CDL Air Brakes endorsement Exam With
Actual Questions & Verified Answers, Plus
Explained Rationales/Expert Verified For
Guaranteed Pass 2026/Latest
Updated/Instant Download Pdf
1. What is the primary purpose of air brakes on a commercial
vehicle?
A. To increase engine power
B. To provide stopping power for heavy vehicles
C. To reduce fuel consumption
D. To improve steering control
B. To provide stopping power for heavy vehicles
Air brakes are designed to safely stop large, heavy commercial
vehicles, which require more force than hydraulic brakes.
2. How does a dual air brake system work?
A. It uses one air tank for both front and rear brakes
B. It has two separate air systems, each operating different sets of
brakes
C. It combines hydraulic and air brakes
D. It only operates in emergency situations
B. It has two separate air systems, each operating different sets of
brakes
Dual air brake systems have separate circuits to ensure that if one
fails, the other can still stop the vehicle.
, 3. What is the normal air pressure range in a fully charged system?
A. 50–70 psi
B. 90–100 psi
C. 110–130 psi
D. 70–80 psi
B. 90–100 psi
Most air brake systems operate between 90 and 100 psi for optimal
braking performance.
4. What should you do if the low air pressure warning comes on
while driving?
A. Ignore it
B. Stop and safely park the vehicle as soon as possible
C. Pump the brakes to increase pressure
D. Reduce speed and continue driving
B. Stop and safely park the vehicle as soon as possible
A low air pressure warning indicates that the brakes may fail soon, so
it is critical to stop immediately.
5. How often should air tanks be drained?
A. Once a week
B. Once a month
C. Daily or after each trip
D. Only when the brake pedal feels soft
C. Daily or after each trip
Moisture and oil accumulate in air tanks, so draining daily prevents
brake failure.
6. What is “brake lag”?
A. Delay between pressing the pedal and the brakes applying
B. Brakes overheating after long use
, C. Brakes locking during sharp turns
D. The time it takes to release air from the system
A. Delay between pressing the pedal and the brakes applying
Brake lag is the time needed for compressed air to reach the brakes
after the pedal is pressed.
7. What is the purpose of the air compressor?
A. To pump fuel into the engine
B. To generate air pressure for the brake system
C. To release excess air from the system
D. To operate the steering system
B. To generate air pressure for the brake system
The air compressor supplies compressed air necessary to operate the
brakes.
8. What does the spring brake do when air pressure is released?
A. Keeps the vehicle in motion
B. Applies the parking/emergency brakes
C. Releases the service brakes
D. Engages the engine brake
B. Applies the parking/emergency brakes
Spring brakes are held back by air pressure and automatically engage
when pressure drops.
9. What is a safety check you should perform on air brakes before
driving?
A. Test engine temperature
B. Check air pressure build-up and warning signals
C. Inspect seat belts
D. Measure tire tread only
Actual Questions & Verified Answers, Plus
Explained Rationales/Expert Verified For
Guaranteed Pass 2026/Latest
Updated/Instant Download Pdf
1. What is the primary purpose of air brakes on a commercial
vehicle?
A. To increase engine power
B. To provide stopping power for heavy vehicles
C. To reduce fuel consumption
D. To improve steering control
B. To provide stopping power for heavy vehicles
Air brakes are designed to safely stop large, heavy commercial
vehicles, which require more force than hydraulic brakes.
2. How does a dual air brake system work?
A. It uses one air tank for both front and rear brakes
B. It has two separate air systems, each operating different sets of
brakes
C. It combines hydraulic and air brakes
D. It only operates in emergency situations
B. It has two separate air systems, each operating different sets of
brakes
Dual air brake systems have separate circuits to ensure that if one
fails, the other can still stop the vehicle.
, 3. What is the normal air pressure range in a fully charged system?
A. 50–70 psi
B. 90–100 psi
C. 110–130 psi
D. 70–80 psi
B. 90–100 psi
Most air brake systems operate between 90 and 100 psi for optimal
braking performance.
4. What should you do if the low air pressure warning comes on
while driving?
A. Ignore it
B. Stop and safely park the vehicle as soon as possible
C. Pump the brakes to increase pressure
D. Reduce speed and continue driving
B. Stop and safely park the vehicle as soon as possible
A low air pressure warning indicates that the brakes may fail soon, so
it is critical to stop immediately.
5. How often should air tanks be drained?
A. Once a week
B. Once a month
C. Daily or after each trip
D. Only when the brake pedal feels soft
C. Daily or after each trip
Moisture and oil accumulate in air tanks, so draining daily prevents
brake failure.
6. What is “brake lag”?
A. Delay between pressing the pedal and the brakes applying
B. Brakes overheating after long use
, C. Brakes locking during sharp turns
D. The time it takes to release air from the system
A. Delay between pressing the pedal and the brakes applying
Brake lag is the time needed for compressed air to reach the brakes
after the pedal is pressed.
7. What is the purpose of the air compressor?
A. To pump fuel into the engine
B. To generate air pressure for the brake system
C. To release excess air from the system
D. To operate the steering system
B. To generate air pressure for the brake system
The air compressor supplies compressed air necessary to operate the
brakes.
8. What does the spring brake do when air pressure is released?
A. Keeps the vehicle in motion
B. Applies the parking/emergency brakes
C. Releases the service brakes
D. Engages the engine brake
B. Applies the parking/emergency brakes
Spring brakes are held back by air pressure and automatically engage
when pressure drops.
9. What is a safety check you should perform on air brakes before
driving?
A. Test engine temperature
B. Check air pressure build-up and warning signals
C. Inspect seat belts
D. Measure tire tread only
