Tech Tip: Brake Vibration Diagnostics on Subaru Models – UnderhoodService
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Tech Tip: Brake Vibration Diagnostics on Subaru Models

Studies confirm that rarely is it necessary to resurface brake rotors and/or drums on all four wheels when a confirmed brake vibration exists. With proper diagnostics, front or rear brake vibrations can be isolated, eliminating the need to resurface all four rotors and/or rear brake drums.

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Applicability: All models, all years

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Studies confirm that rarely is it necessary to resurface brake rotors and/or drums on all four wheels when a confirmed brake vibration exists. With proper diagnostics, front or rear brake vibrations can be isolated, eliminating the need to resurface all four rotors and/or rear brake drums.

Repair Procedure:

Use the following procedure to conduct brake diagnostics.
Road-test the vehicle to confirm a brake vibration. If the vibration is felt when braking, verify at what speed it occurs.

Typically, front rotor vibration is felt at higher speeds (above 50 mph) and in the steering wheel (circumference direction and/or side to side). If this is the case, the front rotors and pads will need to be inspected.

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Typically, rear brake vibration is felt at lower speeds (below 50 mph). Vibration will also be felt in the floor of the vehicle, pedal, seats and dash. If this is the case, the rear rotors and pads will need to be inspected.

To check for rear drum vibration, road-test the ­vehicle at lower speeds. Be extremely careful not to lock the rear brakes. With the parking brake release button pushed in, pull the parking brake lever slowly and gently, which applies the rear parking brakes. If vibration is felt, the rear drums and shoes will need to be ­inspected.

Always refer to the applicable service manual for brake, brake drum and rotor specifications. When resurfacing, always check rotor/drum thickness ­before and after. These measurements must be noted on the repair order. If the rotor/drum is out of specification after resurfacing, it will need to be replaced.

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Diagnostics:
Whenever diagnosing for vibration, the first items that should be checked are: worn and/or loose suspension components, axles, tire pressure and conditions of tires, and check that all tires are of the correct/same size. In some cases, out of balance tires can also cause vibration. Always refer to the applicable service manual for vehicle specifications.

Courtesy of Mitchell 1.

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