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Old 04-24-07, 07:21 PM   #1
jankon73
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Chain skipping, cant find the culprit!

Hello, all!
I've got an odd chain skip problem, I was hoping someone might have some input to share.

I just got an awesome, older 7 speed Trek 950 Singletrack from the thrift store that skips under load. I gave it a new 7 spd chain, a new 7 spd RD, and a thorough tune up and cleaning. Cassette teeth are sharp and clean, not rounded off. New shifter housing and cables, everything tensioned and shifting like butter. Hanger does not look bent and it has all compatible LX components for this part of the drivetrain.

The old RD looked fine but swapped it to make sure it wasn't the problem. Still skips.
Pawls are engaging. Made it a singlespeed on the cog ratio it skips on, and everything engages just fine.
The search function is great, I learn a lot around here, but this has me stumped.

I've spent hours and hours on it, I'm about to take it to the 15 year olds at the lbs to see if they can do anything.

I guess my question is: What else COULD it be? Thank you!
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Old 04-24-07, 07:32 PM   #2
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Quote:
Originally Posted by jankon73
Hello, all!
I've got an odd chain skip problem, I was hoping someone might have some input to share.

I just got an awesome, older 7 speed Trek 950 Singletrack from the thrift store that skips under load. I gave it a new 7 spd chain, a new 7 spd RD, and a thorough tune up and cleaning. Cassette teeth are sharp and clean, not rounded off. New shifter housing and cables, everything tensioned and shifting like butter. Hanger does not look bent and it has all compatible LX components for this part of the drivetrain.

The old RD looked fine but swapped it to make sure it wasn't the problem. Still skips.
Pawls are engaging. Made it a singlespeed on the cog ratio it skips on, and everything engages just fine.
The search function is great, I learn a lot around here, but this has me stumped.

I've spent hours and hours on it, I'm about to take it to the 15 year olds at the lbs to see if they can do anything.

I guess my question is: What else COULD it be? Thank you!
I believe the cogs are worn even if they don't look like it. It only takes a small amount of wear to change the tooth pitch enough that they won't mate with a new chain.

I once put a new chain on a cassette that I was sure looked brand new and the previous chain had only "stretched" less than 1/16" in 12". It still skipped on the 15T and 17T cogs.
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Old 04-24-07, 07:33 PM   #3
robhunterx
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New chain on old cogs in the back will usually result in this 'skipping' problem. Sounds like you need a new freewheel or cassette to properly mate up with that new chain. Good luck.
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Old 04-24-07, 07:46 PM   #4
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Check your chain for a stiff link. Slowly rotate the crank backward and observe the jockey pulleys. A stiff link will cause a noticeable jump. Takes 10 seconds.
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Old 04-24-07, 08:00 PM   #5
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I agree with checking for the stiff link first. I sometimes have a similar problem after I break the chain, clean it off the bike and then reinstall it.
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Old 04-24-07, 08:32 PM   #6
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No stiff links.
I'll swap out cassettes, see what happens. Thanks for the input, guys!
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