Messing around with Ruby(my 1 ton panel)today and noticed that my rear tires seemed to fill their respective fender wells differently. I got out a tape measure and checked the diameter of the tires and found that one was 28.5" and the other was 29.0"! Both are Michelin 265/75/R16 same markings,same type. Who woulda thunk it!!
Swapped the spare(29.0") for the 28.5" and got rid of a persistant differential whine. I thought that tires with the same stated size would be the same actual size. These weren't cheap tires, so if you have a pesky, peristant rearend noise, it may not be gas... check your tire sizes with a tape.
