I'm pretty sure it's 8 inches wide. There has been a lot of debate over the widest tire that can fit on an 8 inch wide wheel...most say that 245 is the way to go, maybe 255 being the widest. Some say they fit 275 without a problem, but most say that is unsafe due to the tire bulging over the sides. I've never heard of a 285 on an 8 inch wide wheel, it would probably be very unsafe, even if it was able to fit.