Originally Posted by
headloss
Everything I've ever read has stated that the Tiagra road shifter works better paired with a mtb FD, although the only official word from Shimano is to use the matching FD (FD-Rxxx). I've read plenty of posts in which someone was complaining about the road/drop FD not working with the Tiagra flat-bar shifter.
I've personally built several of these conversion, most recently with 5700 105 Front and Rear Derailleurs and the Road FD shifts perfectly paired with this shifter set. There is a trim click that mimics the one found on the STI shifter which could cause some issues if not setup correctly. I actually find it a bit smoother shifting on the FD if anything...