Rear Wheel Troubles...

[DebW]

Check for damaged spokes behind your cassette. If some spokes are bent or gouged, those spokes should be replaced and the wheel trued. You most likely need to adjust the lower limit screw on your rear derailleur to prevent this happening again. And if the chain is worn/stretched, consider replacing it.

[navybeetle]

Check for damaged spokes behind your cassette. If some spokes are bent or gouged, those spokes should be replaced and the wheel trued. You most likely need to adjust the lower limit screw on your rear derailleur to prevent this happening again. And if the chain is worn/stretched, consider replacing it.

I have a plastic thing between my spokes and the sprockets (?) so I don't think the chain hit the spokes. I just bought this as a refurbished bike, used but all fixed up. I will check the lower limit screw, I dont know what a worn r stretched chain looks like. Thanks for your help.

[Owlie]

Here's the Sheldon Brown article on chains:
http://sheldonbrown.com/chains.html#wear
Scroll down a bit to get to the part about chain wear.