There is another potential problem. Assuming your crank has the original 52/42/30 chainrings, the substitution of a 48T for the largest ring and lowering the front derailleur so it's positioned properly may cause the inner cage of the front derailleur to hit the 42T middle ring. Most current front derailleurs are spec'ed for a 10 tooth or more difference between adjacent chainrings and that 6T difference may cause interference.