The used rims I just bought have the 255/60-15s on them and they fit on the back fine, but my concern is that the offset is 4 inches and most people on this forum say that an 8.5 inch wide rim should have a 4.5 inch backspacing so I'm concerned I might be a little too close to the outside of the car with the wider and potentially taller tires. I have no intention of using them up front - probably go with 245/60-15. Thanks for the response.