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Inspecting Air Brakes — CDL Air Brakes Practice Test

Inspecting Air BrakesQuestion 1 of 30

30 questions in this topic · 30 drawn at random this round

How do you set up the static air leakage rate test?

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 Inspecting Air Brakes practice set has 30 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 Inspecting Air Brakes bank with the correct answer and an explanation. The practice quiz above draws 30 questions at random from the same bank.

  1. Compared with a vehicle without air brakes, how much do you need to inspect on a vehicle WITH air brakes?

    • More things — use the seven-step method plus extra air-brake checks — Correct answer
    • Fewer things, because air brakes are self-checking
    • Exactly the same things
    • Only the tires need checking

    Explanation: Use the same basic seven-step procedure, but there are MORE things to inspect on a vehicle with air brakes. English term: air brake system（气压制动系统 / sistema de frenos de aire）.

    Handbook: Inspecting Air Brakes — Seven-Step Procedure

  2. During the engine compartment check, what must you inspect on a belt-driven air compressor?

    • The condition and tightness of the drive belt — Correct answer
    • The color of the belt only
    • Nothing — a belt-driven compressor needs no check
    • The air pressure gauge reading

    Explanation: If the air compressor is belt-driven, check the condition and tightness of the drive belt — it should be in good condition. English term: air compressor（空气压缩机 / compresor de aire）.

    Handbook: Inspecting Air Brakes — Air Compressor Drive Belt

  3. Before checking the slack adjusters on S-cam brakes, what must you do first?

    • Park on level ground, chock the wheels, then release the parking brakes — Correct answer
    • Set the parking brakes hard and leave the engine running
    • Drive slowly while pulling the adjuster
    • Park on a steep hill so the brakes are loaded

    Explanation: Park on level ground, chock the wheels so the vehicle cannot move, then release the parking brakes so you can move the slack adjusters. English term: slack adjuster（间隙调整臂 / ajustador de holgura）.

    Handbook: Inspecting Air Brakes — Checking Slack Adjusters