Thanks-
we suspected 47.5 was likely best bc he uses the middle ring the most on the streets of phila. We needed to see what the group thought- lots of knowledge/ideas here. Complicating factor is chain rub. When on the big ring-small cog, the chain rubs the front der outer plate. Can adjust this out with cable tension, but then the chain rubs the inner der plate when in the middle ring-big cog position. Can't have it both ways. Installed a tiny washer between the cage plates at the rear of the front der for extra clearance-this helped a little but rub remains. Hence, the chainline question. Can this be solved, or is it too much to ask for on a nine speed triple? There is no trim function.