Practice question

When a brake pedal is pressed and the S-cam is turned, the S-cam:

  1. Presses the brake shoes against the inside of the brake drum.
  2. Tightens the brake drum onto the axle.
  3. Presses the brake lining against the wheel.
  4. Releases air from the air tanks.

Answer: A — Presses the brake shoes against the inside of the brake drum.

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Practice more: Pennsylvania CDL Air Brakes Test 2 →