okay, last post on the subject. at about 30 its actually doing 32, at 70 its about 75It shouldn't be possible to have the same error at all speeds. The extra distance travelled will increase as a percentage so the speedo error will change too.
That's unusual. I've read a lot of these 235/65/17 threads and the only time that I recall the speed being more than 1 mph out (at high speeds) was on a 16" chassis.