Tennessee CDL Air Brake Test (TN) 2026

5 out of 5 (30 votes)
80% Passing score
20 Questions
4 Mistakes allowed
As a Tennessean looking to ace your commercial driver's license (CDL) air brakes endorsement, you're in the right place. Our Tennessee CDL air brake test offers a thorough selection of 20 multiple-choice questions designed to prepare you for the real test. This permit practice test delves into all critical aspects of air brake systems, from understanding the workings of compressors, reservoirs, and brake chambers to mastering operational principles and safety protocols. A unique feature of air brakes is their brake lag time, and this TN DMV permit test practice includes questions specifically addressing this aspect. Knowing how to calculate stopping distances considering brake lag is crucial for your safety and the safety of others on the road. To pass this Tennessee CDL air brake test, you'll need to correctly answer at least 16 questions, ensuring you're well-prepared and confident in your knowledge of air brake systems. Our TN DMV practice test is conveniently accessible online through mobile, desktop, and mobile apps, making it easy for you to study whenever and wherever you are. This Tennessee CDL air brake practice test is tailored to cover only the questions that appear on the actual CDL permit test for this endorsement. Remember, to obtain your commercial driver's license, you'll also need to pass the general knowledge test. If you need help with that, we offer comprehensive general knowledge prep tests as well. In addition to the TN DMV air brake test, we recommend supplementing your studies with the Tennessee Driver's Handbook, a state-certified driver's ed course, flashcards, and road sign charts. These resources will provide a well-rounded preparation, ensuring you're ready to tackle all areas of the DMV permit test. Taking our CDL air brakes practice test is an essential step towards earning your air brakes endorsement and ensuring you're fully equipped for safe and effective air brake operation.
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Sample Tennessee Air Brakes Test Questions

Question 1

Which condition can indicate that air brakes are fading on a downgrade?

  1. A. Less application pressure is required to maintain the same speed
  2. B. The brake pedal feels spongy when first pressed
  3. C. Increasing application pressure is needed to maintain the same speed
  4. D. The vehicle accelerates after the brake pedal is released

Correct answer: C. – Increasing application pressure is needed to maintain the same speed

Needing progressively greater application pressure to maintain the same speed indicates possible brake fade. The driver should slow down and use a lower gear. Increased pressure requirements can also result from brakes that are out of adjustment, air leaks, or other mechanical problems, so the condition requires prompt attention.

Source: Tennessee Commercial Driver’s License Manual — § 5.1.10, “Application Pressure Gauge”

Question 2

With the engine off and brakes released, pressure loss in a combination vehicle should be less than how many psi in one minute?

  1. A. 4 psi
  2. B. 3 psi
  3. C. 2 psi
  4. D. 1 psi

Correct answer: B. – 3 psi

In the Tennessee CDL inspection procedure, begin with a fully charged air system, turn off the engine, release the parking brakes, and time the pressure drop without applying the service brakes. A combination vehicle should lose less than 3 psi in one minute. A loss of 3 psi or more does not meet this test standard.

Source: Tennessee Commercial Driver’s License Manual — § 5.3.3, “Test Air Leakage Rate”

Question 3

What should you do first if 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 to a higher gear
  3. C. Make an immediate full-force 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

When the low-air-pressure warning activates, stop and safely park the vehicle as soon as possible. Do not continue until the spring brakes apply automatically because vehicle control may be lost as pressure continues to fall. The air-brake system must be repaired before the vehicle is driven again.

Source: Tennessee Commercial Driver’s License Manual — § 5.1.14, “Spring Brakes”

Question 4

How should the low-air-pressure warning signal be tested?

  1. A. Park safely, shut off the engine, turn on electrical power, and repeatedly press and release the brake pedal
  2. B. Push inward on each slack adjuster
  3. C. Release the parking brake and pull on each slack adjuster
  4. D. Drive above 20 mph and make a full emergency stop

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

The Tennessee CDL manual instructs the driver to shut off the engine with sufficient air pressure, turn on the electrical power, and repeatedly press and release the brake pedal. This reduces tank pressure in a controlled manner. The warning signal must activate before pressure falls below 55 psi in the tank with the lowest pressure.

Source: Tennessee Commercial Driver’s License Manual — § 5.3.3, “Test Low Pressure Warning Signal”

Question 5

If the low-air-pressure warning activates while driving, you should stop and safely park as soon as possible.

  1. A. TRUE
  2. B. FALSE

Correct answer: A. – TRUE

The statement is true. A low-pressure warning indicates that the air-brake system may no longer have adequate pressure for normal operation. Stop and safely park while the service brakes can still be controlled, rather than continuing until spring brakes begin applying automatically.

Source: Tennessee Commercial Driver’s License Manual — § 5.1.14, “Spring Brakes”

Question 6

A reachable slack adjuster on an S-cam brake that moves more than about one inch where the push rod attaches probably needs adjustment.

  1. A. TRUE
  2. B. FALSE

Correct answer: A. – TRUE

The statement is true. With the vehicle on level ground, wheels chocked, and parking brakes released, pull firmly on each reachable slack adjuster while wearing gloves. Movement greater than about one inch at the push-rod attachment indicates probable excessive slack; automatic slack adjusters should be professionally inspected because routine manual adjustment can mask a mechanical problem.

Source: Tennessee Commercial Driver’s License Manual — § 5.3.2, “Check Slack Adjusters on S-cam Brakes”, Tennessee Commercial Driver’s License Manual — § 5.3.2, “Manual Adjustment of Slack Adjusters”

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