Chain slipping off bottom jockey wheel

starbuck

I have a 3x9 setup with an XTR front mech and an XT shadow rear mech.

If I'm in the middle front ring and 1st or second gear at the back, the chain slips off the bottom jockey wheel a bit. It's then seated fine again when I change to 3rd gear.

If I'm on the big ring at the front, same thing happens in first and second gear, but it doesn't go back in perfectly again until 5th gear.

The chain never comes off the jockey wheel completely, just gets very rattly until I change gears (as above, depending on which ring I'm in up front).

Any ideas what the issue could be?

02gf74

that's unusual. has it started to do it recently, do it fter a change?

could be worn chain or wron jockey wheel , wrong length chain, indexing not adjusted correctly, b-stop adjustment incorrect

really need more info.

JGTR

Mate had this, was a bent derailleur hanger in the end and needed a link removing from the chain as had had new chain fitted.

The Rookie

Check the jockey wheel bearing, a mate had this and then the chain jammed in the mech, the bottom JW bearing was fubared and allowed the jockey to tilt and the chain come off.

Pedal forces make short work of a derailleur cage if the chain jams in it.....

cooldad

This ^^^^^

I had the same issue and swapped the wheels from a bent mech. Problem solved.

starbuck

Just ordered some new jockey wheels (and found a new gear hanger from superstar for £8) so hopefully one of those should sort it out.

The Rookie

Well it would have made sense to check before buying.......