Actually, the opposite is true. The smaller wheel offers the tire LESS leverage against the disk/caliper, so the brake feels stronger/lighter. I'm about to give up on trying to find a 320mm caliper spacer, and go with the stock 300mm rotor and some Motard wheels. I have two sets for SX/EXC, both have 320mm front disks. The back wheels won't fit. I'm tempted to spend big on the KTM Twins tubless option, but a little more Reserch into fitting the forged 2013 Duke wheels first. Anyone got any further info? (from above, seems the Duke disk bolt pattern, and the fact the Duke disks are the wrong size is the first problem. I have seen older SMs/SMCs with older Duke wheels fitted. Not sure how much "engineering" was required.) I find riding my KTM690 a return to pure riding pleasure (road biased Pirelli MT90s). I have several great bikes (ok 7), but while away at work I think about my 690 the most.. Oh and my GF!