Are you sure you have the right chain length? I think shimano says over the front large ring and over the rear large ring plus 2 for MTB or something like that I forget (think ZINN says plus 4 for road bike?). This is a general rule to let you have plenty of chain, Im sure you could make it shorter but would make the chain under higher tension on the return (bottom) which might be what you want, but the RD will be taking more stress though.