This is referring mainly to the FR500's, but could also apply other reps like the Bullitts and whatnot. In an 18" rim, they offer a max width of 10" (ie. 18x10). However, for whatever reason, the 17's offer a 10.5" width (ie. 17x10.5). My question is simply if the actual dish surface on the 17x10.5 is larger than the 18x10's.....or is that extra half inch found elsewhere in the wheel?