Originally Posted by
Sjtaylor
The derailleur is shimano FD-4503 so I guess the pull ratio is wrong for the mountain bike shifter. I'll try the Deore XT fd tonight.
Most mountain bike derailleurs are designed for much smaller chainrings than the ones on your bike. The curvature on the derailleur cage is matched to the 42 or 44 tooth big rings on most mountain bike cranks. It may work better than your current setup and I hope it does, but the best solution is a flat bar shifter matched to the stock derailleur. Something like this:
https://bike.shimano.com/en-EU/produ...L-R2030-L.html