My '97SL has a 5.5 rim and was originally wearing a 170 section rear. Sticking a 180 presented no clearence problems at all, and i'm sure that if a 180 fits onto a '97, then it will go on to a ie. Oddly there seems to be no difference with the tyre widths

... (from Dunlop 207 170 to a Metz racetec 180).