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Brake Rotor Runout Measurement

Lateral runout — side-to-side wobble of the installed rotor — is measured with a dial indicator against the friction surface while rotating the rotor; more than about 0.05 mm wears the rotor unevenly and eventually causes pedal pulsation. Excess runout is often the hub face or rust between hub and hat, so re-index the rotor and clean the hub before condemning parts.