Calculating Overall Tire Diameter

Penske Truck Rental offers two devices for towing your vehicle, a tow dolly and a car carrier. The formula below will help you determine which device you will need to use based on your towed vehicle's tire size.

tire illustration showing info

The tire size can be found on the side wall of your tire.

Use the formula below to determine your overall tire diameter.

(Cross Section Width * (Aspect Ratio / 100)) * 2 + Wheel Diameter
25.4

For example, if the tire size is 225/50R 16, the equation will be implemented as follows:

(225 * (50 / 100)) * 2 + 16 = 24.85
25.4

Which Towing Device Do I Need?

  • A tow dolly is required when the overall tire diameter limitation is 22 to 27 inches.
  • A car carrier is required when the overall tire diameter limitation is 22 to 28 inches.