Shimano 9 speed left hand shifters
I am currently using a Shimano Tiagra ST 4500 9 speed shifter set for a 9 speed rear setup and a 10 speed compact front mech and ring setup. This all works perfectly as I believe the pull ratio for 9 and early 10 speed front mechs is the same. This being the case, when Shimano brought out the early Tiagra ST 4600 10 speed setup, what changed on the left hand lever? Were there cosmetic changes or did they change the internals as well? Or, are they identical?