Free Practice Questions for MT CDL Air Brakes
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7 Job WikiKey Facts: MT CDL Air Brakes Exam
80%
Minimum score on each CDL knowledge test
49 CFR 383.135
55 psi
Pressure the low air warning must come on before reaching
Montana CDL Manual Section 5.1.11
20 to 45 psi
Range where tractor and straight truck spring brakes come fully on
Montana CDL Manual Section 5.1.14
32 feet
Approximate brake lag distance added at 55 mph on dry pavement
Montana CDL Manual Section 5.4.4
45 seconds
Maximum time to build from 85 to 100 psi in a dual air system
Montana CDL Manual Section 5.3.3
Montana CDL applicants whose vehicles have air brakes, including air over hydraulic brakes, must pass the Section 5 air brakes knowledge test with at least 80% correct (49 CFR 383.135) or carry the L restriction. Key figures from the June 2026 Montana CDL Manual: governor cut-in about 100 psi and cut-out about 125 psi, safety valve at 150 psi, low air warning before 55 psi, spring brakes fully on at 20 to 45 psi, at least 100 psi in both halves of a dual system before driving, and leakage limits of 2 and 3 psi per minute released or 3 and 4 psi applied (single and combination). On long downgrades, use a low gear and brake down to about 5 mph below your safe speed for about 3 seconds at a time.
Sample MT CDL Air Brakes Practice Questions
Try these sample questions to review concepts for the MT CDL Air Brakes exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 220+ question experience with AI tutoring.
1According to Section 1.1.1 of the Montana CDL Manual, when must an applicant take the air brakes knowledge test?
2An applicant skips the air brake knowledge test. What does the resulting L restriction prohibit?
3A Montana applicant passes the written air brake test, then takes the skills test in a medium-duty truck with air-over-hydraulic brakes. Which restriction will the CDL show?
4Under the federal rule that applies to Montana's CDL knowledge tests, what score is needed to pass the air brake test?
5Montana's CDL Manual defines the air brake (L) restriction. What must a driver pass to show they are qualified for airbrake-equipped vehicles?
6Besides Section 5, which manual section does Section 5 say to study if you will pull a trailer with air brakes?
7Section 5 describes an air brake setup as three braking systems in one. Which list names them?
8What does the emergency brake system in an air brake vehicle use to stop the vehicle when the brake system fails?
9What does the air compressor do?
10If the air compressor has its own oil supply, what does Section 5.1.1 say to do?
About the MT CDL Air Brakes Exam
The Montana CDL Air Brakes Knowledge Test is required for anyone who will drive a commercial motor vehicle with air brakes, including air over hydraulic brakes. Montana MVD gives it at driver license exam stations, and it is based on Section 5 of the Montana CDL Manual. Skipping or failing it leads to the L restriction, and taking the skills test in an air-over-hydraulic vehicle leads to the Z restriction. Independent practice by OpenExamPrep covers system parts and pressures, spring brakes and parking controls, ABS, dual air systems, the Step 5 and Step 7 inspection checks, brake lag, brake fade, and downgrade braking. These four-option questions are an independent study aid, not a copy or simulation of the official MVD test, and they do not replace the skills test.
Exam sponsor: Montana Motor Vehicle Division, Montana Department of Justice. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.
Assessment
A written knowledge test at a Montana MVD driver license exam station, based on Section 5 (Air Brakes) of the Montana CDL Manual and required if your vehicle has air brakes, including air over hydraulic brakes. Skipping or failing it puts an L restriction on the CLP or CDL; the skills tests in an air brake vehicle then include the air brake checks during the pre-trip inspection.
Time Limit
Not published by Montana MVD
Passing Score
At least 80% correct on each knowledge test (49 CFR 383.135)
Exam / Certification Fees
Montana MVD charges $35.54 (intrastate) or $41.72 (interstate) for a CDL or CLP at ages 21-71 and lists no separate air brakes test fee.
Exam sponsor websiteFees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.
Official sources
- Montana MVD Commercial Driver License · Source checked 2026-10-03
- Montana Commercial Driver License Manual (revised June 2026) · Source checked 2026-10-03
- Montana MVD Licensing Fees · Source checked 2026-10-03
- 49 CFR 383.135 - Passing knowledge and skills tests · Source checked 2026-10-03
- 49 CFR 383.95 - Restrictions
Our practice resources: topics covered
We aim to reflect publicly available exam outlines and topic information in our study resources. Coverage, format, and difficulty may differ from the actual exam, and we cannot guarantee that every detail is accurate or current. Confirm exam requirements, fees, and policies with the official exam sponsor.
Air Brake Testing and Restrictions
When the air brakes test is required, the 80% passing score, and the L and Z restrictions, including Montana's definition of what it takes to remove the L restriction.
Air Brake System Parts
Service, parking, and emergency systems; the compressor and governor (cut-in about 100 psi, cut-out about 125 psi); tanks, drains, and alcohol evaporators; the 150 psi safety valve; the brake pedal; s-cam, wedge, and disc brakes; gauges; the low air warning (before 55 psi, or 80-85 psi on many large buses); the stop light switch; and front brake limiting valves.
Spring Brakes and Parking Controls
Spring brakes that come fully on at 20 to 45 psi (typically 20 to 30 psi), the yellow diamond parking knob, modulating and dual parking control valves, and parking with hot or wet brakes.
Antilock Braking Systems
Which air brake vehicles must have ABS, malfunction lamps, how ABS works, braking with ABS on the tractor, the trailer, or both, and what to do if ABS fails.
Dual Air Brake Systems
Primary and secondary systems, building at least 100 psi in both before driving, the warning shut-off above 55 psi, trailer air supply, and losing pressure in one system.
Inspecting Air Brakes
Compressor belt, slack adjusters (about one inch of movement), automatic adjusters, drums and linings, governor checks, released leakage (under 2 psi a minute single, 3 combination), applied leakage (3 psi single, 4 combination), the low air warning test, spring brake pop-out at 20 to 45 psi, build-up from 85 to 100 psi within 45 seconds, and parking and service brake tests.
Using Air Brakes
Normal stops, controlled and stab braking, brake lag (one half second or more; about 32 feet at 55 mph, for a total of over 450 feet), brake fade, braking on long downgrades, low air pressure, and parking brakes.
Preparing for the MT CDL Air Brakes Exam
What You Need to Know
- Passing score: At least 80% correct on each knowledge test (49 CFR 383.135)
- Assessment: A written knowledge test at a Montana MVD driver license exam station, based on Section 5 (Air Brakes) of the Montana CDL Manual and required if your vehicle has air brakes, including air over hydraulic brakes. Skipping or failing it puts an L restriction on the CLP or CDL; the skills tests in an air brake vehicle then include the air brake checks during the pre-trip inspection.
- Time limit: Not published by Montana MVD
- Exam / certification fees: Montana MVD charges $35.54 (intrastate) or $41.72 (interstate) for a CDL or CLP at ages 21-71 and lists no separate air brakes test fee. Official sources
Using Our Practice Resources
- Work through all 220 available questions
- Review every answer and explanation
- Track weak areas and revisit them
- Use our AI tutor for tough concepts
MT CDL Air Brakes: Suggested Study Strategy
Frequently Asked Questions
Who has to take the Montana CDL air brakes test?
Section 1.1.1 of the Montana CDL Manual says you must take the air brakes test if your vehicle has air brakes, including air over hydraulic brakes. If you skip or fail it, your CLP or CDL carries the L restriction, which bars any CMV with air brakes.
What is the difference between the L and Z restrictions?
L bars driving any CMV with air brakes and applies when you skip or fail the air brake knowledge test or take the skills test in a vehicle without air brakes. Z bars only vehicles with full air brakes and applies when you take the skills test in a vehicle with air-over-hydraulic brakes.
What are the governor cut-in and cut-out pressures?
Section 5.1.2 says the governor stops the compressor at the cut-out level, around 125 psi, and lets it start pumping again at the cut-in level, around 100 psi. Check the manufacturer's specifications during the Step 7 check.
When must the low air pressure warning come on?
Section 5.1.11 of the Montana CDL Manual says the warning must come on before tank pressure falls below 55 psi, or one half the governor cut-out pressure on older vehicles. On large buses it commonly signals at 80-85 psi.
At what pressure do the spring brakes come on?
Section 5.1.14 says tractor and straight truck spring brakes come fully on when air pressure drops to 20 to 45 psi, typically 20 to 30 psi. Don't wait for that; stop safely as soon as the low air warning comes on.
What are the maximum air leakage rates?
Section 5.3.3 says that with the engine off and the parking brake released, the loss should be less than 2 psi in one minute for a single vehicle and less than 3 psi for a combination. With the foot brake fully applied for one minute, a loss of more than 3 psi (single) or 4 psi (combination) is too much.
How should I brake on a long downgrade?
Section 5.4.6 says to get into the proper low gear first, because the brakes only supplement engine braking. Apply the brakes just hard enough to feel a definite slowdown, release them at about 5 mph below your safe speed (an application of about 3 seconds), and repeat when you are back at the safe speed.
Are these practice questions the official Montana test?
No. This is independent practice by OpenExamPrep built from the Montana CDL Manual. The four-option questions are a study aid, not a copy or simulation of the official MVD test, and they do not replace the skills tests.