CDL - Air Brakes Exam 2025 Questions
and Answers
After every working day - --CORRECT ANSWER--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? - --CORRECT ANSWER--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. - --
CORRECT ANSWER--2
To make an emergency stop with air brakes, using the stab braking method, you
should: - --CORRECT ANSWER--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: - --CORRECT ANSWER--
You have to apply the brake pedal harder to control speed on a downgrade.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
,If the air compressor should develop a leak, what keeps the air in the tanks? - --
CORRECT ANSWER--The one way check valve.
To check the brake slack on S-cam brakes you should park on: - --CORRECT
ANSWER--Park on level ground, chock the wheels, and release the parking brakes.
The application pressure gauge shows how much pressure you have: - --
CORRECT ANSWER--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. - --CORRECT ANSWER--20
The safety valve is set to automatically reduce pressure at ________ psi. - --
CORRECT ANSWER--150
Your truck has a dual air system and one system loses its pressure. What will
happen? - --CORRECT ANSWER--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: - --CORRECT ANSWER--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? - --CORRECT ANSWER--45
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
, During normal driving, spring brakes are usually held back by: - --CORRECT
ANSWER--Air pressure
The air compressor stops pumping air at what psi? - --CORRECT ANSWER--125
The driver must be able to see a warning before pressure in the service air tanks
falls below ________ psi. - --CORRECT ANSWER--55
Excessive use of the service brakes results in overheating which can lead to: - --
CORRECT ANSWER--Expansion of the brake drums.
The most common type of foundation brake found on heavy vehicles is the: - --
CORRECT ANSWER--S-cam drum
If you must make an emergency stop, brake so you: - --CORRECT ANSWER--
Can steer and your vehicle stays in a straight line.
The braking power of the spring brakes: - --CORRECT ANSWER--Depends on
the service brakes being in adjustment.
The air brake lag distance at 55 mph on dry pavement adds about _______ feet. - -
-CORRECT ANSWER--32
Total stopping distance for air brakes is longer than that for hydraulic brakes due
to _______ distance. - --CORRECT ANSWER--Brake lag
It is accepted that too much heat caused by using your brakes too often can also
cause: - --CORRECT ANSWER--Brake fade or failure
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 3
and Answers
After every working day - --CORRECT ANSWER--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? - --CORRECT ANSWER--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. - --
CORRECT ANSWER--2
To make an emergency stop with air brakes, using the stab braking method, you
should: - --CORRECT ANSWER--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: - --CORRECT ANSWER--
You have to apply the brake pedal harder to control speed on a downgrade.
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 1
,If the air compressor should develop a leak, what keeps the air in the tanks? - --
CORRECT ANSWER--The one way check valve.
To check the brake slack on S-cam brakes you should park on: - --CORRECT
ANSWER--Park on level ground, chock the wheels, and release the parking brakes.
The application pressure gauge shows how much pressure you have: - --
CORRECT ANSWER--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. - --CORRECT ANSWER--20
The safety valve is set to automatically reduce pressure at ________ psi. - --
CORRECT ANSWER--150
Your truck has a dual air system and one system loses its pressure. What will
happen? - --CORRECT ANSWER--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: - --CORRECT ANSWER--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? - --CORRECT ANSWER--45
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 2
, During normal driving, spring brakes are usually held back by: - --CORRECT
ANSWER--Air pressure
The air compressor stops pumping air at what psi? - --CORRECT ANSWER--125
The driver must be able to see a warning before pressure in the service air tanks
falls below ________ psi. - --CORRECT ANSWER--55
Excessive use of the service brakes results in overheating which can lead to: - --
CORRECT ANSWER--Expansion of the brake drums.
The most common type of foundation brake found on heavy vehicles is the: - --
CORRECT ANSWER--S-cam drum
If you must make an emergency stop, brake so you: - --CORRECT ANSWER--
Can steer and your vehicle stays in a straight line.
The braking power of the spring brakes: - --CORRECT ANSWER--Depends on
the service brakes being in adjustment.
The air brake lag distance at 55 mph on dry pavement adds about _______ feet. - -
-CORRECT ANSWER--32
Total stopping distance for air brakes is longer than that for hydraulic brakes due
to _______ distance. - --CORRECT ANSWER--Brake lag
It is accepted that too much heat caused by using your brakes too often can also
cause: - --CORRECT ANSWER--Brake fade or failure
....COPYRIGHT ©️ 2025 ALL RIGHTS RESERVED...TRUSTED & VERIFIED 3
