Chain trying to jump to another gear on backpedal

roger645

Had my bike serviced recently and new chain and cassette fitted. When I backpedal the chain try's to jump to another gear on the cassette and jams. Is this an adjustment problem? Set up is 105 with Ultegra rear dérailleur.

cougie

Slightly misaligned I would say - you should be able to fix this with adjusting the collar on the rear mech - clockwise or anticlockwise - whichever way it is to ensure that the jockey wheels are directly below the sprocket you want.

But dont back pedal more than you have to.