chainring wobble - fix it or ok to leave it?

In article <[email hidden]>,

sfcommuter said:

Brand new road bike build with a brand new 2003 Ultegra
Triple crank and I'm getting multiple "clicking" sounds
ONLY in the middle chainring.

My best guess based on everything I've read is that the
middle chainring is not true (is this common on new
cranks?).

Minor variations are not too uncommon on cheap cranks and
seen occasionally even on expensive ones. A wavy chainring
could be bent, or it could be mounted onto a crank arm with
a bent spider.

Quoted message said:

Because the teeth are staggered it is difficult for me to
tell but it looks like it is wobbling in places more in
the middle chainring when I watch it closely.

Where is the dealer in this equation? If this is a brand new
bike that doesn't work properly then it's the dealer's job
to make the bike work and explain to you how it works.

Quoted message said:

So my question is: what is the problem (aside from the
annoying clicking sound) if I just leave it like that? Will
it get worse or cause damage?

If the clicking sound is the chain rubbing on the front
derailleur cage, then it is not extremely harmful although
eventually you can damage the front derailleur. If you got
the bike from a dealer you could go ask them what is causing
the noise.

Quoted message said:

If I have to fix it, I'm afraid of making it worse since in
my reading it sounds like it could be any number of things
(arms, chainring teeth, etc.). Is this is a common problem
that is easy to fix? If so, how?

Well a front derailleur adjustment is the first and least
expensive fix to try.

Quoted post said:

Originally posted by Paul Southworth
[Minor variations are not too uncommon on cheap cranks and
seen occasionally even on expensive ones. A wavy chainring
could be bent, or it could be mounted onto a crank arm with
a bent spider.

Where is the dealer in this equation? If this is a brand new
bike that doesn't work properly then it's the dealer's job
to make the bike work and explain to you how it works.

If the clicking sound is the chain rubbing on the front
derailleur cage, then it is not extremely harmful although
eventually you can damage the front derailleur. If you got
the bike from a dealer you could go ask them what is causing
the noise.

Well a front derailleur adjustment is the first and least
expensive fix to try. [/B]

Thanks very much for the response. I built up the road bike myself so no one to fix it but me. 🙂 I was using Barnett's to attempt to diagnose and figured it must be the chainring itself because the other chainrings don't have any problems. It doesn't appear to be hitting the front derailleur cage.

I'm thinking the best option would be to take it to a mechanic with experience who could better judge whether the chainring has "normal" wobble or not. Perhaps someone has a more scientific method for determining whether the chainring is true other than just eyeballing it? (which is what Barnette recommended)

On Fri, 14 May 2004 22:20:01 GMT, sfcommuter <[email hidden]>

Quoted message said:

Thanks very much for the response. I built up the road bike
myself so no one to fix it but me. 🙂 I was using Barnett's
to attempt to diagnose and figured it must be the chainring
itself because the other chainrings don't have any
problems. It doesn't appear to be hitting the front
derailleur cage.

I'm thinking the best option would be to take it to a
mechanic with experience who could better judge whether the
chainring has "normal" wobble or not. Perhaps someone has a
more scientific method for determining whether the
chainring is true other than just eyeballing it? (which is
what Barnette recommended)

I don't know if this will help you actually straighten the
one bent chainring, but I did use calipers to measure the
runout of my chainrings.

Remove left crank.

Clamp a flat piece of material to the left side of the
downtube perpendicular to the floor. I used a small (2" x 2"
x 1/2"😉 piece of acrylic; wood would probably work.

Using the same point on this flat surface for each
measurement, I spun the right crank and made a series of
measurements with the calipers.

My problem was with the crank- a 4mm +/- wobble in the
same spot on both chainrings. I removed the chainrings,
measured the tab where the rings sit, and used a crescent
wrench to bend this tab in or out as needed. I got them to
within .003" of each other and reinstalled the chainrings.
No more wobble.

I don't know how you would straighten out a bent chainring,
but you could use this method to determine where and how
much the runout is on your ring and to check the effect of
any straightening operations.

Well, you did ask for a more scientific method 🙂

I'd take it to where you bought it and talk to them. Have
them put it on the stand and you show them what is
happening. A new crank shouldn't be out of round enough to
make rubbing or clicking noises.

Dan Daniel said:

... I don't know how you would straighten out a bent
chainring...

<http://www.sheldonbrown.com/straighten_chw.html>.