TEXAS CDL AIR BRAKES EXAM PRACTICE EXAM
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2025/2026 Q&A |
INSTANT DOWNLOAD PDF
1. What is the purpose of the air brake system?
• A. To reduce tire wear
• B. To stop and control the vehicle
• C. To improve fuel economy
• D. To inflate suspension systems
Rationale: Air brakes provide the braking force to stop and control heavy vehicles
safely.
2. What is the main cause of brake fade?
• A. Cold weather
• B. Overinflated tires
• C. Excessive heat from overuse of the brakes
• D. Low air pressure in the system
Rationale: Repeated or prolonged braking generates heat, reducing braking
efficiency, known as brake fade.
3. When should you drain air tanks?
• A. Only once per month
• B. Only in cold weather
, • C. At the end of each day’s driving
• D. Only when the low-air warning comes on
Rationale: Draining tanks daily removes water and oil buildup that could damage
the system or freeze in cold weather.
4. What does the low-air pressure warning signal mean?
• A. Air pressure is too high
• B. Air pressure has dropped below a safe level
• C. Brakes are overheating
• D. Emergency brakes are applied
Rationale: The low-air warning alerts the driver that pressure is unsafe and the
brakes could fail if not corrected.
5. What activates the spring brakes?
• A. Air applied to the service brakes
• B. Air pressure applied to the brake pedal
• C. Loss of air pressure
• D. Engine shutdown
Rationale: Spring brakes are designed to automatically apply when air pressure is
lost, serving as a fail-safe.
6. What is the purpose of a safety relief valve?
• A. Protects the system from too much air pressure
• B. Warms the air tanks in cold weather
• C. Holds air pressure during braking
, • D. Cleans out water and oil
Rationale: The safety relief valve opens if pressure exceeds a set limit, preventing
system damage or explosion.
7. How often should you check air brake slack adjusters?
• A. Once a month
• B. During every pre-trip inspection
• C. Every 10,000 miles
• D. Only when brakes feel weak
Rationale: Slack adjusters must be inspected daily to ensure proper brake
adjustment and prevent failures.
8. When testing air leakage in a single vehicle with the brakes released, the loss
rate should be no more than:
• A. 5 psi per minute
• B. 2 psi per minute
• C. 4 psi per minute
• D. 10 psi per minute
Rationale: FMCSA standards allow a maximum loss of 2 psi per minute for single
vehicles with brakes released.
9. Which brakes are used in normal driving?
• A. Parking brakes
• B. Service brakes
• C. Emergency brakes
• D. Spring brakes
, Rationale: Service brakes are applied when the driver presses the brake pedal
during normal operation.
10. What is the “cut-out” level where the air compressor stops pumping air?
• A. 90 psi
• B. 100 psi
• C. 125 psi
• D. 150 psi
Rationale: Most air compressors stop pumping at around 125 psi to prevent over-
pressurization.
11. What is the “cut-in” pressure where the air compressor begins pumping
again?
• A. 150 psi
• B. Around 100 psi
• C. 60 psi
• D. 80 psi
Rationale: The compressor restarts at about 100 psi to maintain a safe pressure
range.
12. What is the purpose of the governor?
• A. Controls fuel injection
• B. Controls when the air compressor pumps air
• C. Regulates brake temperature
• D. Maintains tire pressure
Rationale: The governor tells the air compressor when to cut-in and cut-out.
QUESTIONS AND CORRECT ANSWERS (VERIFIED
ANSWERS) PLUS RATIONALES 2025/2026 Q&A |
INSTANT DOWNLOAD PDF
1. What is the purpose of the air brake system?
• A. To reduce tire wear
• B. To stop and control the vehicle
• C. To improve fuel economy
• D. To inflate suspension systems
Rationale: Air brakes provide the braking force to stop and control heavy vehicles
safely.
2. What is the main cause of brake fade?
• A. Cold weather
• B. Overinflated tires
• C. Excessive heat from overuse of the brakes
• D. Low air pressure in the system
Rationale: Repeated or prolonged braking generates heat, reducing braking
efficiency, known as brake fade.
3. When should you drain air tanks?
• A. Only once per month
• B. Only in cold weather
, • C. At the end of each day’s driving
• D. Only when the low-air warning comes on
Rationale: Draining tanks daily removes water and oil buildup that could damage
the system or freeze in cold weather.
4. What does the low-air pressure warning signal mean?
• A. Air pressure is too high
• B. Air pressure has dropped below a safe level
• C. Brakes are overheating
• D. Emergency brakes are applied
Rationale: The low-air warning alerts the driver that pressure is unsafe and the
brakes could fail if not corrected.
5. What activates the spring brakes?
• A. Air applied to the service brakes
• B. Air pressure applied to the brake pedal
• C. Loss of air pressure
• D. Engine shutdown
Rationale: Spring brakes are designed to automatically apply when air pressure is
lost, serving as a fail-safe.
6. What is the purpose of a safety relief valve?
• A. Protects the system from too much air pressure
• B. Warms the air tanks in cold weather
• C. Holds air pressure during braking
, • D. Cleans out water and oil
Rationale: The safety relief valve opens if pressure exceeds a set limit, preventing
system damage or explosion.
7. How often should you check air brake slack adjusters?
• A. Once a month
• B. During every pre-trip inspection
• C. Every 10,000 miles
• D. Only when brakes feel weak
Rationale: Slack adjusters must be inspected daily to ensure proper brake
adjustment and prevent failures.
8. When testing air leakage in a single vehicle with the brakes released, the loss
rate should be no more than:
• A. 5 psi per minute
• B. 2 psi per minute
• C. 4 psi per minute
• D. 10 psi per minute
Rationale: FMCSA standards allow a maximum loss of 2 psi per minute for single
vehicles with brakes released.
9. Which brakes are used in normal driving?
• A. Parking brakes
• B. Service brakes
• C. Emergency brakes
• D. Spring brakes
, Rationale: Service brakes are applied when the driver presses the brake pedal
during normal operation.
10. What is the “cut-out” level where the air compressor stops pumping air?
• A. 90 psi
• B. 100 psi
• C. 125 psi
• D. 150 psi
Rationale: Most air compressors stop pumping at around 125 psi to prevent over-
pressurization.
11. What is the “cut-in” pressure where the air compressor begins pumping
again?
• A. 150 psi
• B. Around 100 psi
• C. 60 psi
• D. 80 psi
Rationale: The compressor restarts at about 100 psi to maintain a safe pressure
range.
12. What is the purpose of the governor?
• A. Controls fuel injection
• B. Controls when the air compressor pumps air
• C. Regulates brake temperature
• D. Maintains tire pressure
Rationale: The governor tells the air compressor when to cut-in and cut-out.
