Texas CDL Air Brakes Practice Test

The Texas CDL Air Brakes test is a multiple-choice knowledge test you take for your commercial learner's permit. Texas Department of Public Safety (DPS), Driver License Division says you need 80% to pass (source).

Last updated Oct 7, 2026. FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC.

By Scott Wilder, Editor

Last reviewed against the Texas CDL manual on October 7, 2026

Scott Wilder on X | scottwilderhq.com

FirstTry CDL is a CDL permit test prep site by Hive Asset Group, LLC. It offers free exam-style practice tests built from the official CDL manual. FirstTry CDL is not affiliated with any DMV, FMCSA or government agency. Practice questions are exam-style questions built from the official CDL manual, not actual test questions.

Texas CDL permit facts

What	What Texas says	Source
Air Brakes pass mark	80%	Official page
CLP fee	$25 (expires 180 days from issue)	Official page
CLP validity	180 days, or until your Texas driver license expires, whichever is first	Official page
CLP holding period	Hold the CLP at least 14 days before the skills test	Official page
Knowledge test retest rule	After a failed test, your application stays active for 90 days. After 90 days or three failed attempts, whichever comes first, you must submit a new application, pay fees again and retest	Official page
Test languages	All CDL and CLP knowledge exams are English only since June 1, 2026. Spanish tests are no longer offered and interpreters are not allowed. Skills tests are English only. Drivers who cannot show enough English are not eligible for a Texas CDL or CLP.	Official page

20 question Air Brakes practice test

1. You are slowing down a tractor-trailer that has ABS. What should you do as you slow?
1. A. Watch the tractor and trailer and back off the brakes if safe
2. B. Press the brakes harder every second
3. C. Look only at the road ahead
4. D. Release the brakes fully at once
Show answer
Answer: A. Watch the tractor and trailer and back off the brakes if safe
Monitor the tractor and trailer, and back off the brakes if it is safe.
From the official CDL manual, section 5.4.2.
2. When should you use the parking brakes?
1. A. Only on hills
2. B. Whenever you park
3. C. Only in cold weather
4. D. Only when the tanks are low
Show answer
Answer: B. Whenever you park
The manual says to use the parking brakes whenever you park.
From the official CDL manual, section 5.1.15.
3. In a dual air brake system, which system supplies air to the trailer?
1. A. Only the primary system
2. B. Only the secondary system
3. C. Both systems
4. D. Neither one. The trailer has its own air.
Show answer
Answer: C. Both systems
Both systems supply air to the trailer, if there is one.
From the official CDL manual, section 5.2.
4. You are about to pull on the slack adjusters to check them. How should the vehicle be set up first?
1. A. On level ground, wheels chocked, parking brakes released
2. B. On level ground, wheels chocked, parking brakes applied
3. C. On a slight slope, wheels not chocked, parking brakes released
4. D. Engine running at fast idle, parking brakes applied
Show answer
Answer: A. On level ground, wheels chocked, parking brakes released
You chock the wheels on level ground and release the parking brakes so the adjusters can move.
From the official CDL manual, section 5.3.2.
5. The low pressure warning does not work on a single-circuit air system. What could happen?
1. A. You could lose air without knowing, then get sudden emergency braking
2. B. The compressor would stop building air
3. C. The service brakes would apply more gently
4. D. The governor would cut out at 100 psi
Show answer
Answer: A. You could lose air without knowing, then get sudden emergency braking
Without a warning you would not know pressure is falling, and a single-circuit system could suddenly apply emergency braking.
From the official CDL manual, section 5.3.3.
6. Only your trailer has ABS. You lose steering control and the tractor starts to jackknife. What should you do?
1. A. Brake harder to straighten the trailer
2. B. Turn the wheel sharply and keep braking
3. C. Let up on the brakes if it is safe, until you gain control
4. D. Shift to a higher gear
Show answer
Answer: C. Let up on the brakes if it is safe, until you gain control
Let up on the brakes, if you can do so safely, until you gain control.
From the official CDL manual, section 5.4.2.
7. What does the safety valve protect the air brake system from?
1. A. Too little pressure
2. B. Water in the tanks
3. C. Worn brake linings
4. D. Too much pressure
Show answer
Answer: D. Too much pressure
The safety valve protects the tank and the system from too much pressure.
From the official CDL manual, section 5.1.6.
8. Why is manual adjustment of an automatic slack adjuster dangerous?
1. A. It voids the vehicle's registration
2. B. It always makes the brakes lock up
3. C. It can give a false sense of security about the brakes
4. D. It makes the air tanks leak
Show answer
Answer: C. It can give a false sense of security about the brakes
The manual says it may give the driver a false sense of security.
From the official CDL manual, section 5.3.2.
9. Engine off, parking brake released, system fully charged. What is the air loss limit per minute for a combination vehicle?
1. A. One psi
2. B. Three psi
3. C. Two psi
4. D. Five psi
Show answer
Answer: B. Three psi
With the engine off and the parking brake released, a combination vehicle should lose less than three psi in one minute.
From the official CDL manual, section 5.3.3.
10. An automatic adjuster's pushrod stroke is over the legal limit. What does this usually show?
1. A. The tires are worn
2. B. A mechanical problem or a bad installation
3. C. The tank has too much air
4. D. The brakes are working better
Show answer
Answer: B. A mechanical problem or a bad installation
The manual says it indicates a mechanical problem or an improper installation.
From the official CDL manual, section 5.3.2.
11. Before driving a dual air brake vehicle, the compressor should build at least how much pressure in both systems?
1. A. 100 psi
2. B. 55 psi
3. C. 80 psi
4. D. 125 psi
Show answer
Answer: A. 100 psi
The manual says to build a minimum of 100 psi in both the primary and secondary systems.
From the official CDL manual, section 5.2.
12. Which air brake system applies and releases the brakes when you use the brake pedal in normal driving?
1. A. The service brake system
2. B. The parking brake system
3. C. The emergency brake system
4. D. The foundation brake system
Show answer
Answer: A. The service brake system
The service brakes work when you press and release the brake pedal.
From the official CDL manual, section 5.
13. A bus with air brakes was built in June 1998. Must it have ABS?
1. A. No, only truck tractors must have ABS
2. B. No, ABS was not required until the year 2000
3. C. Only if it also pulls an air brake trailer
4. D. Yes, buses built on or after March 1, 1998 must
Show answer
Answer: D. Yes, buses built on or after March 1, 1998 must
Buses and other air brake vehicles built on or after March 1, 1998 are required to have ABS.
From the official CDL manual, section 5.1.16.
14. Why should you do the service brake test before you drive on the road?
1. A. It warms up the brake drums
2. B. It sets the slack adjusters
3. C. It builds air pressure faster
4. D. It may show problems you would not know about until you needed the brakes
Show answer
Answer: D. It may show problems you would not know about until you needed the brakes
The test may show brake problems you would not find until you needed the brakes on the road.
From the official CDL manual, section 5.3.3.
15. What can happen if you keep overusing the service brakes?
1. A. The brakes grip better
2. B. The drums shrink and grab harder
3. C. Brake fade may grow until the vehicle cannot be slowed or stopped
4. D. Nothing, brakes are made for constant use
Show answer
Answer: C. Brake fade may grow until the vehicle cannot be slowed or stopped
Continued overuse may increase brake fade until the vehicle cannot be stopped.
From the official CDL manual, section 5.4.5.
16. On a long downgrade, you must press harder to hold the same speed. The application gauge keeps rising. What should you do?
1. A. Keep pressing harder to hold speed
2. B. Slow down and use a lower gear
3. C. Pump the pedal quickly
4. D. Shift to a higher gear
Show answer
Answer: B. Slow down and use a lower gear
Rising application pressure at the same speed means brake fade, so slow down and use a lower gear.
From the official CDL manual, section 5.1.10.
17. How should you inspect a vehicle that has air brakes?
1. A. Check the air brakes only at the end of the trip
2. B. Check only the air brake parts and skip the rest
3. C. Use a special air brake method instead of the seven steps
4. D. Use the seven-step method and add the air brake checks
Show answer
Answer: D. Use the seven-step method and add the air brake checks
The manual says to use the basic seven-step procedure, with more things to inspect.
From the official CDL manual, section 5.3.
18. What does the emergency brake system use to stop the vehicle when a brake system fails?
1. A. A separate set of brakes used only in emergencies
2. B. Parts of the service and parking brake systems
3. C. Only the parking brake system
4. D. Only the trailer brakes
Show answer
Answer: B. Parts of the service and parking brake systems
The emergency system shares parts of the service and parking brake systems.
From the official CDL manual, section 5.
19. How does an air brake system turn on the brake lights?
1. A. A cable tied to the brake pedal linkage
2. B. A switch built into the governor
3. C. An electric switch that works by air pressure
4. D. The low air pressure warning switch
Show answer
Answer: C. An electric switch that works by air pressure
The stop light switch is electric but is operated by air pressure.
From the official CDL manual, section 5.1.12.
20. When can brakes get out of adjustment quickly?
1. A. When they are cold
2. B. When they are hot
3. C. When the engine is off
4. D. When they are new
Show answer
Answer: B. When they are hot
The manual says this happens especially when brakes are hot.
From the official CDL manual, section 5.4.5.

Texas CDL Air Brakes questions

What score do you need to pass the Texas CDL Air Brakes test?

Texas says you need 80% to pass the Air Brakes test.

Is the Texas CDL Air Brakes test the same as other states?

The Air Brakes test is built on the same federal knowledge standards in every state, so the topics match the CDL manual. Texas uses its own handbook: https://www.dps.texas.gov/internetforms/Forms/DL-7C.pdf

How much does a CDL permit cost in Texas?

CLP fee: $25 (expires 180 days from issue).

What languages is the Texas CDL knowledge test offered in?

All CDL and CLP knowledge exams are English only since June 1, 2026. Spanish tests are no longer offered and interpreters are not allowed. Skills tests are English only. Drivers who cannot show enough English are not eligible for a Texas CDL or CLP.

Sources

https://www.dps.texas.gov/internetforms/Forms/DL-7C.pdf
https://www.dps.texas.gov/section/driver-license/driver-license-fees
https://www.dps.texas.gov/section/driver-license/how-do-i-apply-commercial-driver-license
Manual sections used in this test: 5; 5.1.10; 5.1.12; 5.1.15; 5.1.16; 5.1.6; 5.2; 5.3; 5.3.2; 5.3.3; 5.4.2; 5.4.5

Air Brakes practice test in nearby states