Chain Skipping after Wreck

derailure and drop out alignment are often the culprets after getting
the back end dinged..

may have said:

I'd like to understand the dynamics of chain skipping. I have a few
slightly "dented" teeth in the back but it doesn't look like much. My
rear derailleur also got bunged up and I'm sort of wondering if reduced
chain tension could be playing a role?

If the teeth are bent sideways, take the cassette apart and bang them
flat with a hammer on a steel plate. If the teeth are bent forwards
or backwards, replace the cassette, or at least replace the
sprocket(s) that have the bent teeth. Fix the sprockets first, then
evaluate whether the der is a problem. If the der is bent, IMO it's
best to replace it.

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Werehatrack said:

Quoted message said:

I'd like to understand the dynamics of chain skipping. I have a
few slightly "dented" teeth in the back but it doesn't look like
much. My rear derailleur also got bunged up and I'm sort of
wondering if reduced chain tension could be playing a role?

If the teeth are bent sideways, take the cassette apart and bang
them flat with a hammer on a steel plate. If the teeth are bent
forwards or backwards, replace the cassette, or at least replace
the sprocket(s) that have the bent teeth. Fix the sprockets first,
then evaluate whether the der is a problem. If the der is bent,
IMO it's best to replace it.

The freewheel is less than a year old and shows very little wear other
than a few "chain dented" teeth on the 13T sprocket. With a new
well-lubed chain I have skipping in the three highest gears. It could
be the new chain is slightly too long as I went from a 114 to a 116
because I had gone from a 12-28 to a 13-34 freewheel earlier. I plan to
reinstall the 12-28 to see what effect that might have.

Thanks

check the derailure alignment .. really..

Quoted message said:

check the derailure alignment .. really..

As in maybe the chain is not being centered on the sprocket? I don't
hear anything like that happening. It doesn't sound like it is in
mid-shift.

Thanks

Not really a centering issue ..even a slight mis-alignment of the
derailure will impart a torque (for want of a better word) to the chain
that can cause it to more easily miss shift. Depending on the angle of
the bend and its severity it can be something as a slight reluctance to
downshift (the chain rides to the top of the sprocket but does not
drop to the lower one). A tendency to over shift .. drop two gears
instead of one, when going down or try to go up two instead of one
causing a rattling noise.. all sorts of things all depending on the
severity and direction of the bend.

Put the bike in a stand or hang it run the pedals around quickly and
run through all your shifts. I suspect you will find one or two gears
that seem reluctant to engage, either when going up or going down..

Hard to diagnose via usenet but if you walked into my shop saying what
you've posted here I would expect to have had you fixed up in under ten
minutes.

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

Quoted message said:

If the teeth are bent sideways, take the cassette apart and bang them
flat with a hammer on a steel plate.

Oh boy, I thought I was the only one stupid enough to ever try that.
It doesn't work, it'll bend back very rapidly...

To Dave, I would say that it seems perfectly normal. Dented teeth--->
skipping chain, it's just the way it is (don't ask me about the
physics behind it though). Bented teeth after one year of riding
sounds very normal to me, anyone with different views on this subject?
In fact better than normal, I would say (specially if you ride dirty
roads in bad weather conditions). I suspect that cassettes driven by
stonger riders are more prone to that sort of damage. In my experience
(just experience, not theory), riding with a worn chain accelerates
the process of damaging the teeth in a huge way! All kinds of
alingement-issues could (but here I'm just going on intuition) also
play a role, as suggested above...

I stopped riding derailleur-bikes for that, skipping chains are in my
mind a big safety-issue.

(aleksandr) said:

[...]
To Dave, I would say that it seems perfectly normal. Dented
teeth---> skipping chain, it's just the way it is (don't ask me
about the physics behind it though). Bented teeth after one
year of riding sounds very normal to me, anyone with different
views on this subject? In fact better than normal, I would say
(specially if you ride dirty roads in bad weather conditions).
I suspect that cassettes driven by stonger riders are more
prone to that sort of damage. In my experience (just experience,
not theory), riding with a worn chain accelerates the process
of damaging the teeth in a huge way! All kinds of alignment-
issues could (but here I'm just going on intuition) also play a role,
as suggested above...

Well, I can see "chain dents" on a few teeth of the smallest sprocket
(13T) but not the next two sprockets which also skip. I never realized
you could have chain skipping with unworn teeth and a new chain.

Quoted message said:

(aleksandr) said:

[...]
To Dave, I would say that it seems perfectly normal. Dented
teeth---> skipping chain, it's just the way it is (don't ask me
about the physics behind it though). Bented teeth after one
year of riding sounds very normal to me, anyone with different
views on this subject? In fact better than normal, I would say
(specially if you ride dirty roads in bad weather conditions).
I suspect that cassettes driven by stonger riders are more
prone to that sort of damage. In my experience (just experience,
not theory), riding with a worn chain accelerates the process
of damaging the teeth in a huge way! All kinds of alignment-
issues could (but here I'm just going on intuition) also play a
role, as suggested above...

Well, I can see "chain dents" on a few teeth of the smallest
sprocket (13T) but not the next two sprockets which also skip. I
never realized you could have chain skipping with unworn teeth
and a new chain.

As an update I replaced the freewheel and this fixed the skipping. I
have to conclude that even the sprockets that I thought were unworn
must have been critically worn -- at least for use with a new chain.
The "dents" on the 13T sprocket must have been the damage from the
wreck.