Uneven Chain Wear?

(PeteCresswell) said:

Just checked the wear on my MTB chain with one of those little tools
where you lay it on the chain and if it lays flat the chain needs
replacement.

Checked one area, and it seemed to have plenty wear left in it.
Checked another area, same story.

Checked a third area and that sucker was laying *flat*...with a
little slack yet.

Seems like at least 8" of the chain is worn much more than the rest.

This chain has never been spliced or had links added to it.

Doesn't make sense.... or does it?

Duh. The bottom section of chain between the front ring(s) and rear
derailleur cage will always stretch perceptibly more than the rest of the
chain due to tension and gravity.

You DO always store the bike with the chain attached, right? Try rotating
the cranks a quarter turn each night.

Bill "this one's for JB" S.

(PeteCresswell) said:

Seems like at least 8" of the chain is worn much more than the rest.

Is there a removable link involved?

Per Ron Ruff:

Quoted message said:

Quoted message said:

Seems like at least 8" of the chain is worn much more than the rest.

Is there a removable link involved?

Yes.
--
PeteCresswell

Per Bill Sornson:

Quoted message said:

Duh. The bottom section of chain between the front ring(s) and rear
derailleur cage will always stretch perceptibly more than the rest of the
chain due to tension and gravity.

You DO always store the bike with the chain attached, right? Try rotating
the cranks a quarter turn each night.

Sounds logical, but the measurements were taken immediately following a 2.5 hour
ride.
--
PeteCresswell

Pete Cresswell wrote:

Someone locally had a similar story, using some sort of "chain
checker."

Are the results repeatable? Have you tried measuring nominal 12"
sections of the chain with a ruler to verify these variations? I agree
that it doesn't make sense that parts of the chain would be worn and
other parts not.

http://www.execulink.com/~dtierney/wmc/SRAM/chains2.htm#Chain%20wear

Art Harris

Duh, chains don't stretch!!!! The apparent length increases due to pins
wearing...

Bill Sornson wrote:
[snip]>

Quoted message said:

Duh. The bottom section of chain between the front ring(s) and rear
derailleur cage will always stretch perceptibly more than the rest of the
chain due to tension and gravity.

You DO always store the bike with the chain attached, right? Try rotating
the cranks a quarter turn each night.

Bill "this one's for JB" S.

(PeteCresswell) said:

Per Bill Sornson:

Quoted message said:

Duh. The bottom section of chain between the front ring(s) and rear
derailleur cage will always stretch perceptibly more than the rest
of the chain due to tension and gravity.

You DO always store the bike with the chain attached, right? Try
rotating the cranks a quarter turn each night.

Sounds logical, but the measurements were taken immediately following
a 2.5 hour ride.

Sounds logical?!? Pete, Pete, Pete...

Bill "wanna invest in my star-naming biz?" S.

richard top-posted (shock et surprise):

Quoted message said:

Duh, chains don't stretch!!!! The apparent length increases due to
pins wearing...

Bill Sornson wrote:
[snip]>

Quoted message said:

Duh. The bottom section of chain between the front ring(s) and rear
derailleur cage will always stretch perceptibly more than the rest
of the chain due to tension and gravity.

You DO always store the bike with the chain attached, right? Try
rotating the cranks a quarter turn each night.

Bill "this one's for JB" S.

Whoosh.

Bill "WHOOSH" S.

<snippage of BS>

Depends on what direction you tension the chain. The pins only wear on
one "side".

D'ohBoy

(PeteCresswell) said:

Just checked the wear on my MTB chain with one of those little tools where you
lay it on the chain and if it lays flat the chain needs replacement.

Checked one area, and it seemed to have plenty wear left in it. Checked
another area, same story.

Checked a third area and that sucker was laying *flat*...with a little slack
yet.

Seems like at least 8" of the chain is worn much more than the rest.

This chain has never been spliced or had links added to it.

Doesn't make sense.... or does it?

Bill S. suggested you might be measuring the chain above and below the
chainring... that could be part of the issue...

Or perhaps the chain is both worn AND dirty. I can imagine that a
chain that's had a liberal application of dirt to a specific area
might tend to mesure better than the other portion that might be
cleaner (since it's not unthinkable that that grunge could work its
way into the worn areas inside the rollers).

Or maybe rust is the answer... if your chain was stored wet, but not
uniformly so (or perhaps lubricated more on one portion than another),
rust could be forming inside the rollers on only certain portions of
your chain. Again, this would tend to make the chain check "better"
in the rusty area.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

D'ohBoy said:

<snippage of BS>

{Typical removal of content rendering your comments /extra/ puddinheaded}

Quoted message said:

Depends on what direction you tension the chain. The pins only wear
on one "side".

Unless you change the properties of a spring, the rear derailleur cage will
ALWAYS pull the chain in the same direction.

Bill "duh D'oh" S.

{mutter: can't believe they're biting on this, but hey...}

Mark Hickey said:

(PeteCresswell) said:

Just checked the wear on my MTB chain with one of those little tools
where you lay it on the chain and if it lays flat the chain needs
replacement.

Checked one area, and it seemed to have plenty wear left in it.
Checked another area, same story.

Checked a third area and that sucker was laying *flat*...with a
little slack yet.

Seems like at least 8" of the chain is worn much more than the rest.

This chain has never been spliced or had links added to it.

Doesn't make sense.... or does it?

Bill S. suggested you might be measuring the chain above and below the
chainring... that could be part of the issue...

Sigh. Et tu, Mark?!? What I /suggested/ (with pinky firmly tucked in palm)
was that the der cage TENSION "stretches" that part of the chain more than
the rest. (That's why I also "suggested" that he move the cranks a quarter
turn each night to rotate "that part" of the chain.)

I guess I forgot to activate the SARCAMS MODE! :-P

Bill "that little smiley tongue ISN'T in the cheek" S.

Per Bill Sornson:

Quoted message said:

Sounds logical?!? Pete, Pete, Pete...

I can envision it.

Bike hangs from the front wheel for a few week. The part of the chain that's
wrapped around the front chainwheel doesn't have any weight on it, the rest of
the chain is just hanging there on the rollers and the oil or whatever that
they'd be floating in gets squeezed out and the rollers settle downwards.

Then somebody takes it off the hanger, puts it on the floor, measures the chain
as-is, and finds those links are worn "X" amount.

Then they rotate the pedals a little - which moves the protected area out into
the chain line so that the tool spans protected and settled links - and it looks
like there's "X+n" wear.
--
PeteCresswell

D'ohBoy said:

<snippage of BS>

Depends on what direction you tension the chain. The pins only wear on
one "side".

Which is why I always remove and rotate all my chain's pins every
1,000 miles.

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

Bill Sornson said:

Mark Hickey said:

(PeteCresswell) said:

Just checked the wear on my MTB chain with one of those little tools
where you lay it on the chain and if it lays flat the chain needs
replacement.

Checked one area, and it seemed to have plenty wear left in it.
Checked another area, same story.

Checked a third area and that sucker was laying *flat*...with a
little slack yet.

Seems like at least 8" of the chain is worn much more than the rest.

This chain has never been spliced or had links added to it.

Doesn't make sense.... or does it?

Bill S. suggested you might be measuring the chain above and below the
chainring... that could be part of the issue...

Sigh. Et tu, Mark?!? What I /suggested/ (with pinky firmly tucked in palm)
was that the der cage TENSION "stretches" that part of the chain more than
the rest. (That's why I also "suggested" that he move the cranks a quarter
turn each night to rotate "that part" of the chain.)

I guess I forgot to activate the SARCAMS MODE! :-P

I wasn't thinking "stretched", I was thinking "sagged".

Quoted message said:

Bill "that little smiley tongue ISN'T in the cheek" S.

That might look like.... :-?=

Mark Hickey
Habanero Cycles
http://www.habcycles.com
Home of the $795 ti frame

<more BS snippage>

Merry Christmas, Bill. I hope you liked it.

D'ohBoy

P.S.: If it's not on the bike ..... ;-)

I post:

Quoted message said:

Quoted message said:

Depends on what direction you tension the chain. The pins only wear on
one "side".

To which Mr. Hickey responded:

Quoted message said:

Which is why I always remove and rotate all my chain's pins every
1,000 miles.

Mark, you're not too far off:

The pins do wear only on one side - if you fix one end of a worn chain,
and then "stretch it ", it will measure much more with the vector of
the tension in line with the tension of the pedaling cyclist applied to
the chain than with the opposite (no wear on those "sides" of the
pins). One could reverse the "direction" of the chain at about half
its normal life and get no more miles out of it until the pins were
dangerously thin.

BUT - you will significantly reduce the wear on your cogset due to
improperly spaced chain pins due to wear.

Am I making sense?

D'ohBoy

Per Mark Hickey:

Quoted message said:

Or perhaps the chain is both worn AND dirty. I can imagine that a
chain that's had a liberal application of dirt to a specific area
might tend to mesure better than the other portion that might be
cleaner (since it's not unthinkable that that grunge could work its
way into the worn areas inside the rollers).

I'm going to take that one and run with it.

This chain *is* kind of nasty - even more grit than usual. I guess it was that
last ride at the bay beach where I windsurf....-)

Although I'd think that grit would induce a more optimistic measurement by
preventing the gauge from seating fully - whereas this is a case of the gauge
sinking in all the way just sometimes.... in fact right now, it looks like only
at this particular link.

http://www.cotse.net/users/fatbelly/GoofeyChain.jpg

I think I'll clean it up, re-measure and see what comes of it.
If nothing else, maybe I've discovered a link on the way out before it failed in
service.
--
PeteCresswell

"Mark Hickey" wrote: Which is why I always remove and rotate all my
chain's pins every 1,000 miles.
^^^^^^^^^^^^^^^
Clearly, then. what has happened to Pete Creswell's chain is that during the
last maintenance, he lost track of where he started the pin rotations, and,
either didn't complete the job, or went too far and returned some of the
pins to their original positions.

BTW, I tried reversing the tension on the chain, hoping to utilize the
unworn sides of the pins, but I must have done it wrong. The chain went
into compression, and the bike ran backwards.