
>an inch or a little bit more at about two
>or three oscillations per second.

>As soon as I get a couple hundred
>more miles on the bike I'm scheduled to
>take it back to the shop for a fine tuning.
>Is there anything I could be doing myself
>in the meantime for these problems? Is
>there something I should be asking the
>LBS folks to do?

>Bill in Utah

Tell them about the shimmy problem and describe it as you did here.
Front wheel shimmy can be caused by many things (or a combination of).
Frame alignment, wheel alignment, trueness, loose spokes, the list goes
on.

- -
Compliments of:
"Your Friendly Neighborhood Wheelman"

If you want to E-mail me use:
ChrisZCorner "at" webtv "dot" net

My website:
http://geocities.com/czcorner

Date: 16 Oct 2006 13:12:58
From: amakyonin
Subject: Re: New Bike, Couple of Quirks

D_Frumious_B@ndersnat.ch wrote:
> The problem that really has me baffled appears when I get the bike
> above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
> starts to shimmy, with the greatest motion apparent in the head tube,
> which vibrates back and forth an inch or a little bit more at about two or
> three oscillations per second. It's not a problem as long as I keep a
> firm grip on the handlebars, but still it doesn't seem like that should be
> happening. It never did on my old Astra.
>
> Bill in Utah

I have 58cm 03 Allez elite which is essentially the same geometry. It
shimmied for me with the hands on the handlebars only once the first
time after I took it down a long steep hill. This may just have been
exacerbated by me being overly tense because of unfamiliarity with the
bike. I would also get a consistent shimmy with hands-off at about the
20mph point as well. This was eliminated when I lowered the handlebars
(two settings from the top of the four position stem)

Date: 16 Oct 2006 15:52:10
From: catzz66
Subject: Re: New Bike, Couple of Quirks

amakyonin wrote:
>
> I have 58cm 03 Allez elite which is essentially the same geometry. It
> shimmied for me with the hands on the handlebars only once the first
> time after I took it down a long steep hill. This may just have been
> exacerbated by me being overly tense because of unfamiliarity with the
> bike. I would also get a consistent shimmy with hands-off at about the
> 20mph point as well. This was eliminated when I lowered the handlebars
> (two settings from the top of the four position stem)
>

This may be a dumb question, but does that effectively just put more
weight on the front wheel? Mine is an Elite, too.

Date: 16 Oct 2006 09:57:44
From: catzz66
Subject: Re: New Bike, Couple of Quirks

There are several different Allez models, but the fork angle on mine is
different from my other bike. The Allez fork is more vertical, making
the Allez a little more twitchy (or responsive, if you look at it the
other way) than my old bike. I don't feel any shimmy, but never ride
without at least one hand on the bars.

D_Frumious_B@ndersnat.ch wrote:
> I've been threatening to do this for some time, and finally carried the
> threat out. After several years riding almost exclusively on a
> tough-but-heavy MTB, I bought myself a road bike. My new steed is a
> Specialized Allez, aluminum frame with carbon fiber forks--far from the
> top of the line, but not down at the bottom either. It took some doing to
> find a frame size large enough for me (62 cm), but the hunt was worth it.
> The bike fits me well.
> The first free weekend I had after the purchase, I took the bike out
> for a long ride. I covered 69 miles in around five hours, a much better
> pace than I've ever managed on my MTB, and one that bodes well for my goal
> of riding at least 75 in next year's MS 150.
> Three problems I've noticed with the new bike. One is serious TB after
> about the 40th mile. I suppose that tinkering with the seat will take
> care of that. I'm also just getting used to the new-fangled brake-lever
> shifters. (I figured out how those work the first time I saw a set in a
> shop, but I don't fault anyone who is mystified by them at first.) I kind
> of wonder about my front shifter, though. Sometimes when I shift up from
> the small chain ring to the middle, it feels like the chain hasn't lined
> up quite right. And a couple of times when I've shifted up to the large
> chain ring, the chain has kept right on going. Fortunately, both times
> the peg between the sprocket and the crank arm has brought it back to
> where it got back on the teeth, but I sure hope that never happens to me
> in a tight spot.
> The problem that really has me baffled appears when I get the bike
> above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
> starts to shimmy, with the greatest motion apparent in the head tube,
> which vibrates back and forth an inch or a little bit more at about two or
> three oscillations per second. It's not a problem as long as I keep a
> firm grip on the handlebars, but still it doesn't seem like that should be
> happening. It never did on my old Astra.
> As soon as I get a couple hundred more miles on the bike I'm scheduled
> to take it back to the shop for a fine tuning. Is there anything I could
> be doing myself in the meantime for these problems? Is there something I
> should be asking the LBS folks to do?
>
>
> Bill in Utah
>
>
>

Date: 16 Oct 2006 09:42:29
From: Peter Cole
Subject: Re: New Bike, Couple of Quirks

Date: 15 Oct 2006 18:44:20
From: Mike A Schwab
Subject: Re: New Bike, Couple of Quirks

http://sheldonbrown.com/brandt/shimmy.html
Brooks leather saddle is the best.
http://www.sheldonbrown.com/saddles.html
http://www.sheldonbrown.com/gears.html
Also be aware that there are additional index points to adjust the
front derailer to stop it rubbing the chain in various gears in the
rear. You may notice this as more that 1 click between gears.

D_Frumious_B@ndersnat.ch wrote:
<deleted >
> Three problems I've noticed with the new bike. One is serious TB after
> about the 40th mile. I suppose that tinkering with the seat will take
> care of that.
<deleted >
> I kind of wonder about my front shifter, though. Sometimes when I shift up from
> the small chain ring to the middle, it feels like the chain hasn't lined
> up quite right. And a couple of times when I've shifted up to the large
> chain ring, the chain has kept right on going. Fortunately, both times
> the peg between the sprocket and the crank arm has brought it back to
> where it got back on the teeth, but I sure hope that never happens to me
> in a tight spot.
> The problem that really has me baffled appears when I get the bike
> above 20 mph. Loosen my grip on the handlebars, or let go, and the bike
> starts to shimmy, with the greatest motion apparent in the head tube,
> which vibrates back and forth an inch or a little bit more at about two or
> three oscillations per second. It's not a problem as long as I keep a
> firm grip on the handlebars, but still it doesn't seem like that should be
> happening. It never did on my old Astra.
>
> Bill in Utah