I'm looking to replace a 28/38/48 crankset with a 22/32/42. My front derailleur is top mounted, clamped to the seatpost, bottom swing, top pull. Since the tooth differential between the smallest and largest chainwheel is the same, could I assume that the FD would still work, but that I would need to unclamp it and slide it down (and possibly install a longer cable)? I'm sticking with the same brand (Altus). The current one is approx 1993 year model.