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CDL Air Brakes Endorsement practice test

This free CDL air brakes endorsement practice test covers the knowledge test you take on top of your CDL, with original questions written from the federal knowledge requirements in 49 CFR Part 383.

  • Multiple-choice knowledge test
  • 80% to pass (49 CFR 383.135)
  • item count set by your state
Start 20 free questions What’s inside
  • No signup to start
  • Every answer includes a source note
  • Updated October 22, 2026

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Driving & Licenses · Exam prep

CDL Air Brakes Endorsement practice test: how the exam works and how to prepare

Original practice questions on the air brakes endorsement, written from the federal knowledge requirements in 49 CFR Part 383 and the public CDL manual facts; not official state test questions. The real CDL Air Brakes Endorsement test at a glance: Multiple-choice knowledge test, 80% to pass (49 CFR 383.135), item count set by your state. Use these free CDL Air Brakes Endorsement practice questions to learn the format and read the explanation and source note behind every answer.

80% is the federal threshold in 49 CFR 383.135. The regulation sets the percentage only — your state driver licensing agency sets how many questions the test has.

  • Learn the air brakes topics in the order your state manual teaches them
  • Use the free 20 first, then work the full bank by topic and retest what you missed
  • Read every explanation, including why the wrong options fail
  • Check your state's CDL manual for local numbers and rules before test day
Official format

The real test at a glance

What it takes to pass the CDL Air Brakes Endorsement test

80% to pass · question count set by your state

Quick Summary: The official CDL Air Brakes Endorsement knowledge test requires a minimum passing score of 80%. Format: Multiple-choice knowledge test. Sourced directly from official state testing blueprints.
  • Multiple-choice knowledge test
  • 80% to pass (49 CFR 383.135)
  • item count set by your state

80% is the federal threshold in 49 CFR 383.135. The regulation sets the percentage only — your state driver licensing agency sets how many questions the test has.

100
practice questions
20
free, no signup
80%
published threshold
50
questions per simulation

Topic coverage

Topics covered in this bank

100 original questions mapped to the listed source topics. Bars show how many questions each topic gets.

Original practice questions on the air brakes endorsement, written from the federal knowledge requirements in 49 CFR Part 383 and the public CDL manual facts; not official state test questions.

View full topic blueprint & drills →

Drill down by official testing module:

Inspection leak tests16System parts14Compressor governor tanks12Dual brakes spring12Stopping distance12Brake fade use12

From the question bank

Try 3 more real questions

Answer in your head, then check. Every explanation cites the official source.

  1. Q1System parts

    An air brake system on a heavy vehicle actually combines which three braking systems?

    1. AHydraulic, mechanical and electric braking
    2. BService, parking and emergency braking
    3. CPrimary, secondary and trailer-only braking
    4. DFoot, hand and engine-exhaust braking
    Show answer

    B. Service, parking and emergency braking Air brakes are described as three systems working together: service brakes slow the moving vehicle, parking brakes hold it stopped, and emergency brakes use parts of both to stop it after a failure. Treating them as one system hides the separate controls and air paths you must inspect.

  2. Q2Compressor governor tanks

    What does the air compressor governor do when tank pressure reaches the cut-out level?

    1. AIt opens the safety valve to release excess air
    2. BIt drains water from the bottom of each tank
    3. CIt stops the compressor from pumping more air
    4. DIt sends extra air to the trailer brake line
    Show answer

    C. It stops the compressor from pumping more air At the cut-out point, roughly 125 psi, the governor halts compressor output so the tanks do not keep rising. When pressure later falls to the cut-in point, about 100 psi, it lets the compressor pump again. Opening the safety valve is a separate protection that works only if the pressure keeps climbing past the governor's setting, and draining the tanks is a manual job done at the end of the day.

  3. Q3Dual brakes spring

    A dual air brake system uses two separate air systems that share what?

    1. AOne common set of air tanks
    2. BThe same supply line to the trailer
    3. CA single set of brake controls
    4. DOne drain valve serving both circuits
    Show answer

    C. A single set of brake controls The two circuits have their own tanks, hoses and lines, but the driver works them through one set of brake controls. That separation is what lets one circuit keep braking when the other loses pressure. The tanks, hoses and lines are not shared, which is why choosing 'one common set of tanks' or a shared drain would defeat the purpose of having two circuits.

All 20 free questions with answers Take them as a timed quiz

Study plan

How to pass the CDL Air Brakes Endorsement

The order that works: learn the rules, drill until they’re automatic, then use the exam simulator to check consistency.

  1. 1

    Learn the air brakes topics in the order your state manual teaches them

  2. 2

    Use the free 20 first, then work the full bank by topic and retest what you missed

  3. 3

    Read every explanation, including why the wrong options fail

  4. 4

    Check your state's CDL manual for local numbers and rules before test day

Exam simulator

Sit a timed mock test for the Air Brakes

One question at a time against a real countdown, no feedback until you submit, flag questions to come back to, then a score against the pass mark with a by-topic breakdown and every answer explained. Topics are mixed across the whole bank, and a retake is a new draw.

Try the free mock test

The free mock test runs 20 questions from the free set, once. Unlocking adds full-length runs of 50 questions from the whole bank. A practice mock test, not an official replica.

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20 q
Full run
50 q
Practice clock
50 min
Pass mark
80%

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  • All 100 questions, every topic
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80% is the federal threshold in 49 CFR 383.135. The regulation sets the percentage only — your state driver licensing agency sets how many questions the test has.

Free study kit

Everything free for the CDL Air Brakes Endorsement test

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About these questions

Written by QuizCram from the official source and verified against its text — never copied from a real exam. Original practice questions on the air brakes endorsement, written from the federal knowledge requirements in 49 CFR Part 383 and the public CDL manual facts; not official state test questions.

Questions last updated
October 22, 2026
Bank version
v1 · 100 questions

Good to know

CDL Air Brakes Endorsement FAQ

Federal rules set the 80% passing threshold but not a question count. Each state writes its own test, so confirm the number with your state agency.

No. These are original practice questions on the air brakes endorsement. Your state licensing agency writes and scores the real test, and its CDL manual is the final word on local rules.

Yes. Open the exam simulator and sit a timed mock test of 20 questions built from the free questions, once, with no signup. Unlocking the exam adds full-length runs of 50 questions in 50 minutes (a practice clock), as many as you like, each a new draw from the whole bank.

The exam's agency publishes no topic weights, so it mixes topics in proportion to the question bank, favouring questions you missed before and never repeating one within a run. A retake is a new draw, so you will meet different questions. It is a practice mock test, not an official replica of the real exam.

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