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200+ Free NJ CDL Air Brakes Test Practice Questions

Pass your New Jersey Commercial Driver License (CDL) Air Brakes Knowledge Test exam on the first try — instant access, no signup required.

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On the New Jersey CDL Air Brakes knowledge test, what is the shape and color of the trailer air supply control on a tractor?

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2026 Statistics

Key Facts: NJ CDL Air Brakes Test Exam

80%

Minimum passing score for CDL knowledge tests

NJ MVC CDL Tests and 49 CFR 383.135

$125

New Jersey Commercial Examination Test Receipt fee

NJ MVC CDL Tests

7 days

Required wait after a failed CDL knowledge test

NJ MVC CDL Tests and CDL FAQ

180 days

Test Receipt period before renewal is needed if not passed

NJ MVC CDL FAQ

360 days

Validity of CDL test scores

NJ MVC CDL Tests

14 days

CLP practice period before skills test unless waived

NJ MVC CDL Tests

Study Section 5 of the New Jersey Commercial Driver License Manual. Know governor cut-in around 100 psi and cut-out around 125 psi, daily tank draining, low-air warning before 60 psi, spring-brake application around 20-45 psi, buildup and leak-test limits, ABS behavior, brake lag, downgrade braking, parking controls, foundation brake inspection, alcohol evaporators, and the legacy front-brake limiting valve. NJ MVC lists a $125 non-refundable Test Receipt fee, 80% passing score, seven-day knowledge-test retake wait, 180-day Test Receipt period, 360-day score validity, and 14-day CLP practice period before the skills test unless waived.

Sample NJ CDL Air Brakes Test Practice Questions

Try these sample questions to test your NJ CDL Air Brakes Test exam readiness. Each question includes a detailed explanation. Start the interactive quiz above for the full 200+ question experience with AI tutoring.

1For New Jersey CDL air-brake testing, what component compresses air for the air brake system?
A.The air dryer
B.The air compressor
C.The brake chamber
D.The slack adjuster
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The air compressor pumps air into the air storage tanks. It is driven by the engine, either through belts or directly. The air dryer removes moisture from the compressed air, the brake chamber converts air pressure into mechanical force at each wheel, and the slack adjuster transfers that force to the S-cam.
2Under the NJ MVC Commercial Driver License Manual air-brakes section, what is the typical air compressor governor cut-out pressure range?
A.60 to 80 psi
B.100 to 125 psi
C.125 to 140 psi
D.150 to 175 psi
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The governor cuts out the compressor (stops pumping) at about 125 to 140 psi. It cuts back in (resumes pumping) at about 100 to 125 psi. This pressure range keeps the system safely above the low-pressure warning threshold of 60 psi while preventing over-pressurization.
3On the New Jersey CDL Air Brakes knowledge test, at what pressure does the air compressor governor typically cut IN to resume pumping?
A.60 to 80 psi
B.100 to 125 psi
C.125 to 140 psi
D.145 to 150 psi
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The governor typically cuts in at 100 to 125 psi, signaling the compressor to resume pumping. It cuts out at 125 to 140 psi when system pressure is sufficient. Together these limits maintain a safe operating range well above the 60 psi low-pressure warning.
4During New Jersey CDL air-brake preparation, what is the purpose of the air dryer in the brake system?
A.To cool the air before storage
B.To remove moisture and oil before air reaches the tanks
C.To increase compressed air pressure
D.To warn the driver of low pressure
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The air dryer uses a desiccant cartridge to remove water vapor and oil from compressed air before it enters the storage tanks. Removing moisture prevents corrosion, contamination of brake components, and dangerous freezing of air lines in cold weather.
5For an NJ commercial vehicle equipped with air brakes, what is the function of the wet tank (supply or service reservoir)?
A.It cools brake fluid
B.It is the first storage tank where moisture collects before air moves to the other tanks
C.It supplies air only to the trailer
D.It activates the parking brakes
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The wet tank is the first storage reservoir downstream of the compressor. Most moisture and oil that gets past the air dryer settles there before clean air moves on to the primary and secondary tanks. Drivers must drain the wet tank daily to prevent contamination of the rest of the system.
6For New Jersey CDL air-brake testing, at what pressure does the safety valve in the supply tank typically open to release excess air?
A.100 psi
B.125 psi
C.150 psi
D.200 psi
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The safety valve, installed in the supply (wet) tank, is set to open at about 150 psi. It is a backup that protects the system if the governor fails to cut out the compressor. If the valve releases, the compressor or governor needs immediate repair.
7Under the NJ MVC Commercial Driver License Manual air-brakes section, what is the role of the foot valve (also called the treadle or service brake valve)?
A.It locks the parking brake
B.It supplies air to the brake chambers in proportion to how hard the driver presses the pedal
C.It drains water from the tanks
D.It controls the trailer air supply
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The foot valve (treadle valve) meters air to the brake chambers in proportion to how far the driver depresses the brake pedal. Pressing harder sends more air, applying more braking force. Releasing the pedal exhausts air from the chambers, allowing the springs and slack adjusters to release the brakes.
8On the New Jersey CDL Air Brakes knowledge test, what does the brake chamber do?
A.Stores compressed air for emergencies
B.Converts air pressure into mechanical force through a pushrod
C.Cools brake drums during use
D.Acts as a backup for the parking brake
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. A brake chamber is a sealed housing with a diaphragm or piston. When air pressure enters, the diaphragm pushes a pushrod outward. The pushrod rotates the slack adjuster and S-cam, which forces the brake shoes against the drum to apply braking force.
9During New Jersey CDL air-brake preparation, what is the role of the slack adjuster on an S-cam brake?
A.It cushions the impact of hard braking
B.It transfers force from the pushrod to the S-cam and can be adjusted to compensate for lining wear
C.It bleeds water from the system
D.It limits maximum air pressure
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The slack adjuster is a lever that connects the brake chamber pushrod to the S-cam. As the pushrod extends, the slack adjuster rotates the S-cam, which pushes the brake shoes against the drum. It can be adjusted to maintain proper pushrod travel as brake linings wear.
10For an NJ commercial vehicle equipped with air brakes, what does the S-cam do in an S-cam drum brake?
A.It releases air from the lines
B.It rotates between the brake shoes, forcing them outward against the drum
C.It cools the brake drum
D.It activates the low-pressure warning
Explanation: The New Jersey MVC Commercial Driver License Manual Section 5 covers this air-brake point. The S-cam is an S-shaped piece of steel between the two brake shoes. When the slack adjuster rotates it, the wide part of the S forces the shoes outward against the drum, creating friction and slowing the wheel. When air pressure is released, return springs pull the shoes back and rotate the S-cam to its original position.

About the NJ CDL Air Brakes Test Exam

The New Jersey CDL Air Brakes Knowledge Test covers the air-brake material in Section 5 of the New Jersey Commercial Driver License Manual for drivers who operate trucks, buses, or other commercial motor vehicles equipped with air brakes. The tested material includes air compressor and governor operation, storage tanks and draining, low-air warnings, pressure buildup and leak tests, spring and parking brakes, dual air systems, ABS, brake lag, emergency braking, slack adjusters, foundation brakes, inspection procedures, alcohol evaporators, and older front brake limiting valves. MVC administers CDL knowledge testing through New Jersey Driver Testing Centers under FMCSA CDL standards.

Assessment

Multiple-choice New Jersey MVC CDL written knowledge testing covering air-brake systems and Section 5 air-brake knowledge. NJ MVC publishes a 50-question General Knowledge test plus additional separate knowledge tests, but does not publish a separate public Air Brakes item count. Federal rules require an air-brake restriction when an applicant fails the air-brake portion, and restriction removal depends on passing the applicable air-brake knowledge and skills-test conditions.

Time Limit

Computer-based MVC knowledge testing; no separate public Air Brakes time limit found in official NJ MVC sources

Passing Score

80% minimum on CDL knowledge tests

Exam Fee

$125 non-refundable Commercial Examination Test Receipt fee (New Jersey Motor Vehicle Commission (MVC))

NJ CDL Air Brakes Test Exam Content Outline

NJ CDL Manual Section 5.1

Air Brake System Parts

Compressor, governor, storage tanks, drains, alcohol evaporator, safety valve, brake pedal, foundation brakes, slack adjusters, gauges, low-air warning, spring brakes, parking controls, ABS, and older front brake limiting valves.

NJ CDL Manual Section 5.2

Dual Air Brake Systems

Primary and secondary systems, separate tanks and gauges, minimum pressure before driving, warning behavior, and driver response when either system loses pressure.

NJ CDL Manual Section 5.3

Inspecting Air Brakes

Compressor belt, slack adjusters, drums, linings, hoses, low-air warning, spring-brake pop-out, governor cut-in/cut-out, buildup rate, air leakage, parking brake, and service brake checks.

NJ CDL Manual Section 5.4

Using Air Brakes

Normal stops, ABS, controlled braking, stab braking, brake lag, stopping distance, brake fade, downgrade technique, low-air response, parking, hot brakes, wet brakes, and tank draining.

How to Pass the NJ CDL Air Brakes Test Exam

What You Need to Know

  • Passing score: 80% minimum on CDL knowledge tests
  • Assessment: Multiple-choice New Jersey MVC CDL written knowledge testing covering air-brake systems and Section 5 air-brake knowledge. NJ MVC publishes a 50-question General Knowledge test plus additional separate knowledge tests, but does not publish a separate public Air Brakes item count. Federal rules require an air-brake restriction when an applicant fails the air-brake portion, and restriction removal depends on passing the applicable air-brake knowledge and skills-test conditions.
  • Time limit: Computer-based MVC knowledge testing; no separate public Air Brakes time limit found in official NJ MVC sources
  • Exam fee: $125 non-refundable Commercial Examination Test Receipt fee

Keys to Passing

  • Complete 500+ practice questions
  • Score 80%+ consistently before scheduling
  • Focus on highest-weighted sections
  • Use our AI tutor for tough concepts

NJ CDL Air Brakes Test Study Tips from Top Performers

1Memorize the pressure numbers in Section 5: 150 psi safety valve, 125 psi governor cut-out, 100 psi cut-in, 85 to 100 psi buildup in 45 seconds for dual systems, 60 psi low-air warning, and 20 to 45 psi spring-brake range.
2Practice the final air-brake check as a sequence: warning signal, spring-brake pop-out, governor cut-in/cut-out, buildup rate, leakage rate, parking brake, and service brake.
3Separate service, parking, and emergency brake functions in your notes so you do not confuse foot-valve operation with spring-brake operation.
4Review ABS behavior carefully: ABS helps keep control during hard braking but does not replace normal brakes or guarantee a shorter stop.
5Do not skip the legacy items in the NJ manual, including alcohol evaporators and older front brake limiting valves.

Frequently Asked Questions

Who administers the New Jersey CDL Air Brakes test?

New Jersey MVC administers CDL knowledge testing at Driver Testing Centers and publishes the New Jersey Commercial Driver License Manual used for preparation.

What score do I need to pass?

NJ MVC states that CDL knowledge tests require at least 80% correct, and 49 CFR 383.135 also requires at least 80% correct on CDL knowledge tests.

Is air brakes an endorsement in New Jersey?

NJ MVC lists that there is no separate endorsement for Air Brakes, but air-brake knowledge and vehicle testing matter because air-brake restrictions can limit which CMVs a driver may operate.

What happens if I fail the air-brake portion?

Federal CDL rules require an air-brake restriction on a CLP or CDL if the applicant fails the air-brake knowledge portion and is still issued a credential.

How often can I retake a failed CDL knowledge test in New Jersey?

NJ MVC says failed CDL knowledge-test applicants must wait seven days before retesting. The Test Receipt is valid for 180 days, and test scores are valid for 360 days.

What New Jersey manual section should I study?

Study Section 5, Air Brakes, of the New Jersey Commercial Driver License Manual. If you will pull a trailer with air brakes, MVC also directs applicants to study Section 6, Combination Vehicles.