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.

1. Raise and suitable support the vehicle. Refer to Lifting and Jacking the Vehicle .
2. Remove the tire and wheel assemblies.

•	For vehicles with steel wheels, refer to Tire and Wheel Removal and Installation in Tires and Wheels.

•	For Chevrolet and Oldsmobile vehicles with aluminum wheels, refer to Tire and Wheel Removal and Installation in Tires and Wheels.

•	For Pontiac vehicles with aluminum wheels, refer to Tire and Wheel Removal and Installation in Tires and Wheels.

Caution: One or more of the following guidelines may apply when performing specific required tests in the work stall:

•	When a test requires spinning the drive wheels with the vehicle jacked up, adhere to the following precautions:

-	Do not exceed 56 km/h (35 mph) when spinning one drive wheel with the other drive wheel stopped. This limit is necessary because the speedometer indicates only one-half the actual vehicle speed under these conditions. Personal injury may result from excessive wheel spinning.

-	If all of the drive wheels are spinning at the same speed, do not exceed 112 km/h (70 mph). Personal injury may result from excessive wheel spinning.

-	All persons should stay clear of the rotating components and the balance weight areas in order to avoid possible personal injury.

-	When running an engine in the repair stall for an extended period of time, use care not to overheat the engine and the transmission.

•	When a test requires jacking up the vehicle and running with the wheels and brake rotors removed, adhere to the following precautions:

-	Support the suspension at normal ride height.

-	Do not apply the brake with the brake rotors removed.

-	Do not place the transmission in PARK with the drive axles spinning.

-	Turn Off the ignition in order to stop the powertrain components from spinning.

•	When running an engine in the work stall, use the exhaust removal system to prevent breathing dangerous gases.

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:

5.1.	Remove the rotors/drums.

5.2.	Run the vehicle back to speed.

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

6.1.	Remove the rotors/drums one at a time.

6.2.	Perform the vibration test for each rotor/drum.

6.3.	Replace the rotor/drum that is causing the imbalance.

6.4.	Inspect the balance of the new rotor/drum.

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.