brakes are a definite. hell, they're already on the bike..and cantilevers at that. gear? hmmm...running 34:18 now on the mtb ss (about to be 33:17 for the no-convert magic ratio on a frame with horiz drops). this is where the inexperience specific to fixed mtb comes in. i am thinking about 32:18ish since i am comfy there, unless i am missing something. could go 34:19/20 if necessary.