Why Do I Feel a Pulsation When Applying My Brakes?

Why Do Your Brakes Pulsate?

Most of us have experienced it…you’re driving and apply the brakes, only to feel a wobbly pulsation feeling coming through the brake pedal.  Typically, this is the result of a warped brake rotor (rotor is not perfectly flat and parallel with the plane rotation).

An on-vehicle brake lathe is an ideal tool to resolve a brake pulsation related to a warped rotor.  The lathes, or rotor matching systems, are considered without equal by many major automotive manufacturers for their accuracy and ease of use.

Three results to expect when having your rotors machined at Ottawa Dodge:

  • Elimination of lateral run-out (LRO) as measured on the outer pad mating surface of the rotor to less than .002″ (matching the rotor to the vehicle’s hub).
  • A flat (no thickness variation), smooth, clean surface finish with a roughness average of between 30 and 60 micro inches.  This will match the rotor to the brake pads and ensure full, even contact for best stopping power.
  • Leaving the rotor above the thickness specification.

Three results to expect when having your rotors machined at Ottawa Dodge:

  • Lateral run-out greater than .002″ is, over time, the root cause of thickness variation, which is the direct cause of brake pedal pulsation.
  • A rough surface finish will cause brake noise and potentially affect stopping distances.
  • It is possible to believe the problem is fixed if there is no pedal pulsation after the work is completed.  Pedal pulsation may not develop until after 8kms.

Thickness Variation is generally a result of excess lateral run-out (wobble) causing the rotor to scuff the brake pads on the “high spot” once each revolution. Today’s aggressive semi-metallic pad materials wear away the surface of the rotor at this high spot over time (usually after 8,000kms) until the thickness variation is great enough to be felt in the brake pedal as pulsation.

Lateral Run-Out (LRO) is the amount of “wobble” in the rotor or side-to-side movement as the brake rotor completes one revolution. 


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