ok i know all should be changed together but my chain is still good and my front spocket is still good,but i my rear sprocket is warped can i get away with changing just the rear...be a waste to change a fairly new chain and front sprocket.

 

If your front sprocket and chain are in good shape, you can get away with just changing the rear. If you have a lot of ride time on the other components, I would look into changing them though as well. As cheap as front sprockets are, I would change that anyway, and then decide if the chain is worth changing.

 

An aluninum rear sprocket will quickly wear to fit a chain, even if it is a little stretched. I buy a new chain, front sprocket, and two rear sprockets. And, I figure on changing the rear sprocket out once during the life of the chain.