CDL AIR BRAKE PRACTICE TEST PRACTICE
SCRIPT UPDATED 2026 TESTED SOLUTIONS
⫸ Why drain water from the compressed air tanks? 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. Answer: 2
⫸ To make an emergency stop with air brakes, using the stab braking
method, you should: 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: Answer: 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? Answer: The one way check valve.
⫸ To check the brake slack on S-cam brakes you should park on:
Answer: Park on level ground, chock the wheels, and release the parking
brakes.
,⫸ The application pressure gauge shows how much pressure you have:
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. Answer: 20
⫸ The safety valve is set to automatically reduce pressure at ________
psi. Answer: 150
⫸ Your truck has a dual air system and one system loses its pressure.
What will happen? 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: 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? Answer: 45
⫸ During normal driving, spring brakes are usually held back by:
Answer: Air pressure
⫸ The air compressor stops pumping air at what psi? Answer: 125
, ⫸ The driver must be able to see a warning before pressure in the
service air tanks falls below ________ psi. Answer: 55
⫸ Excessive use of the service brakes results in overheating which can
lead to: Answer: Expansion of the brake drums.
⫸ The most common type of foundation brake found on heavy vehicles
is the: Answer: S-cam drum
⫸ If you must make an emergency stop, brake so you: Answer: Can
steer and your vehicle stays in a straight line.
⫸ The braking power of the spring brakes: Answer: Depends on the
service brakes being in adjustment.
⫸ The air brake lag distance at 55 mph on dry pavement adds about
_______ feet. Answer: 32
⫸ Total stopping distance for air brakes is longer than that for hydraulic
brakes due to _______ distance. Answer: Brake lag
⫸ It is accepted that too much heat caused by using your brakes too
often can also cause: Answer: Brake fade or failure
SCRIPT UPDATED 2026 TESTED SOLUTIONS
⫸ Why drain water from the compressed air tanks? 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. Answer: 2
⫸ To make an emergency stop with air brakes, using the stab braking
method, you should: 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: Answer: 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? Answer: The one way check valve.
⫸ To check the brake slack on S-cam brakes you should park on:
Answer: Park on level ground, chock the wheels, and release the parking
brakes.
,⫸ The application pressure gauge shows how much pressure you have:
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. Answer: 20
⫸ The safety valve is set to automatically reduce pressure at ________
psi. Answer: 150
⫸ Your truck has a dual air system and one system loses its pressure.
What will happen? 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: 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? Answer: 45
⫸ During normal driving, spring brakes are usually held back by:
Answer: Air pressure
⫸ The air compressor stops pumping air at what psi? Answer: 125
, ⫸ The driver must be able to see a warning before pressure in the
service air tanks falls below ________ psi. Answer: 55
⫸ Excessive use of the service brakes results in overheating which can
lead to: Answer: Expansion of the brake drums.
⫸ The most common type of foundation brake found on heavy vehicles
is the: Answer: S-cam drum
⫸ If you must make an emergency stop, brake so you: Answer: Can
steer and your vehicle stays in a straight line.
⫸ The braking power of the spring brakes: Answer: Depends on the
service brakes being in adjustment.
⫸ The air brake lag distance at 55 mph on dry pavement adds about
_______ feet. Answer: 32
⫸ Total stopping distance for air brakes is longer than that for hydraulic
brakes due to _______ distance. Answer: Brake lag
⫸ It is accepted that too much heat caused by using your brakes too
often can also cause: Answer: Brake fade or failure
