Aspect Ratio Calculator
To calculate aspect ratio, divide the tire's section height by its section width as shown below.
Section Height / Section Width = Aspect Ratio
Determine the aspect ratio of a P255/50VR16 tire.
This example indicates an approximate 50-series tire when mounted on its measuring rim width.
For wider-than-design measuring rim width wheel
When this same tire is mounted on a wider-than-design rim width wheel, the specifications can change dramatically. The tire's section width increases by 0.2" for every 0.5" increase in rim width. The difference between a 7.0" and a 9.5" wide wheel measures 2.5". The width difference of 2.5" equals five increments of 0.5".
For the increase in section width, multiply 0.2" by the corresponding five increments for a total of 1.0." Adding that to the original section width results in a new measurement of approximately 11.2".
Because the overall diameter of a radial is determined by its belts, this tire's overall diameter should remain virtually unchanged. To calculate the new aspect ratio we repeat the earlier calculation, this time substituting the revised section width of 11.2."