Back pedaling - chain comes moves to smaller sprocket
Hi - Just took my bike to the shop to have the bottom bracket bearings and the rear cassette replaced. Rear cassette is exactly the same as original. I have a cross country mtn bike with 2x10 gearing. Now when I back pedal, as little as a half a rotation, when chain is on the front largest ring and the rear is on the 1st or 2nd largest sprocket, the chain drops off the rear sprocket and goes the next one or two sprockets smaller in the rear.
Is that normal behavior or should the chain remain on the same sprockets during back pedaling in all gears? I don't think the bike was acting this this way before I took it in, but not 100% sure.
Thanks much for the feedback.
Ian