Bicycle Mechanics - Freewheel cog worn out?

In servicing my bike just now, I found that my chain had stretched a bit, so I replaced it. My first ride, however, I discovered that the new chain skips when in the smallest cog on my freewheel - and ONLY in the smallest cog. The cog is not visibly worn out, so far as I can tell... all the teeth are nice and square and straight... Can anything else cause this?

Thanks!

-chris

I would say that if you did not make the chain to long it may be time for a new cassette.

I would say that if you did not make the chain to long it may be time for a new cassette.


Hmmm... If a too-long chain will cause it, I'd better re-count links just in case! The freewheel really doesn't look worn...

Thanks!

-chris

Most people wear the small cog out first. Then they learn how to keep their spin up.......

The samller cogs wear out faster becase each tooth is used more. The chain runs over the teeth on a 12 twice as much as a 24. Depending on the cassette/freewheel, you may be able to just replace the spefic cog, or the whole thing.

For anyone curious, this turned out to be caused by a twig or something that had gotten itself invisibly wrapped around the freewheel between the first and second cogs. I couldn't see it until I got the wheel off, and really looked closely, but it was enough to keep the chain from seating completely on that first cog. Got it out of there with a needlenose pliars, and everything's smooth running again!

In servicing my bike just now, I found that my chain had stretched a bit, so I replaced it. My first ride, however, I discovered that the new chain skips when in the smallest cog on my freewheel - and ONLY in the smallest cog. The cog is not visibly worn out, so far as I can tell... all the teeth are nice and square and straight... Can anything else cause this?

Thanks!

-chris

I've experienced similar symptoms after chain removal and reinstallation. Two things I've found to be common, the chain pin is the dark colored Shimano pin when you should be using the lighter silver colored one, or the pin wasn't seated properly. The dark colored Shimano pins are a teensie bit longer than the silver ones. The dark pin will catch on a neighboring cog and the chain then rides up and skips. Now I use a high speed grinder to polish the pin ends after I install them in a chain. This symptom won't show up on all of the cassette cogs. The improper seating of the correct length pin can cause the same results. It's worth checking out before replacing major parts.