There seems to be an endless stream of folks asking about the best backspace. I think there is a good reason for this - it's because thinking in terms of backspace will never get your head straightened out about wheel and tire position. I suggest (as I and others have before) that instead, you think in terms of wheel offset and wheel width, and then also tire tread and section width. It's just easier to understand and compare 2 wheels to each other that way. BTW, there are just as many issues with the outside edge hitting fenders and flares as the inside edge. That would be frontspace. Does anyone know their wheel frontspace? Not likely. Wheel offset tells you about both. FYI, OEM 80 series wheel offset (ET)=0mm and width=8inches.
