Originally Posted by XwChriswX

Yeah, I'd say nothing more than a 10mm, but a 5mm would probably be spot on.

The method I use is roughly 5mm < 1/4in and 10mm < 1/2in. So if you have a tape measure, just place it against the tire and look down from the fender and see how much tuck you have. Then that will give you a good idea of where you stand.