Shifting issues
im having some shifting issues on my bike.
its an 07 gmc XL road bike and the problem is when i try to shift to 1st 2nd or 3rd gear, the component moves but the chain remains on the same gear. i have to manually move the chain to the correct gear every time. its equipped with shimano revo-shifts if that helps. is there something i can do? or will i need to take it in a shop?im sorry i dont have picture but will be happy to clarify anything
thanks for the help