Montana CDL Air Brake Test (MT) 2026

5 out of 5 (39 votes)
80% Passing score
20 Questions
4 Mistakes allowed
Howdy folks! If you're gearing up to get your commercial driver's license with an air brakes endorsement here in Big Sky Country, you're in the right place. Our Montana air brakes CDL test is just what you need to ensure you're fully prepared. This Montana CDL air brakes practice test is packed with 20 carefully selected multiple-choice questions that cover every nook and cranny of air brake systems. Whether it's compressors, reservoirs, brake chambers, or the operational principles and safety protocols that keep everything running smoothly, you'll find it all right here. One unique aspect of air brakes is the brake lag time, and our DMV air brake test has questions specifically addressing this critical concept. Understanding brake lag time is essential for calculating stopping distances accurately, which is a crucial skill for safe driving. To pass this Montana driver's license practice test, you'll need to answer at least 16 questions correctly, ensuring you're well-prepared for the real thing. We know that studying can be tough, so we've included a variety of study aids to help you along the way. If you find yourself stuck on a tricky question, you can request a hint to guide you towards the right answer. And if you get a question wrong, don't worry - you'll get a detailed explanation to help you understand the correct answer. This Montana permit test practice is designed to make your studying as efficient and effective as possible. Our Montana CDL air brakes practice test is regularly updated to reflect the latest driving laws and regulations, so you can be confident that you're studying the most current information available. This ensures that you're always on top of any changes and fully prepared for your CDL air brake test in 2026. While our Montana driving test practice is a great tool, it's important to remember that it doesn't replace a state-certified driver's education or Entry-Level Driver Training (ELDT) course. Instead, think of it as a valuable complement to your studies, helping you to better understand and retain the material covered in your courses. So, buckle up and get ready to ace your CDL air brake test with our comprehensive and up-to-date Montana CDL air brakes practice test. You're one step closer to mastering the fundamentals required for safe and effective air brake operation.
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Sample Montana Air Brakes Test Questions

Question 1

An air-brake-equipped truck or bus must have a low air-pressure warning signal.

  1. A True
  2. B False

Correct answer: A – True

Air-braked trucks and buses are required to have a low-pressure warning signal. Federal equipment standards require a continuous warning when service-reservoir pressure is below 60 psi. During the CDL air-brake inspection procedure, the warning must activate before the tank gauge drops below 55 psi.

Source: Montana Commercial Driver License Manual 2026 — § 5.1.11, “Low Air Pressure Warning”, 49 CFR § 571.121, S5.1.5 – Standard No. 121; Air Brake Systems

Question 2

Which device protects a service air reservoir from losing pressure through a leak between the reservoir and its air source?

  1. A A one-way check valve
  2. B An emergency relay valve
  3. C A tractor protection valve
  4. D The compressor governor

Correct answer: A – A one-way check valve

A one-way check valve, or an equivalent device, protects the service reservoir from pressure loss caused by a failure or leak between the reservoir and its air source. The valve permits air to enter the reservoir but blocks reverse flow through the failed section. The governor controls compressor operation rather than isolating reservoir air.

Source: 49 CFR § 571.121, S5.1.2.3, S5.2.1.4 – Standard No. 121; Air Brake Systems

Question 3

Manually controlled front-brake limiting valves are most likely to be found on which vehicles?

  1. A Some vehicles manufactured before 1975
  2. B All vehicles pulling doubles or triples
  3. C Only recently imported vehicles
  4. D All school buses

Correct answer: A – Some vehicles manufactured before 1975

Some vehicles manufactured before 1975 have a front-brake limiting valve controlled from the cab. The valve’s “slippery” setting reduces pressure to the front brakes, but it also reduces stopping power. The control should normally remain in the “normal” position to provide normal braking performance.

Source: Montana Commercial Driver License Manual 2026 — § 5.1.13, “Front Brake Limiting Valve”

Question 4

If an air-brake safety relief valve repeatedly releases air, what does that indicate?

  1. A The system is operating normally
  2. B System pressure is probably too low
  3. C The compressor is producing too little air
  4. D The air system needs immediate mechanical attention

Correct answer: D – The air system needs immediate mechanical attention

The safety relief valve protects the tank and air system from excessive pressure and is usually set to open at approximately 150 psi. If it releases air, an air-system fault is present. The problem should be repaired by a qualified mechanic rather than treated as normal operation.

Source: Montana Commercial Driver License Manual 2026 — § 5.1.6, “Safety Valve”

Question 5

With the engine at operating rpm, a dual air system with minimum-size tanks should build pressure from 85 to 100 psi within 45 seconds.

  1. A True
  2. B False

Correct answer: A – True

The Montana CDL manual specifies that a dual system with minimum-size tanks should build from 85 to 100 psi within 45 seconds at operating rpm. Vehicles with larger tanks may have a longer acceptable buildup time. The manufacturer’s specifications must be checked when tank size or system design affects the required time.

Source: Montana Commercial Driver License Manual 2026 — § 5.3, “Inspecting Air Brake Systems—Check Rate of Air Pressure Buildup”

Question 6

What is the primary reason for draining air-brake storage tanks?

  1. A To complete the steering inspection
  2. B To activate the compressor governor
  3. C To remove accumulated water and compressor oil
  4. D To test the low-pressure warning signal

Correct answer: C – To remove accumulated water and compressor oil

Compressed air commonly contains moisture and a small amount of compressor oil, which collect in the storage tanks. These contaminants can damage the system, and water may freeze in cold weather and contribute to brake failure. Tanks with manual drains must be drained completely at the end of each driving day.

Source: Montana Commercial Driver License Manual 2026 — § 5.1.4, “Air Tank Drains”

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