Big ring chain crunch/jump on crossover gears

jamesbarlow300

Hi folks, I run shimano 105 compact group set on my foil. Problem I'm having is crunching and chain hop on the front chain rings when I go up to 28t rear. Thought it was crossover, but does it on Small chain ring too.

Looked at wear, chain is OK, rear cassette is fine (I run two sets) but front chain rings were small OK large worn too needles. Thought it was that so changed front 50t ring. That didn't cure it and that's when I discovered it did the same on the small front ring.

Chain hop is every half turn of the drive and this seemed to start when a new bottom bracket was installed by the shop (press fit).

Any ideas?

jamesbarlow300

I should add....

When I come down towards 11t on the rear, the problem goes away.

ArgonDon

Hi mate two thoughts first has the B screw been adjusted, it should be bringing the chain as close as possible to the cassette when in 28, most likely cause.
second to the chain being worn, assume this only happens under load, could it be your bike shop reversed the chain, so the wear is now on different faces of the chain, unlikely and a bit far fetched but worth a try!

jamesbarlow300

The derailleur adjustments/settings are perfect, chain was not touched. This is nothing to do with pressure.
When I'm on the 3 bigger rear sprockets the chain is crunching and hoping every half turn. As I come down at the rear to small(11t) the crunching goes away.
I'm going to try a new chain but Don't think it will help.

ArgonDon

Hi James, logically it can only be worn chain/sprockets or and this would be odd if the rear wheel or cassette was out of alignment, would be magnified on the bigger cogs.......

jamesbarlow300

Two sets of wheels, two sets of cassettes so not that. As I mentioned, the BB was replaced and I'm wondering if it's not in straight (pressfit) if that could be it.