Free Montana DMV CDL — Air Brakes Practice Test 2026
The Montana CDL — Air Brakes knowledge test has ~25 questions, and you need ~20 correct (80%) to pass. Practice free with questions written from the official Montana 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 Montana written test
The Montana CDL — Air Brakes knowledge test has ~25 questions; you need ~20 correct (80%) to pass.
Based on the official Montana 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 Montana practice questions.
How to pass the first time
- Read the official Montana 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.
Montana CDL — Air Brakes test — frequently asked questions
How many questions are on the Montana CDL — Air Brakes test?
The Montana 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 Montana 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 Montana 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 Montana 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 Montana 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 Montana driver handbook, practice by topic to target weak areas, and finish with full-length tests until you consistently pass.
Other Montana practice tests
Take the CDL — Air Brakes test in another state
Every Montana question is written from the official Montana 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
Montana CDL — Air Brakes questions with answers
20 sample questions from the Montana 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. During a trip you find that the safety relief valve on the first air tank has been releasing air. How does the manual treat that?
Correct answer: As a sign that something is wrong and a mechanic should fix it
The safety valve keeps pressure in the first tank and everything downstream from climbing too high. Its usual opening point is 150 psi, well above the typical governor cut-out of around 125 psi. The manual says that if this valve lets air out there is a fault, and a mechanic should correct it.
Source: Montana Commercial Driver License Manual — Section 5.1.6, Safety Valve
2. An applicant takes the CDL skills test in a truck with air over hydraulic brakes. Under the manual's restriction list, what must the state place on the license?
Correct answer: A Z restriction: no CMV whose braking system works fully on air
The Z restriction applies when the skills test vehicle has air over hydraulic brakes, meaning a system that works partly on air and partly on hydraulics. The driver may not operate a CMV with full air brakes. The L restriction is the broader one, covering any type of air brakes.
Source: Montana Commercial Driver License Manual — CDL Endorsements & Restrictions
3. On an icy road, the driver of a pre-1975 truck moves the front brake limiting valve control to "slippery." What does the manual say about that choice?
Correct answer: It cuts stopping power; braking is unlikely to skid the front wheels even on ice, so the control belongs in "normal"
The "slippery" setting halves the usual air pressure to the front brakes. The manual says that lowers the vehicle's stopping power, that front wheel braking is good in all conditions, and that testing found braking rarely makes the front wheels skid, ice included.
Source: Montana Commercial Driver License Manual — Section 5.1.13, Front Brake Limiting Valve
4. You have just come down a steep grade and your brakes are very hot. The manual says not to use the parking brakes yet. How does it say to hold the vehicle in the meantime?
Correct answer: With wheel chocks, on a level surface
Heat can damage very hot brakes if the parking brakes are applied, so the manual says to let them cool first. Until then, park on a level surface and use wheel chocks.
Source: Montana Commercial Driver License Manual — Section 5.4.8, Parking Brakes
5. On a long grade your application pressure gauge shows you are using more and more pressure just to keep your speed steady. What does the manual tell you to do?
Correct answer: Slow down and shift to a lower gear
Needing more application pressure to hold a steady speed is a sign of brake fade. The manual's response is to reduce speed and drop to a lower gear.
Source: Montana Commercial Driver License Manual — Section 5.1.10, Application Pressure Gauge
6. You are checking that the low pressure warning works on a truck with a dual air system. Which tank's pressure does the manual's 55 psi standard apply to?
Correct answer: The tank with the lowest air pressure
The warning has to come on before pressure falls under 55 psi, and for dual systems the manual specifies the tank holding the least pressure. The test is done with the engine off and the electrical power on, pumping the brake pedal to bring the pressure down.
Source: Montana Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
7. A driver wants a passenger endorsement and will drive a bus that has air brakes. Besides the test on Sections 2 and 4, what does the manual say this driver must also pass?
Correct answer: A knowledge test on Section 5, Air Brakes
The passenger section says bus drivers earn the endorsement by passing a written test covering Sections 2 and 4, and that those whose bus has air brakes must pass one on Section 5 as well.
Source: Montana Commercial Driver License Manual — Section 4, Transporting Passengers Safely
8. You are unsure whether your truck was built late enough to be required to have ABS. Where does the manual say to look for the date of manufacture?
Correct answer: On the vehicle's certification label
ABS is required on air-braked truck tractors built from March 1, 1997, and on other air-braked vehicles built from March 1, 1998. The manual points you to the certification label to find when the vehicle was made.
Source: Montana Commercial Driver License Manual — Section 5.1.16, Antilock Braking Systems (ABS)
9. According to the manual, how well the spring brakes hold or stop a vehicle comes down to what?
Correct answer: Whether the brakes are properly adjusted
The manual ties the power of the spring brakes to brake adjustment. With poorly adjusted brakes, the regular brakes and the emergency and parking brakes will both fall short.
Source: Montana Commercial Driver License Manual — Section 5.1.14, Spring Brakes
10. On a long downgrade in the proper low gear, you brake until you are about 5 mph under your "safe" speed and then release. About how long does the manual say that brake application should last?
Correct answer: About three seconds
The manual's downgrade technique is to brake firmly enough that you can feel the vehicle clearly slowing, release at roughly 5 mph below the safe speed, and repeat once speed climbs back to the safe speed. Each application should take about three seconds.
Source: Montana Commercial Driver License Manual — Section 5.4.6, Proper Braking Technique
11. A bus has lost its main air pressure and the spring brakes are on. The driver uses the spring-loaded control fed by a separate air tank to release them and move. Why does the manual say to plan that move carefully?
Correct answer: The separate tank holds only enough air to release the brakes a few times
On vehicles with dual parking control valves, pushing the spring-loaded control in sends air from a separate tank to release the spring brakes, and letting go brings them back on. The manual warns that this supply is good for only a few releases, so a poorly planned move could leave you stopped somewhere dangerous.
Source: Montana Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
12. On Montana's CDL vehicle inspection test, what happens if you do not correctly explain and demonstrate every one of the four parts of the air brake check?
Correct answer: You automatically fail the vehicle inspection test
The manual's vehicle inspection section says the air brake check has four parts: the air gauge and governor cutout check, the leakage rate test, the warning device test and the emergency brake test. Getting any of them wrong is an automatic failure of the vehicle inspection test.
Source: Montana Commercial Driver License Manual — Section 11.1.2, Air Brake or Hydraulic Brake Check
13. Step 7 of the seven-step inspection in Section 2 includes a hydraulic brake check. What does the Air Brakes section tell drivers of air-braked vehicles to do at that step?
Correct answer: Do the final air brake checks in place of the hydraulic brake check
The Air Brakes section says its Step 7 checks replace the hydraulic brake check described in Section 2. They cover the governor, air leakage, the low pressure warning, the spring brakes, pressure buildup, the parking brake and the service brakes.
Source: Montana Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
14. Your vehicle applies its spring brakes with a modulating control valve on the dash. How does the manual say to park it?
Correct answer: Push the lever to the end of its travel and lock it there with the locking device
A modulating valve lets you bring the spring brakes on gradually; the farther the lever moves, the harder they apply. For parking, the manual says to take the lever all the way and secure it with its locking device.
Source: Montana Commercial Driver License Manual — Section 5.1.15, Parking Brake Controls
15. With air brakes there is a short delay between pressing the pedal and the brakes working. About how long does the manual say the air takes to travel through the lines?
Correct answer: One half second or more
The manual calls this delay brake lag. Hydraulic brakes work at once, but in an air system the air needs half a second or more to reach the brakes.
Source: Montana Commercial Driver License Manual — Section 5.4.4, Stopping Distance
16. Suppose the low pressure warning signal has failed and air is leaking away unnoticed. What does the manual say this could lead to in a single-circuit air system?
Correct answer: Sudden emergency braking
Without a working warning you could lose air and not know it. The manual says that in a single-circuit system the result can be sudden emergency braking, while in a dual system stopping distance grows and only limited braking is possible before the spring brakes apply.
Source: Montana Commercial Driver License Manual — Section 5.3.3, Step 7 Final Air Brake Check
17. Your vehicle has air over hydraulic brakes, not full air brakes. According to the manual's list of knowledge tests, do you need to take the air brakes test?
Correct answer: Yes; the air brakes test is required for vehicles with air brakes, air over hydraulic included
Section 1 says the air brakes test is required for anyone whose vehicle is air-braked, and it expressly counts air over hydraulic brakes.
Source: Montana Commercial Driver License Manual — Section 1.1.1, Knowledge Tests
18. The manual gives two other names for the brake pedal on an air-braked vehicle. Which pair is it?
Correct answer: Foot valve or treadle valve
The manual says the brake pedal is also known as the foot valve or the treadle valve. Trolley valve and Johnson bar are names the manual uses for the trailer hand valve, which is a different control.
Source: Montana Commercial Driver License Manual — Section 5.1.7, The Brake Pedal
19. You are about to park in freezing weather and your brakes are very wet. What does the manual suggest doing before you stop?
Correct answer: Drive in a low gear with light brake pressure so the brakes warm up and dry out
Very wet brakes can freeze in cold weather and leave the vehicle unable to move if the parking brakes are set. The manual's remedy is to brake lightly in a low gear until the brakes have warmed and dried, and it says to hold the vehicle with wheel chocks on level ground when the parking brakes should not be used.
Source: Montana Commercial Driver License Manual — Section 5.4.8, Parking Brakes
20. The manual describes air brakes as three braking systems in one. What does it say the emergency brake system is built from?
Correct answer: Parts of the service brake system and the parking brake system
The Air Brakes section says the emergency brake system draws on components of both the service brakes and the parking brakes so the vehicle can still be stopped after a brake system failure. It is not described as a separate hydraulic backup.
Source: Montana Commercial Driver License Manual — Section 5, Air Brakes