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Free Air Brakes CDL Practice Test

Use this free Air Brakes commercial drivers license practice test to prepare yourself to get your CLP (commercial learner's permit). To learn more about Roehl's paid CDL training, view our Get Your CDL page or apply now.

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Question 1 of 30

What is the best way to test if your vehicle's spring brakes come on automatically?


Question 2 of 30

Which of the following factors can cause brakes to fail or fade?


Question 3 of 30

When should you drain your air tanks?


Question 4 of 30

Which of the following should you do before leaving your vehicle unattended?


Question 5 of 30

How would you check your truck's slack adjusters?


Question 6 of 30

Which of the following is true about your brake function if your ABS fails?


Question 7 of 30

Slack adjusters are:


Question 8 of 30

How do brakes work on a long, steep downgrade?


Question 9 of 30

Spring brakes are:


Question 10 of 30

If the brakes are wet, what can be done to dry them out?


Question 11 of 30

What should you never do when the spring brakes are on?


Question 12 of 30

Most heavy-duty vehicles have a dual air brake system. What is a dual air brake system?


Question 13 of 30

Before driving a vehicle with a dual air system, the driver must allow what to happen?


Question 14 of 30

Which of the following is true about a dual air brake system?


Question 15 of 30

What is the correct way to slow a large vehicle down on long downgrades?


Question 16 of 30

Pressing on the brakes as hard as you can, releasing when they lock up, then pressing the brakes fully again when the wheels are rolling is called what?


Question 17 of 30

In a dual air brake system, which parts of braking does each system typically operate?


Question 18 of 30

With air brakes, there is an added delay when stopping. What causes this?


Question 19 of 30

Where is compressed air stored?


Question 20 of 30

To test the air leakage rate, one must turn off the engine (with a fully charged air system), turn the key to the on position, release the service brake, and do what?


Question 21 of 30

Chemical changes in the brake lining, which reduce friction and cause expansion on the brake drums is known as what?


Question 22 of 30

Which of the following is a reason that air tanks must be drained?


Question 23 of 30

Why is it especially important to have your brakes adjusted before going down steep grades?


Question 24 of 30

In what instances should you not use the parking brakes when parking?


Question 25 of 30

If parking brakes are not being used when the vehicle is parked, what must be done instead?


Question 26 of 30

Which device allows you to remove oil and water from the air brake systems?


Question 27 of 30

What does it mean when the safety valve opens and releases air?


Question 28 of 30

If you press and release the brake pedal rapidly, what will happen?


Question 29 of 30

Which device helps reduce the risk of ice in the air brake systems during cold weather?


Question 30 of 30

What is modulating control valve?


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