Brake Systems Flashcards

What is the most common cause of pedal pulsation on a vehicle with disc brakes?

Answer: Rotor thickness variation (lack of parallelism)

Thickness variation makes the caliper piston move in and out as the rotor turns, and the driver feels that as pedal pulsation.

What does the 'MIN THK' dimension cast into a brake rotor mean?

Answer: The thickness at which the rotor must be discarded

MIN THK is the discard thickness, and a rotor at or below it must be replaced.

What retracts the disc brake caliper piston slightly after the brakes are released?

Answer: Deflection of the square-cut piston seal

The square-cut seal twists when the piston applies and then pulls the piston back a small amount when pressure is released.

When replacing pads on a rear disc caliper with an integral parking brake, how is the piston usually retracted?

Answer: By rotating it inward with a special tool

Integral parking brake calipers use a screw mechanism, so the piston has to be turned while it's pushed back in.

A vehicle pulls to the left only when braking. Which condition could cause this?

Answer: A seized caliper piston on the right front

If the right front caliper can't apply fully, the left front does more of the braking and the vehicle pulls left.

Which procedure helps prevent rotor distortion when wheels are reinstalled?

Answer: Torquing the lug nuts to specification in a star pattern

Torquing in a star pattern to specification clamps the rotor hat evenly and helps prevent lateral runout and thickness variation.

Which tool is used to measure rotor lateral runout?

Answer: Dial indicator

A dial indicator mounted against the rotor face measures side-to-side wobble while the rotor turns.