Chain skipping when on bumpy road

furrag
furrag Posts: 481
edited January 2011 in Workshop
When I'm riding hard on bumpy roads, I'm finding my chain is skipping down into a smaller sprocket (higher gear). It shifts fine across the cassette and is very very quiet when pedalling and shifting.

I recently lengthened the chain as it was a little too short and I'm thinking I've probably made it a little too loose and taken too much tension out of it. Before I shorten it, I want reassured that lengthening it excessively is probably causing the chain to jump down the cassette?

Comments

  • John.T
    John.T Posts: 3,698
    Have you got the 'B' screw adjusted correctly. The top jockey should be quite close to the sprockets. If I turn my bike upside down it actually catches but I don't have any phantom changes.
  • Put your chain on small/small and tighten up. The chain on the bottom run should be taught - the spring in the rear mech pulling it taught. If the rear mech completely doubles back on itself and the chain on the bottom run is slack, the chain is too long.
  • John.T
    John.T Posts: 3,698
    Put the chain on big ring and small sprocket. The jockey wheels should be vertical one above the other.
  • darren H
    darren H Posts: 122
    Why did you lengthen it
  • furrag
    furrag Posts: 481
    darren H wrote:
    Why did you lengthen it
    I built it from the frame up. Followed bicycletutor's & Sheldon Brown's "put it on both largest sprockets front and rear with the chain not threaded through both mechs" approach, and it resulted in a super tight chain which pulled my rear mech forward aggressively when in 39x12.

    I'm running Campag. I tightened the 'A tension' screw and it certainly has taken it a lot closer to the sprockets - about 1cm. I'll try it out tomorrow. It's not much fun trying to fix a bike close to midnight with a torch in your mouth which makes you salivate like a St.Bernard!