So I took my bike to the shop for the 12k service and he said I also need new chain and sprockets. is thins normal mileage to be changing the chain out?? thanks.
No. Unless you used battery acid to lube the chain, it should last thousands of miles more. Is the chain rusty? Has it reached the end of adjustment? Was it adjusted too tight? Is it noisy? Will the wheel spin freely? Are there kinks in the chain? Did he say why they must be replaced?