DogBoy

Bike: Road bike, 10 spd rear centaur, 12-28. Front, FSA triple crank 28/38/50, ultegra Triple FD, Record brifters. 10 spd connex chain.

Problem. When in the four smallest cogs in the rear and in the 38 ring up front, the chain keeps riding up and then dropping back down into the pins. There is zero contact with the FD, and it happens if I spin the crank forward or backwards. In looking at the crank, I can find no real reason for it doing this, but it seems to happen regularly with a small chain shift to the outside of the bike (towards the big ring) The chain lifts up on the teeth and then drops back in. I cannot ride like this. The rear axle is straight and parallel to the crank, the crank is parallel to the frame. This setup has not done this in the past, but does now. Formerly on a Kona Jake the Snake Frame, now on a Specialized roubaix frame (broke the kona frame doing something stupid.)

Anyway, there is no derailleur contact so it isn't cable adjustment and I have now run out of knowledge. Anyone have any ideas?

bkaapcke

If you have a new chain on rings with lots of miles on them, it's time for new chainrings. That's the easy one. If not, you may have chainline issues. bk

DaveSSS 

I'm not sure that I understand the description of your problem. If you're saying that the chain wants to move over to the next cog (larger or smaller?) then you problem may simply be improper tension of the RD's shift cable. If it's too tight or too loose, the chain may decide to move to a bigger cog (too tight) or a smaller one (too loose).

RD hanger misalignment can cause all sort of odd problems. Never hurts to check it.

coldfeet

I'm guessing the chainline is different on the new frame, is there significant outward bend of the chain as it travels to the rear? That is, when in the 50 ring, does the chain look straighter in the middle cog, than in the 38 ring? If so, you need a wider BB, or spacers.

DogBoy

Closer inspection yielded a very good chainline, proper tension in the derailleur and two bent chainring teeth. Ordered a new chainring and bent them back for a temp solution until the new ring comes. Thanks for the ideas!