Calculating Tire Rotation

Tire/Wheel And Propshaft Rotation:

Determine the rotational speed of the tires in revolutions per second, or Hertz (Hz), based on the vehicle speed at which the vibration occurs. In order to determine the rotational speed, use the following procedure:
1. Determine the speed at which the vibration occurs.
2. Determine the number of 8 km/h (5 mph) increments:
- Divide the complaint speed by 8 when using kilometers.
- Divide the complaint speed by 5 when using miles.
3. Determine the vehicle tire size.
4. Locate on the table below, the Hertz value at 8 km/h (5 mph) for that tire size.
5. Multiply the Hertz value by the number of 8 km/h (5 mph) increments.
6. The result is the rotational speed of the tires in Hertz at the complaint speed. If this figure matches the vibration frequency, a first-order vibration is present in the tire and wheel assembly.
For example, if the complaint speed is 60 mph, the number of increments is 12. According to the following table, a tire with size of P235/75R15 has a value of 1.00 Hz. You can calculate the rotational speed at 60 mph:

12 increments x 1 Hz = 12 Hz

Tire/Speed Table:

Tire/Speed Table
Sometimes, the tire/wheel vibration may be of a higher-order. To compute possible higher-order vibrations, multiply the rotational speed of the tires in Hertz at the complaint speed by the order number If any of these matches the vibration frequency, then a vibration of that particular order is present in one (1) of the tire and wheel assemblies.