Rotor/Drum Imbalance

Rotor/Drum Imbalance

Rotors and drums do not have a set tolerance. However, rotors or drums with more than 21 g (0.75 ounce) imbalance have the potential to cause vibration. Inspect the rotors and the drums for imbalance using either the on-vehicle or the off-vehicle method.


Checking Rotor/Drum Imbalance (On-Vehicle)

1. Support the vehicle rear axle on a suitable hoist. Refer to Lifting and Jacking the Vehicle.
2. Remove the rear tire and wheel assemblies. Refer to Tire and Wheel Removal and Installation.
Caution: Refer to Work Stall Test Caution in Cautions and Notices.
3. Reinstall the wheel nuts in order to retain the rotors/drums.
4. Run the vehicle at the complaint speed while inspecting for the vibration.
5. If the vibration still exists, perform the following steps:

1. Remove the rotors/drums.
2. Run the vehicle back to speed.

6. If the vibration is eliminated, perform the following steps:

1. Remove the rotors/drums one at a time.
2. Perform the vibration test for each rotor/drum.
3. Replace the rotor/drum that is causing the imbalance.
4. Inspect the balance of the new rotor/drum.




Checking Rotor/Drum Imbalance (Off-Vehicle)

1. Measure the diameter and the width of the rotor/drum.




2. Mount the rotor/drum on a balancer in the same manner as a wheel.

Important: You can only inspect the rotors/drums for static imbalance. Ignore the dynamic imbalance reading.


3. Inspect for static imbalance.
4. If the rotor/drum shows imbalance, replace the rotor/drum.
5. Inspect the balance of the new rotor/drum before you install the rotor/drum on the vehicle.