Road bike shifters onto a mountain bike? An issue I had with trying to put road brifters on my
Scott sportster (my commuter) was the front shifter / derailleur was not compatible. Apparently, the MTB front der requires more cable pull to get from the big wheel to the little ( 3 spd). I could never get it adjusted for all 3 wheels ... I could get small and middle or large and middle but not all three. Had to abandon the brifters and go with barend shifters.

Not that you will have this same problem but might as well check for it first ...