I can't remember all the different sizes I've run on mine over the years, but most recently I had 14x6 Cragars with 225/60/14s all around, now have 15x7 Cragars with 225/60/15s. The 15's have more backspace and actually fit better in the back than the 14s. On the rear of my 65 Barracuda, there is half an inch or more variation in clearance from one side to the other. With passengers in the back, the 14's LR tire would rub slightly when going over a dip at speed. Never happens with the 15s.
Front was no problem with either size on my 65 Barracuda, but on my 63 Valiant with the same wheel/tire combo I did have to trim the lower front of the left wheel opening a slight amount when I converted to 15s as the LF tire would rub ever so slightly on a hard left turn. The cut is modest enough that it is not noticeable unless you know it's there.
Point, though, is that there are clearance variations between one side and the other, and one car and another despite both supposedly having exactly the same wheel openings.
