The 21F/18R is a nice looking set up,but I don't know how it would handle.The 19 doesn't come in a 3.50 width on the front though!!!!!Thinking logically I think the 21F would change the rake a tad bit but I could be wrong!!! If it does don't expect the bike to turn in to quick.The turning radius would be different.It would also change the center of gravity on the bike making it taller & more top heavy!!! I could be wrong though!!!!