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Downhill Braking & Brake Fade — CDL Air Brakes Practice Test

Downhill Braking & Brake FadeQuestion 1 of 16

16 questions in this topic · 16 drawn at random this round

Using the proper downhill braking technique, when should you release the brakes?

CDL Manual — Air Brakes

Questions are based on the official CDL manual (AAMVA model) used by state DMVs. The real CDL knowledge test is given in English — federal rules (FMCSA, 49 CFR 391.11) require English proficiency to drive commercially; our Chinese & Spanish are study aids. Some states also offer the written test in other languages (see the per-state table).

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This CDL Air Brakes Downhill Braking & Brake Fade practice set has 16 practice questions based on the official exam materials, each with an instant explanation. You need 80% on the real CDL Air Brakes knowledge test to pass.

Sample questions

Three questions from the Downhill Braking & Brake Fade bank with the correct answer and an explanation. The practice quiz above draws 16 questions at random from the same bank.

  1. On a long, steep downgrade, the use of the brakes is only a supplement to what?

    • The braking effect of the engine — Correct answer
    • The parking brake
    • The spring brakes
    • The trailer hand valve

    Explanation: On a long and/or steep downgrade, the use of the brakes is only a supplement to the braking effect of the engine; engine braking should be the primary way you control your speed downhill. English term: engine brake（发动机制动 / freno de motor）.

    Handbook: Downhill Braking & Brake Fade — Engine Braking First

  2. What causes brakes to fade or fail on a downgrade?

    • Excessive heat from using them too much instead of engine braking — Correct answer
    • Too much air pressure in the brake chambers
    • Driving in too low a gear down the hill
    • Cold weather freezing the brake linings

    Explanation: Brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect. English term: brake fade（制动衰退 / pérdida de frenado）.

    Handbook: Downhill Braking & Brake Fade — What Causes Fade

  3. What does excessive use of the service brakes lead to?

    • Overheating and brake fade — Correct answer
    • Better, longer-lasting brakes
    • Lower air tank pressure that never recovers
    • Faster cut-out of the governor

    Explanation: Excessive use of the service brakes results in overheating and leads to brake fade. English terms: service brake（行车制动 / freno de servicio）, brake fade（制动衰退 / pérdida de frenado）.

    Handbook: Downhill Braking & Brake Fade — Overheating