Any advice on how to get the derailler to only shift into the small and middle rings? I can get it to shift using the small and big ring shifting points but I can't shift from small to middle without clicking the shifter all the way to the big ring detent point. I have tried the limit screws and unscrewing the bolt on the derailler clamp to the downtube to slide the derailler around and I can't get it to work. Any advice