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Air Brakes Practice Test 2

Last updated on May 5, 2023

Air Brakes Practice Test 2 contains knowledge and safe driving information that all commercial drivers should know to successfully pass the CDL “Air Brakes” written test.

Air Brakes Practice Test #2 Test Methods:

Number of practice test questions with answers: 25

Number of correctly answered practice test questions needed to pass: 20

Passing score: 80%

This CDL Air Brakes Practice Test #2 with Answers is applicable for all 50 States.

CDL Air Brakes Practice Test #1

CDL Air Brakes Practice Test #2 With Answers:



#1. Air supply pressure gauges tell you:

#2. When you apply the brakes as hard as you can without locking the wheels up, this is called:

#3. The time required for the air brakes to work (about a ½ second) after the brake pedal is pushed, is called:

#4. The safety valve installed in the first air tank the air compressor pumps air to, is set to open at:

#5. To check the rate of air pressure buildup on a commercial motor vehicle (CMV) equipped with a dual air brake system, the air pressure should build from 85 to 100 psi within ________ when the engine is at operating RPM.

#6. Brake drums (or discs) must not have cracks longer than ________ of the friction area.

#7. On a commercial motor vehicle (CMV) with a dual air brake system, what should the minimum air pressure be in both the primary and secondary systems before driving?

#8. On large buses, it is common for the low-pressure warning devices to signal at:

#9. The air compressor governor controls:

#10. The spring brakes will come on automatically when the air pressure drops into the range of _______.

#11. To come to a smooth, safe stop in a commercial motor vehicle (CMV) with a manual transmission, do not push the clutch in until the engine rpm is:

#12. You should never leave your vehicle unattended without applying the parking brakes or:

#13. All trucks, truck tractors, and buses must be equipped with __________ brakes and parking brakes.

#14. The air brake lag distance at 55 mph on dry pavement adds about _________ to the total stopping distance.

#15. The manual adjustment of an automatic slack adjuster to bring a brake push rod stoke within legal limits is:

#16. If a manual slack adjuster on an S-Cam brake moves more than _______ where the push rod attaches to it, it needs adjustment.

#17. To test the service brakes, wait for normal air pressure, release the parking brake, move the vehicle forward at about ______ mph, and apply the brakes firmly using the brake pedal.

#18. Some commercial motor vehicles (CMVs) are equipped with a low air pressure warning device that drops into the driver’s view; this device is called a:

#19. What is the maximum air leakage rate for a single vehicle?

#20. Excessive heat that causes chemical changes in the brake lining, resulting in the expansion of the brake drums and reduced friction is called:

#21. The _________ helps reduce the risk of ice in the air brake valves and other air brakes system parts during freezing weather.

#22. Antilock braking systems (ABS) do not _________ your stopping distance, but does help keep the vehicle under control during hard braking.

#23. Tests have shown that front wheel brakes are:

#24. Air tanks are equipped with a drain valve to remove:

#25. On newer commercial motor vehicles (CMVs), the knob labeled “parking brakes” is a:


CDL Air Brakes Practice Test #1


The pool of questions used to produce this practice test have been independently created by CDL Digest and come directly from Code of Federal Regulations (Title 49 – Transportation) and the information provided in AAMVA’s “2005 CDL Test System (July 2010 or newer Version) Model Commercial Driver Manual”.

These are the same sources that all 50 State Driver Licensing Agencies (SDLA) are required to use by federal regulation (49 C.F.R. 383.133) to develop the pool of questions for all written tests needed for a person to obtain a commercial learner’s permit (CLP), commercial driver’s license (CDL), and/or any federally authorized endorsements.

Note: The above listed source information is static, meaning changes to the information used to create the pool of questions that your State Driver Licensing Agency (SDLA) uses for the actual written test have been extremely rare over the decades. Due to the static nature of the source information, you may see practice test questions and answers in this practice test that are very similar, if not identical to the questions and answers on the actual written test. If this occurs, it is purely coincidental. CDL Digest is not affiliated with the AAMVA or any government agency.


The source material used by CDL Digest to develop these practice test questions is very technical. Relying solely on the practice tests we have produced will not be enough to successfully pass the actual written tests. You will NEED to study in order to successfully pass these practice tests and the actual written tests.

Class “A” Commercial Learner’s Permit Study Guide

Class “B” Commercial Learner’s Permit Study Guide

Complete CDL Study Guide

CDL Air Brakes Study Guide

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