What is the difference of a 26" rim to 24" rims?here some of the downhill riders using different size of rims in the front they're using the standard mountain bike rim which is 26" @ the rear they're using a 24"fat boy rim,is there any difference in performance or is it just look good?could anyone help me on this coz i can't make mind if im goin to change my rear rim to 24"?