ok, i got a flat on my truck a while back, my buddy said thank god it was on the front wheel (its a 2wd btw). i asked him why, and he said if it was on the back, putting the smaller spair on, would have ****ed up my differentials. i have an open diff. too. if it was just a slightly smaller wheel, driving on it wouldn't mess it up would it? its just like turning in a circle right?