The "is" models came with a BBS made basket wheel that measured 15' and your tire should fit just fine how ever if you want to keep the same rolling diameter you need a 205/55/15. Either will work, I am using a 205/50/15 on a set of aftermarket wheels that are 7' wide. I checked my speed on those local radar things and I am reading 1-2 MPH slow on the spedo.