[wilkin250r]

255/70R15 is just a hair over 10 inches wide. (255 is theoretically 255mm wide, which is 10.04 inches. Sidewall flexing outwards might bring that to about 10.5 inches)

In my experience and research, fitting a 10-inch wide tire on a 10-inch wide wheel only works with low profile tires, where the second number is 50 or below, really short sidewalls. When you start getting into the taller sidewall tires (where the second number is 65 or more), you really need the wheel to be a couple inches more narrow than the tire itself.

It's looking like most manufacturers of 255/70r15 tires recommend a 6.5 to 8.5 width for the wheel.