T.winegar wrote:so like this: 285/235= 1.21
then
x miles= actual miles
Only if you drive on the sides of your tires.
285 is the width of the tire in millimeters. 285 millimeters is approximately 11.2 inches. The theoretical height of the tire is is 32.8 inches. That comes from this formula: 2 x width of tire x aspect ratio / 2540 + rim diameter = height of tire in inches. So, to figure the advertised height of a metric sized tire in inches, it would look like this: 2 x 285 x 75 /2540 + 16 = 32.8 inches. The height that the truck sees is the distance from the ground to the center of the axle x 2. That number will be less than the advertised size due to a number of factors, but mainly due to there being a load on the tire and the manufacturers measuring the tires unloaded.
A 285/75R16 works out to be about 32.8 inches tall from the formula and a 235/85R16 is about 31.5 inches. Thus, 32.8/31.5=1.0413 x indicated miles = actual miles.
