Just got my bike back from the shop....?

Question

and it rides great but it wants to like shift on it own like the chain moves on the cassette all by itself.. I paid for the works... any tips why is it doing this? im going to call in the Am and take it back.. thanks

Answer 1

Could use a few more details if you could add them.  Does the chain move from gear to gear or does it just skip?  If it does move from gear to gear, does it move to a smaller gear or a larger one?  When you said you got the works, did it involve removing and cleaning the chain?  

Couple of ideas:  1. They removed the chain to clean it and then reinstalled it with a chain tool causing a "stiff link" in the chain.  This would cause the chain to skip eash time this link reaches the cassette.  2.  The rear derailleur is out of adjustment: either the cable is too tight (moves up an extra gear) or loose (moves down an extra gear).  3.  The chain, or cassette were replaced as part of the service and the two no longer match each other.  This can happen if you wait too long to replace your chain.  4.  Your derailleur hanger/rear derailleur is bent.  5.  Your shifter is broken.

I know....a lot of options.  More details in the question would help, but in any case, bring it back.

Answer 2

Take it back, they screwed up the derailleur adjustment.

http://bicycletutor.com/adjust-rear-dera...