18*8 with a +40 offset isn't gonna be pretty, that's just askin for it. I have 18*7.5 with a +42 offset and I rub on occasion with people in the back seat, but nothing major, but if I was dropped more I'm sure it would be much more of a problem. Even +42 is a little low, I'd get at least a +45 if you can find a wheel that has that offset. Seems like all the nicer wheels have lower offsets.