How to Use a Dial Indicator to Determine the Lateral Deviation of Disc Brakes Rotors

What is the disc brake rotor lateral deviation?

The incorrect setup of disc brakes, caused by excessive wear and tear, mechanical overloads and contamination with dirt and rust, can cause the appearance of a warping of the rotor of the disc brakes, also known as an excessive lateral deviation. When this happens the driver will often feel an unusual vibration in the vehicle when the brake pedal is operated, especially at smaller speeds. Also, drivers can experience other problems such imprecise movement of the wheels and increased braking distance.

What is the correct setup of disc brake rotors?

Typically, a rotor should have a maximum lateral deviation of 50 micrometers. This means that the difference between the values of minimum and maximum lateral measurements should be 0.05 millimeters.

Use a Dial Indicator to Determine the Lateral Deviation of Disc Brakes

How to determine the run out of disc brake rotors?

A mechanic looking to inspect the lateral deviation of a rotor should follow the next steps:

  1. Put the vehicle in the Neutral shift.
  2. Remove the rotor, make sure that there is no dirt behind it and refit the lug nuts if they are loosen.
  3. Fix the rotor back on the wheel hub and tighten it securely.
  4. Fix the dial indicator on the brakes caliper.
  5. Position the dial indicator, so the plunger touches the surface of the rotor at roughly 1 centimeter from the exterior edge of the rotor.
  6. Move the dial indicator until the plunger is slightly preloaded and perpendicularly aligned on the surface of the rotor.
  7. Slowly spin the rotor clockwise.
  8. Watch the dial indicator and observe if the deviation of the needle in any direction is greater than the specifications (in our case 0,05 millimeters)
  9. If necessary refinish the motor and mount it back on the wheel hub.
  10. Repeat the above steps to make sure that the rotor lateral deviation is within the vehicle specifications.

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