1|Page
CDL - Air Brakes Exam Questions
100% Complete Solutions
After every working day - ✔✔Oil and water usually collect in compresed air tanks. If
you do not have an automatic tank drain, when should you drain the air tanks?
Why drain water from the compressed air tanks? - ✔✔Water can freeze in cold weather
and cause brake failure.
The air brake system for a straight truck or bus should not leak at a rate of more than
__________ psi per minute with the engine off and the brakes released. - ✔✔2
To make an emergency stop with air brakes, using the stab braking method, you
should: - ✔✔Press on the brake pedal as hard as you can, release the brakes when the
wheels locked, put on the brakes again when the wheels start rolling.
You should know that your brakes are fading when: - ✔✔You have to apply the brake
pedal harder to control speed on a downgrade.
If the air compressor should develop a leak, what keeps the air in the tanks? - ✔✔The
one way check valve.
To check the brake slack on S-cam brakes you should park on: - ✔✔Park on level
ground, chock the wheels, and release the parking brakes.
Author: Katelyn Whitman. ©2025, All Rights Reserved.
, 2|Page
The application pressure gauge shows how much pressure you have: - ✔✔When you
are applying to the brakes.
The spring brakes used on the chambers in a straight truck will bring you to a stop
when air pressure drops below ______ psi. - ✔✔20
The safety valve is set to automatically reduce pressure at ________ psi. - ✔✔150
Your truck has a dual air system and one system loses its pressure. What will happen? -
✔✔Either the front or back brake will not be fully operational.
If your truck or bus has dual parking control valves, you can use pressure from a
separate tank to: - ✔✔Release the spring emergency/parking brakes to move a short
distance.
If your truck has a properly functioning dual air brake system and minimum size air
tanks. The air pressure should build from 85 to 100 psi within _______ seconds? - ✔✔45
During normal driving, spring brakes are usually held back by: - ✔✔Air pressure
The air compressor stops pumping air at what psi? - ✔✔125
The driver must be able to see a warning before pressure in the service air tanks falls
below ________ psi. - ✔✔55
Excessive use of the service brakes results in overheating which can lead to: -
✔✔Expansion of the brake drums.
Author: Katelyn Whitman. ©2025, All Rights Reserved.
, 3|Page
The most common type of foundation brake found on heavy vehicles is the: - ✔✔S-cam
drum
If you must make an emergency stop, brake so you: - ✔✔Can steer and your vehicle
stays in a straight line.
The braking power of the spring brakes: - ✔✔Depends on the service brakes being in
adjustment.
The air brake lag distance at 55 mph on dry pavement adds about _______ feet. - ✔✔32
Total stopping distance for air brakes is longer than that for hydraulic brakes due to
_______ distance. - ✔✔Brake lag
It is accepted that too much heat caused by using your brakes too often can also cause: -
✔✔Brake fade or failure
Repeatedly pressing and releasing (fanning) the brake pedal may result in: - ✔✔The loss
of brake air pressure
The brake system that applies and releases the brakes when the driver uses the brake
pedal is the ________ brake system. - ✔✔Service
A slack adjuster's free play needs to be adjusted if it is more than about how many
inches when you pull hard on it? - ✔✔1 inch
Author: Katelyn Whitman. ©2025, All Rights Reserved.
CDL - Air Brakes Exam Questions
100% Complete Solutions
After every working day - ✔✔Oil and water usually collect in compresed air tanks. If
you do not have an automatic tank drain, when should you drain the air tanks?
Why drain water from the compressed air tanks? - ✔✔Water can freeze in cold weather
and cause brake failure.
The air brake system for a straight truck or bus should not leak at a rate of more than
__________ psi per minute with the engine off and the brakes released. - ✔✔2
To make an emergency stop with air brakes, using the stab braking method, you
should: - ✔✔Press on the brake pedal as hard as you can, release the brakes when the
wheels locked, put on the brakes again when the wheels start rolling.
You should know that your brakes are fading when: - ✔✔You have to apply the brake
pedal harder to control speed on a downgrade.
If the air compressor should develop a leak, what keeps the air in the tanks? - ✔✔The
one way check valve.
To check the brake slack on S-cam brakes you should park on: - ✔✔Park on level
ground, chock the wheels, and release the parking brakes.
Author: Katelyn Whitman. ©2025, All Rights Reserved.
, 2|Page
The application pressure gauge shows how much pressure you have: - ✔✔When you
are applying to the brakes.
The spring brakes used on the chambers in a straight truck will bring you to a stop
when air pressure drops below ______ psi. - ✔✔20
The safety valve is set to automatically reduce pressure at ________ psi. - ✔✔150
Your truck has a dual air system and one system loses its pressure. What will happen? -
✔✔Either the front or back brake will not be fully operational.
If your truck or bus has dual parking control valves, you can use pressure from a
separate tank to: - ✔✔Release the spring emergency/parking brakes to move a short
distance.
If your truck has a properly functioning dual air brake system and minimum size air
tanks. The air pressure should build from 85 to 100 psi within _______ seconds? - ✔✔45
During normal driving, spring brakes are usually held back by: - ✔✔Air pressure
The air compressor stops pumping air at what psi? - ✔✔125
The driver must be able to see a warning before pressure in the service air tanks falls
below ________ psi. - ✔✔55
Excessive use of the service brakes results in overheating which can lead to: -
✔✔Expansion of the brake drums.
Author: Katelyn Whitman. ©2025, All Rights Reserved.
, 3|Page
The most common type of foundation brake found on heavy vehicles is the: - ✔✔S-cam
drum
If you must make an emergency stop, brake so you: - ✔✔Can steer and your vehicle
stays in a straight line.
The braking power of the spring brakes: - ✔✔Depends on the service brakes being in
adjustment.
The air brake lag distance at 55 mph on dry pavement adds about _______ feet. - ✔✔32
Total stopping distance for air brakes is longer than that for hydraulic brakes due to
_______ distance. - ✔✔Brake lag
It is accepted that too much heat caused by using your brakes too often can also cause: -
✔✔Brake fade or failure
Repeatedly pressing and releasing (fanning) the brake pedal may result in: - ✔✔The loss
of brake air pressure
The brake system that applies and releases the brakes when the driver uses the brake
pedal is the ________ brake system. - ✔✔Service
A slack adjuster's free play needs to be adjusted if it is more than about how many
inches when you pull hard on it? - ✔✔1 inch
Author: Katelyn Whitman. ©2025, All Rights Reserved.
