Practice question

On the Michigan CDL Air Brakes test, why is heat the enemy of brake drums on long downgrades?

  1. Heat improves friction
  2. Heat causes drums to expand away from the linings (fade) and can crack the drums or burn the linings
  3. Heat freezes the air
  4. Heat strengthens metal

Answer: B — Heat causes drums to expand away from the linings (fade) and can crack the drums or burn the linings

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