Free Texas DMV CDL — Air Brakes Practice Test 2026
The Texas CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official Texas driver handbook — every one has a clear explanation, and you can retake as often as you like with no sign-up.
Content reviewed against official driver handbooks · August 12, 2026
What's on the Texas written test
The Texas CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official Texas exam format — always confirm current details with your state DMV.
Prefer to study on paper?
We make and sell this edition ourselves — it is our own product, not a partner's, and nobody paid us to show it to you. Everything inside it is also free to read on this site; what you are buying is the printable format.
Study offline
Texas Practice Test Pack — 2026 Printable Edition
All 417 Texas practice questions with worked explanations and answer keys — car, motorcycle, CDL and air brakes, in English and Spanish. Eight print-ready PDFs, 605 pages; the car and CDL editions add 146 cut-out road-sign flashcards.
Get the printable edition — $4.99- One-time purchase
- Instant download
- 14-day refund
Practice by topic
Focus on one area at a time — each topic has its own set of Texas practice questions.
How to pass the first time
- Read the official Texas driver handbook at least once before test day.
- Practice by topic to find your weak spots, then fix them.
- Take full-length practice tests until you pass comfortably every time.
- Read every explanation — understanding beats memorizing.
Texas CDL — Air Brakes test — frequently asked questions
How many questions are on the Texas CDL — Air Brakes test?
The Texas CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Our practice tests mirror that format.
How many questions can I miss on the Texas CDL — Air Brakes test?
You can miss up to ~5 of the ~25 questions and still pass — you need ~20 correct, which is 80%.
Can I retake the practice test?
Yes — practice as often as you like, completely free. The questions and answer choices are shuffled each time.
Can I take the Texas practice test in Spanish?
Yes. Every question here is available in English and Spanish — switch languages anytime. Many states also offer the real knowledge test in languages other than English; confirm what Texas offers with your DMV.
Can I practice on my phone?
Yes. The practice tests work in any mobile or desktop browser — no app or sign-up needed — so you can study anywhere.
Are these the real DMV test questions?
No. Our questions are original, written from the current official Texas driver handbook to match the real test's topics and style. We are not affiliated with any DMV or government agency.
What's the best way to study?
Read the Texas driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Texas practice tests
Take the CDL — Air Brakes test in another state
Every Texas question is written from the official Texas driver handbook and checked against its current edition. DMV Test Free is a free, independent study resource — not affiliated with any DMV or government agency. About DMV Test Free
Texas CDL — Air Brakes questions with answers
20 sample questions from the Texas CDL — Air Brakes question bank — each with the correct answer, a short explanation, and the section of the official handbook it comes from.
Show all 20 questions with answers
1. If a leak drains all the air out of the brake system while you drive, what physically applies the spring brakes?
Correct answer: The force of powerful springs no longer held back by air pressure
Powerful springs, normally held back by air pressure, apply the brakes when air pressure is lost. That is why they are called spring brakes — the spring does the work, not the air.
2. Which part of an air brake system pumps the compressed air that the brakes depend on?
Correct answer: The air compressor
The air compressor, driven by the engine through gears or a belt, pumps air into the storage tanks. Every other part of the system relies on the pressure it builds.
3. Which list correctly names all the parts of total stopping distance for a vehicle with air brakes?
Correct answer: Perception + reaction + brake lag + effective braking distance
Total stopping distance with air brakes equals perception distance plus reaction distance plus brake lag distance plus effective braking distance. The brake lag component is what hydraulic-braked vehicles do not have.
4. A driver takes the CDL skills test in a vehicle with an air-over-hydraulic brake system. Which restriction goes on the license?
Correct answer: A Z restriction (no full air brake equipped vehicle)
Testing in a vehicle with air-over-hydraulic brakes results in a Z restriction, which prohibits driving vehicles equipped with full air brakes. The L restriction is broader, barring any air brake system.
5. By law, when must the low air pressure warning signal in an air-braked vehicle activate?
Correct answer: Before tank pressure drops below 55 psi
A low air pressure warning signal is required on vehicles with air brakes and must come on before pressure in the air tanks falls below 55 psi. Some vehicles trigger the warning at a higher level.
6. At roughly what air pressure range will tractor and straight truck spring brakes come fully on by themselves?
Correct answer: 20 to 45 psi
Spring brakes usually apply automatically when air pressure falls into the 20 to 45 psi range. You should already have stopped safely long before pressure drops that far.
7. You are performing the static leakage test on a single vehicle: engine off, fully charged system, foot off the brake, parking brake released, and you time the pressure drop. What is the most the pressure may fall?
Correct answer: 2 psi in one minute
With the brakes released, air loss should be less than 2 psi in one minute for a single vehicle and less than 3 psi in one minute for a combination vehicle.
8. What is "controlled braking" in an emergency stop?
Correct answer: Braking as hard as possible without locking the wheels
Controlled braking means applying the brakes as hard as you can without locking the wheels, keeping steering movements very small while you do it. Locked wheels mean lost steering control.
9. You want a Texas CDL with no air brake restriction. Which pair of requirements must you meet?
Correct answer: Pass the air brakes knowledge test and test in an air-braked vehicle
You must pass the air brakes knowledge test and take the skills test in a vehicle equipped with air brakes, including correctly performing the air brake system checks during the vehicle inspection.
10. When is it acceptable to leave a parked vehicle without the parking brake set, using wheel chocks instead?
Correct answer: When the brakes are very hot or wet in freezing weather
Do not use the parking brakes if the brakes are very hot (after a steep downgrade) or very wet in freezing temperatures, since they could be damaged or freeze to the drums. In those situations, park where you can safely use wheel chocks.
11. Why should you avoid pressing the brake pedal down while the spring brakes are applied?
Correct answer: The combined spring and air forces could damage the brakes
The combined force of the springs and the air pressure could exceed what the brake parts were designed for and damage them. Many systems prevent this, but you should not rely on that protection.
12. During inspection you check push rod travel on an s-cam brake with a manual slack adjuster. When you pull hard on the push rod, about how much movement means the brake needs adjustment?
Correct answer: More than one inch
With the parking brakes released, pull hard on each slack adjuster you can reach. If a push rod moves more than about one inch where it attaches to the slack adjuster, the brake needs adjustment.
13. For a normal stop in a vehicle with air brakes and a manual transmission, how should you use the brake pedal?
Correct answer: Brake smoothly to a safe stop, clutching only near idle rpm
Push the pedal down until the vehicle slows with a safe, smooth stop, and do not push the clutch in until the engine rpm is close to idle. If you have a manual transmission, be in a gear that lets you start moving again once stopped.
14. You park an air-braked truck and leave the cab to make a delivery. What does safe practice require you to do first?
Correct answer: Apply the parking brakes by pulling the yellow diamond-shaped knob out
Any time you park, use the parking brakes — pull the yellow, diamond-shaped knob out to apply them. The exceptions are brakes that are very hot or very wet in freezing temperatures.
15. Using the proper snub braking technique on a long downgrade, the safe speed is 40 mph. When and how should you brake?
Correct answer: At 40 mph, brake firmly down to about 35 mph, release, and repeat
Once the vehicle reaches the safe speed, apply the brakes hard enough to feel a definite slowdown and reduce speed about 5 mph below it (to about 35 mph), then release. Repeat each time the vehicle drifts back up to the safe speed.
16. Why should you drain the air storage tanks on a vehicle with manually operated drain valves at the end of each day of driving?
Correct answer: To remove water and oil that could freeze and cause brake failure
Compressed air carries water and a little compressor oil into the tanks. If not drained daily, the water can freeze in cold weather and cause brake failure.
17. At 55 mph, roughly how much extra stopping distance does brake lag alone add for an air-braked vehicle?
Correct answer: About 32 feet
At 55 mph, the 0.4-second brake lag adds about 32 feet of travel before the brakes even begin to work. That distance is on top of perception, reaction, and effective braking distance.
18. A roadside inspector finds a vehicle's brakes out of adjustment and its air system leaking beyond the allowed rate. What can happen to that vehicle?
Correct answer: It can be placed out of service until the brakes are repaired
Brakes out of adjustment or excessive air loss are safety defects that can put a vehicle out of service until repaired. Driving with defective brakes is both illegal and dangerous.
19. One half of your dual air brake system suddenly loses pressure on the highway. What should you do?
Correct answer: Stop right away and have the air brake system fixed
Either the low pressure warning or braking that feels different tells you one system has failed. The other system can still stop the vehicle, but you should stop right away and have the brakes repaired.
20. What job does an alcohol evaporator perform in some air brake systems?
Correct answer: It reduces the chance of ice forming in air brake valves in cold weather
The alcohol evaporator introduces alcohol into the air system to help keep ice from forming in valves and other parts during cold weather. Its container should be checked and filled daily in cold weather.