Tire revolution per mile, which is the number of turns your tire makes per mile of distance travelled by the tire.

This factor alone will change the way in which your vehicle runs.

The smaller your tire, the faster the acceleration but your fuel economy will suffer or… The bigger the tire, the slower the acceleration but your fuel economy will improve.

This is because the axle ratio is changed once you deviate from the original size. So if you are thinking of changing your tire size and see the new axle ratio, here is the formula:

new tire rev/mile multiplied by original axle ratio divided by original tire rev/mile equals new axle ratio

Example:

1995 GM truck with original tire specs:

Old tire specs:

P245/75R15 tires with 690 revolution/mile

New tire specs:

32x10.50R15LT tires with 733 revolution/mile

The original axle ratio is 3.73

Using the formula above, we have:

(690 x 3.73) divided by 733 = 3.51 Effective Axle ratio (new axle ratio)

This new axle ratio is lower than the original one and will result in slower acceleration but will improve fuel economy.

Note:

To get actual tire rev/mile, divide one mile in feet by the tire's circumference in feet.