Free Kansas DMV CDL — Air Brakes Practice Test 2026
The Kansas CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official Kansas 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 Kansas written test
The Kansas CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official Kansas exam format — always confirm current details with your state DMV.
Practice by topic
Focus on one area at a time — each topic has its own set of Kansas practice questions.
How to pass the first time
- Read the official Kansas 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.
Kansas CDL — Air Brakes test — frequently asked questions
How many questions are on the Kansas CDL — Air Brakes test?
The Kansas 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 Kansas 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 Kansas 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 Kansas 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 Kansas 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 Kansas driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Kansas practice tests
Take the CDL — Air Brakes test in another state
Every Kansas question is written from the official Kansas 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
Kansas CDL — Air Brakes questions with answers
20 sample questions from the Kansas 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. Which chain of events correctly describes how an s-cam brake applies after you press the pedal?
Correct answer: Air enters the brake chamber, the push rod moves the slack adjuster, the camshaft turns the s-cam, and the shoes are forced out against the drum
Air let into the brake chamber pushes the rod out. The rod moves the slack adjuster, which twists the brake camshaft and turns the s-cam. The cam spreads the shoes apart and forces them out against the drum's inner surface.
Source: Kansas Commercial Driver's License Manual — Section 5.1.8, Foundation Brakes
2. Your trailer has ABS but your tractor does not. What does the trailer's ABS make less likely when you brake?
Correct answer: The trailer swinging out
With ABS only on the trailer, trailer swing-out becomes less likely. Steering loss or a jackknife at the tractor can still happen; if one starts, ease off the brakes (when it is safe to do so) until you regain control.
Source: Kansas Commercial Driver's License Manual — Section 5.4.2, Braking with Antilock Brakes
3. Why does the manual warn against setting the parking brakes right after the brakes have gotten very hot, such as at the bottom of a steep grade?
Correct answer: The heat can damage the brakes
Applying the parking brakes to very hot brakes can damage them. Let the brakes cool first and hold the vehicle with wheel chocks on level ground. Freezing in place is the risk with very wet brakes in freezing weather, not with hot ones.
Source: Kansas Commercial Driver's License Manual — Section 5.4.8, Parking Brakes
4. Partway down a long grade, your application pressure gauge shows you need more and more pressure on the brakes just to hold the same speed. What should you do?
Correct answer: Slow down and shift to a lower gear
Needing rising application pressure to keep a steady speed is a sign the brakes are fading. Reduce your speed and drop to a lower gear so the engine does more of the holding back.
Source: Kansas Commercial Driver's License Manual — Section 5.1.10, Application Pressure Gauge
5. Your CDL carries the Z restriction, 'no full air brake equipped CMV.' Which of these may you still drive?
Correct answer: A CMV with air-over-hydraulic brakes
The Z restriction goes to drivers who take the skills test in an air-over-hydraulic vehicle. It bars braking systems that work fully on the air brake principle, but systems that are part air and part hydraulic are still allowed.
Source: Kansas Commercial Driver's License Manual — Section 1, CDL Endorsements & Restrictions
6. The manual describes ABS as an addition to your normal brakes. What does it do to your normal braking capability?
Correct answer: It leaves it unchanged; ABS neither adds to it nor takes away from it
ABS works alongside the regular brakes. It does not raise or lower your normal braking ability; it only comes into play when a wheel is about to lock, which helps you keep control in hard braking.
Source: Kansas Commercial Driver's License Manual — Section 5.1.16, Antilock Braking Systems (ABS)
7. Only your tractor has ABS. During a hard stop, you see in the mirror that the trailer is starting to swing out. What should you do?
Correct answer: Ease off the brakes, as long as you can do that safely
Tractor-only ABS helps you hold steering control and makes a jackknife less likely, but it does nothing for the trailer's wheels. Keep watching the trailer, and if it begins to swing out, let up on the brakes when it is safe to do so.
Source: Kansas Commercial Driver's License Manual — Section 5.4.2, Braking with Antilock Brakes
8. Which of these would NOT cause the spring brakes on an air-braked truck to apply?
Correct answer: Pressing hard on the service brake pedal
Spring brakes apply when the air holding back their springs is removed: you let it out with the parking brake control, a leak empties the system, or pressure sinks to about 20-45 psi. The brake pedal works the service brakes instead, and pressing it while the spring brakes are on can damage the brakes.
Source: Kansas Commercial Driver's License Manual — Section 5.1.14, Spring Brakes
9. On a long downgrade, a couple of your truck's brakes are out of adjustment while the rest are properly adjusted. How does this lead to trouble?
Correct answer: The badly adjusted brakes stop pulling their weight, so the others overheat and fade
Every brake has to carry part of the load. Poorly adjusted brakes stop contributing before the well-adjusted ones, which then take on extra work, overheat, and fade. You can end up without enough braking to control the vehicle.
Source: Kansas Commercial Driver's License Manual — Section 5.4.5, Brake Fading or Failure
10. Which of these situations leads to the L restriction ('no air brake equipped CMV') on a CLP or CDL?
Correct answer: Failing the air brake part of the knowledge test
Skipping or failing the air brake portion of the knowledge test brings the L restriction, which bars you from any CMV with any type of air brakes. A skills test in an air-over-hydraulic vehicle brings the Z restriction instead, an automatic transmission brings E, and certifying intrastate-only driving brings K.
Source: Kansas Commercial Driver's License Manual — Section 1, CDL Endorsements & Restrictions
11. Automatic slack adjusters adjust themselves. When does that self-adjustment take place?
Correct answer: During full brake applications
Automatic slack adjusters take up slack during full brake applications. The manual still says to check them, because a pushrod stroke past the legal limit signals a mechanical problem that self-adjustment is not solving.
Source: Kansas Commercial Driver's License Manual — Section 5.3.2, During Step 5 Walk-around Inspection
12. For an emergency stop in an air-braked vehicle, which two braking methods does the manual describe?
Correct answer: Controlled braking and stab braking
The manual names two emergency methods. Controlled braking means braking firmly but stopping just short of wheel lockup. Stab braking means braking fully, letting off when the wheels lock, and braking fully again once they roll. Both aim to keep the vehicle straight and still able to turn.
Source: Kansas Commercial Driver's License Manual — Section 5.4.3, Emergency Stops
13. A bus is fitted with dual parking control valves. Which of the two do you use to set the spring brakes when you park?
Correct answer: The push-pull valve
You park with the push-pull valve. Its partner is spring-loaded; while you hold it in, it uses air from a separate tank to release the spring brakes so the bus can be moved after main air pressure is lost.
Source: Kansas Commercial Driver's License Manual — Section 5.1.15, Parking Brake Controls
14. A driver estimates his air-braked truck's total stopping distance by adding perception distance, reaction distance, and braking distance. What has he left out?
Correct answer: Brake lag distance
With air brakes, it takes a moment for air to flow through the lines after you press the pedal. The distance covered during that delay, called brake lag distance, is the fourth part of the total along with perception, reaction, and braking distance.
Source: Kansas Commercial Driver's License Manual — Section 5.4.4, Stopping Distance
15. You're applying for a passenger endorsement to drive a bus that has air brakes. Along with the knowledge test on Sections 2 and 4, what other knowledge test must you pass?
Correct answer: The air brakes test (Section 5)
Bus drivers need a passenger endorsement, which calls for passing the Sections 2 and 4 knowledge test. If the bus has air brakes, the manual adds a knowledge test on Section 5, Air Brakes, along with the skills tests for the vehicle class.
Source: Kansas Commercial Driver's License Manual — Section 4, Transporting Passengers Safely
16. The air compressor fills the air storage tanks. What other name does the manual give those tanks?
Correct answer: Reservoirs
The manual also calls the air storage tanks reservoirs. Brake chambers sit at the wheels and push the brake rods, and an evaporator adds alcohol to the air in cold weather; neither one stores the system's air supply.
Source: Kansas Commercial Driver's License Manual — Section 5.1.1, Air Compressor
17. How long can it take locked wheels to begin rolling again after you let off the brakes during stab braking?
Correct answer: Up to about one second
After you let off, it can take as long as a second for locked wheels to roll again. Wait for them to roll before braking fully again, or the vehicle won't straighten out.
Source: Kansas Commercial Driver's License Manual — Section 5.4.3, Emergency Stops
18. During the final air brake check, how does the manual have you confirm that the parking brake will actually hold the vehicle?
Correct answer: With the vehicle stopped and the parking brake on, pull gently against it in a low gear
Stop, apply the parking brake, then put the vehicle in a low gear and pull against the brake gently to see whether it holds. Pressing the service pedal while the spring brakes are on is something the manual tells you to avoid.
Source: Kansas Commercial Driver's License Manual — Section 5.3.3, Step 7 Final Air Brake Check
19. Which of these is NOT part of the manual's braking technique for a long, steep downgrade?
Correct answer: Keep light, steady pressure on the pedal the whole way down
Once in the proper low gear, you brake firmly enough that you feel a definite slowdown, let off about 5 mph below your safe speed (roughly a three-second application), and repeat when you are back up to the safe speed. Constant use of the service brakes is what overheats them and leads to fade.
Source: Kansas Commercial Driver's License Manual — Section 5.4.6, Proper Braking Technique
20. Your truck's low air buzzer works, but the low air warning light is burned out and there's no wig wag. Does the truck meet the low air warning requirement?
Correct answer: No; the rule calls for a visible warning that activates before pressure drops under 55 psi
The required low air warning is a visible one, usually a red light or a wig wag, and it has to activate before tank pressure drops under 55 psi. A buzzer may sound as well, but it is an extra, not a substitute.
Source: Kansas Commercial Driver's License Manual — Section 5.1.11, Low Air Pressure Warning