well if you want to be super accurate, you would find the actual CIRCUMFRANCE and go from thereFJ40Trevor said:
Why is this inaccurate? I think it would be more accurate to take into account the sidewall flex instead of the "ideal" diameter of the tire with no loads on it.
Either way, I agree with everyone else, 33" is close enough.
if you squish a circle into an elipse then mesure diagonloy thru the center you will allways get a diferent mesurement .
also keep in mind, new mud tires are generaly 1-2" taller than a bald tire....