Davidlean

I have a SRAM PG-950 9-speed cassette 12-26 and a 9 speed chain on a bike that is several years old. I recently noticed that in one middle gear I get a slight click sound each revolution. Anyway, I put the bike on a stand to look at it carefully. Sure enough, spinning through the combinations, I found that there is one tooth (I think it is on the 15 ring) that briefly catches a chain link when it is in the next ring. There is a soft click as the chain is released. I looked at it carefully and the tooth doesn't look any different than the others, but that is the only one causing the sound. Add'l info. The rear derailleur looks straight and the indexing shifting seems to center the chain spot on.

I did notice that if I pulled the rear derailleur down just a touch, it doesn't happen. I adjusted the b-screw on the derailleur and it seems to help, but it hasn't completely gone away when I ride.

Now I admit this is a minor problem. The chain is not worn down (I measured it) and the cassette looks fine. I lubed the chain fairly often. I guess I could just ignore it or replace the cassette or... what? Perhaps a 10 speed chain that is narrower might not catch a tooth on the next ring. Is that a better way to go? I heard that 10 speed chains don't last as long, is that true?

I sometimes wonder about taking a file to that one tooth, but I don't want to create other problems. Suggestions?

FBinNY 

That's a loose sprocket cassette. take it off and lay the problem sprocket on a table to see of maybe the one tooth is bent a bit out of line. If so a bit of filing can only help.