Oregon CDL Air Brake Test (OR) 2026

4.9 out of 5 (74 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Preparing for your Oregon commercial driver's license (CDL) air brakes endorsement doesn't have to be stressful. The Oregon CDL air brake practice test on our website is designed to offer a comprehensive learning experience in a relaxed environment. With a set of 20 carefully curated multiple-choice questions, this Oregon DMV practice test covers everything you need to know about air brake systems. This includes detailed explorations of crucial components like compressors, reservoirs, and brake chambers, as well as insights into operational principles and safety protocols. One key aspect of the Oregon DMV air brake test is its focus on the unique brake lag time found in air brake systems. Understanding this delay is essential for calculating stopping distances accurately, which is crucial for safe driving. By mastering this and other topics, you'll be well-prepared to meet the requirements for the air brakes endorsement on your CDL. Unlike the official DMV test, our Oregon driver's permit practice test is not timed, allowing you to take your time with each question. This no-pressure setting lets you learn at your own pace, absorbing the material without the stress of a ticking clock. After completing the Oregon CDL air brakes practice test, you can review your answers, check any hints and explanations for questions you missed, and gain a clearer understanding of the material. Achieving a passing score requires correctly answering at least 16 out of 20 questions. This ensures you have a solid grasp of the air brakes' fundamentals and are ready for the actual endorsement test. The Oregon CDL air brake practice test is an excellent resource for building confidence and knowledge in a supportive environment. It provides you with the tools you need to excel in your air brakes CDL test and become a safer, more knowledgeable commercial driver. Dive into this valuable practice opportunity today and take the next step toward your commercial driving career.
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Sample Oregon Air Brakes Test Questions

Question 1

What should you do when the low-air-pressure warning activates while driving?

  1. A. Bring the vehicle to a safe stop and park as soon as possible
  2. B. Shift into a higher gear
  3. C. Make a sudden full brake application
  4. D. Open the air-supply valve

Correct answer: A. – Bring the vehicle to a safe stop and park as soon as possible

The Oregon manual directs the driver to stop and safely park as soon as possible when the warning activates. Low pressure may indicate an air leak, and only limited controlled braking remains before the spring brakes apply. Waiting for automatic spring-brake application can cause a lightly loaded vehicle to skid or leave a heavily loaded vehicle with a long stopping distance.

Source: Oregon Commercial Driver License Manual — § 5.4.7, “Low Air Pressure”

Question 2

How should you test the low-air-pressure warning signal?

  1. A. Shut off the engine, turn on electrical power, and repeatedly press and release the brake pedal
  2. B. Pull on each slack adjuster while the vehicle is moving
  3. C. Release the parking brake and accelerate rapidly
  4. D. Make a hard stop at more than 20 mph

Correct answer: A. – Shut off the engine, turn on electrical power, and repeatedly press and release the brake pedal

Begin with enough pressure that the warning is off, shut down the engine, and turn on the electrical power. Press and release the brake pedal to reduce tank pressure. The warning must activate before pressure falls below 55 psi in the tank, or in the lowest-pressure tank of a dual system.

Source: Oregon Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 3

Why must moisture be drained from compressed-air tanks?

  1. A. It causes the compressor to become too cold
  2. B. Its low boiling point reduces brake pressure
  3. C. It can freeze and interfere with brake operation
  4. D. It increases the compressor’s oil level

Correct answer: C. – It can freeze and interfere with brake operation

Water and compressor oil collect in the bottom of air tanks. In cold weather, the water can freeze and contribute to brake failure by interfering with air-system operation. Tanks with manual drain valves must be drained completely at the end of each driving day; automatic drains expel the collected material automatically.

Source: Oregon Commercial Driver License Manual — § 5.1.4, “Air Tank Drains”

Question 4

During an applied air-leakage test, the maximum allowed pressure drop for a combination vehicle is 1 psi in one minute.

  1. A. True
  2. B. False

Correct answer: B. – False

The Oregon manual sets the applied leakage-test limit at 4 psi in one minute for a combination vehicle. For a single vehicle, the limit is 3 psi in one minute. If the pressure drops faster than the applicable limit while the service brake is fully applied, the leak must be found and repaired before driving.

Source: Oregon Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 5

What function does the brake pedal perform in an air-brake system?

  1. A. It mechanically pulls the slack adjusters with connecting rods
  2. B. It controls the air pressure applied to the brakes
  3. C. It serves as a footrest when the vehicle is moving
  4. D. It directly turns the brake camshaft

Correct answer: B. – It controls the air pressure applied to the brakes

The brake pedal is also called the foot valve or treadle valve. Pressing it harder applies more air pressure to the brakes, while releasing it reduces pressure and releases the brakes. Unnecessary pedal applications use stored air faster and can reduce tank pressure faster than the compressor replaces it.

Source: Oregon Commercial Driver License Manual — § 5.1.7, “The Brake Pedal”

Question 6

Brake fade can occur only in vehicles equipped with drum brakes.

  1. A. True
  2. B. False

Correct answer: B. – False

The Oregon manual explains that brake shoes or pads press against drums or discs to slow the vehicle, producing heat. Excessive service-brake use can create enough heat for braking effectiveness to fade or fail. Brake adjustment also matters because out-of-adjustment brakes make the remaining brakes work harder and overheat.

Source: Oregon Commercial Driver License Manual — § 5.4.5, “Brake Fading or Failure”

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