Chain sometimes jumps. New parts

Question

Can't seem to get to the bottom of this. I have an 1997 Marin Eldridge Grade. I use it mostly for touring. The chain jumps or skips. It doesn't Jump down to a smaller sprocket. What the chain does seems like it could be several things. 1.It could be riding up on the sprockets 2. It could be riding up on a chainring 3. It could be a pawl skipping. The problem is, pretty much everything is new. New LX chainrings,New chain Probably a Whipperman Connex 808, 8 sprocket XT cassette, and a new freehub. It doesn't skip/jump all the time and i think it is more inclined to do it at moderate load. It seems to be getting worse. I've been a cyclist for 43 years and can sort most things out myself but this is doing my head in.

Chain is not jumping up and or down sprockets so not changing gear. It is riding up on teeth of sprockets or chain rings. I have already stated that chain is new. Shifter and Derailleur are Shimano XT. No stiff links in chain.

Answer 1

Even though the chain is new, you could have a stiff link. I assume you cut the new chain to get the correct length. If so I'd start there to make sure you didn't mess up the first remaining link. Then I'd manually check each link for a stiff one. If you find a stiff link, you can sometimes loosen it up by bending it a bit side to side. That is at 90 degrees to plane of the pivot.

Answer 2

I would suggest double checking the lock ring on your cassette and the cones on your rear hub.

You may also check if your rear derailleur hangar is bent. And if it's replaceable it could be loose - if so, remove it, clean the screws and threads, and use loctite on reinstall.

Check your quick release. Bent frame?

With regard to your point about pawls, I actually experience an interesting issue with my freehub (Novatec) where it can "pop" after freewheeling. I don't know what causes it, but I think it has something to do with a ring of some sort that holds the pawls in place (and being a cheap hub.) Have you tried removing the cassette and free hub to inspect the pawls?

You said everything is new - what about derailleur cables and housings? Are housings seated properly in the cable stops? Does your problem only tend to occur on shifting to a higher gear, suggesting that the cable may not be able to glide smoothly in the housing, keeping the derailleur indexed lower so that the chain is "riding up on the sprockets"?

Chain slip seems unlikely with new cassette and chain. Riding up on a chainring seems unlikely too - you'd probably hear the chain rubbing on the rings all the time, but double check for a bent ring and any bent teeth that could catch the chain.

Can the rear derailleur pulleys rotate freely? If they stick it would cause the derailleur to put tension on the chain until the sticky pulley is overcome by force. On a similar topic, take your rear wheel out and spin it in your hands (holding it by the cones) to check your hub bearings.

This is just a brain dump from my own experience, your note about moderate load does lead me to rear derailleur and hanger issues though.

One more thing: I assume there's three chain rings, does this happen when you're in the small ring and smallest cog, middle ring and largest or smallest cog, or big ring and largest cog?

Answer 3

I had problems similar to yours because the indexed lever I was using to change gear was slipping under the tension exerted by the spring in the rear derailleur.

Another possibility is damaged chain rings. You can diagnose this by adjusting the derailleur initially so that it is in a middle gear. If the chain is still skipping under load, that would suggest damaged chainrings.