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200+ Free Virginia CDL Air Brakes Practice Questions

Pass your Virginia CDL Air Brakes Knowledge Test exam on the first try — instant access, no signup required.

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What is the role of the one-way (check) valve at the supply tank?

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Key Facts: Virginia CDL Air Brakes Exam

80%

Minimum CDL knowledge-test passing score

Virginia DMV CDL Knowledge Exams; 49 CFR 383.135

Section 5-1

Virginia CDL manual section for vehicles with air brakes

Virginia DMV CDL Knowledge Exams

$3

Virginia commercial learner’s permit fee

Virginia DMV Apply for a CDL or CLP

14 days

Minimum Virginia CLP holding period before most CDL skills tests

Virginia DMV Commercial Learner’s Permit

20-45 psi

Emergency/parking brake valve pop-out range in Virginia air brake check

Virginia Commercial Driver’s Manual PDF

Use Virginia CDL Manual Section 5-1 as the primary source for the Virginia CDL Air Brakes test. Virginia DMV says CDL knowledge exams are computer-based, require at least 80% correct, and may be taken once per business day. Virginia lists a $3 CLP, a $64 standard 8-year CDL with no endorsements, $1 per endorsement per year, a one-year nonrenewable CLP, and a minimum 14-day CLP holding period before most skills tests. For air brakes, know governor cutoff around 120-140 psi, low-air warning before 55 psi or manufacturer level, emergency brake pop-out at 20-45 psi, and applied leakage limits of 3 psi for single vehicles and 4 psi for combinations in one minute.

Sample Virginia CDL Air Brakes Practice Questions

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

1What 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 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.
2What 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 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.
3At 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 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.
4What 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 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.
5What 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 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.
6At 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 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.
7What 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 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.
8What 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: 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.
9What 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 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.
10What 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 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 Virginia CDL Air Brakes Exam

The Virginia CDL Air Brakes Knowledge Test is required for Virginia CDL or commercial learner permit applicants who need to operate commercial motor vehicles equipped with air brakes without an air-brake restriction. Virginia DMV directs applicants for vehicles with air brakes to study Section 5-1: Air Brakes in the Virginia Commercial Driver’s Manual and states that applicants who do not take the air brakes exam will be restricted to vehicles without air brakes. The exam is part of Virginia’s computer-based CDL knowledge testing program, which requires at least 80% correct and permits only one CDL knowledge-test attempt per business day. Federal FMCSA rules in 49 CFR 383.111(b) require air-brake knowledge across system nomenclature, contaminated air, severed or disconnected lines, low air pressure, pre-trip inspection, en route/post-trip inspection, ABS, emergency stops, and parking-brake operation.

Assessment

Separate computer-based multiple-choice CDL air-brake knowledge test for Virginia applicants who will operate air-brake-equipped CMVs, based on Virginia CDL Manual Section 5-1 and the seven federal air-brake knowledge areas in 49 CFR 383.111(b).

Time Limit

No separate Virginia DMV time limit is published for the Air Brakes knowledge test

Passing Score

At least 80% correct on Virginia CDL knowledge exams and under 49 CFR 383.135

Exam Fee

$3 Virginia CLP; Virginia DMV does not list a separate Air Brakes-only knowledge-test fee (Virginia Department of Motor Vehicles)

Virginia CDL Air Brakes Exam Content Outline

25%

Air Brake System Parts

Compressor, governor, storage tanks, drains, air dryer, alcohol evaporator, safety valve, foot valve, gauges, chambers, slack adjusters, S-cams, ABS, stop light switch, and front brake limiting valve.

15%

Warnings, Dual Systems, and Restrictions

Primary and secondary air circuits, pressure gauges, low-air warning devices, wig-wag operation, spring-brake fail-safe behavior, disconnected air lines, and Virginia/Federal air-brake restrictions.

30%

Inspection and Air Tests

Virginia four-part air brake check, governor cutoff, applied leakage rate, warning-device test, emergency brake test, compressor belt, hoses, drums, linings, pushrod travel, parking brake, and service brake checks.

20%

Using Air Brakes

Normal stops, air conservation, brake lag, stopping distance, brake fade, downgrade control, controlled braking, stab braking, ABS use, low-air emergencies, and parking procedures.

10%

Virginia and FMCSA Rules

Virginia Section 5-1 study requirement, 80% pass standard, once-per-business-day retest rule, CLP fee and holding period, ELDT context, and 49 CFR Part 383 air-brake knowledge standards.

How to Pass the Virginia CDL Air Brakes Exam

What You Need to Know

  • Passing score: At least 80% correct on Virginia CDL knowledge exams and under 49 CFR 383.135
  • Assessment: Separate computer-based multiple-choice CDL air-brake knowledge test for Virginia applicants who will operate air-brake-equipped CMVs, based on Virginia CDL Manual Section 5-1 and the seven federal air-brake knowledge areas in 49 CFR 383.111(b).
  • Time limit: No separate Virginia DMV time limit is published for the Air Brakes knowledge test
  • Exam fee: $3 Virginia CLP; Virginia DMV does not list a separate Air Brakes-only knowledge-test 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

Virginia CDL Air Brakes Study Tips from Top Performers

1Start with Virginia CDL Manual Section 5-1 and make a pressure-number sheet for governor cutoff, warning activation, pop-out, and leak-test limits.
2Practice the Virginia four-part air brake check aloud: gauge/governor cutoff, leakage rate, warning devices, and emergency brake test.
3Separate air-brake context from Combination Vehicles details; know trailer air-line consequences without overstudying fifth-wheel coupling for this exam.
4Use scenario questions for low-air warnings, brake fade, ABS activation, downgrade control, and parking brake misuse.
5Before testing, verify current Virginia DMV fees, CLP requirements, identification documents, and testing rules on official DMV pages.

Frequently Asked Questions

Do I need the Virginia CDL Air Brakes test?

Take it if you need to operate a Virginia commercial motor vehicle equipped with air brakes. Virginia DMV states that applicants who do not take the air brakes exam will be restricted to driving vehicles without air brakes.

What score is required?

Virginia DMV requires at least 80% correct on CDL knowledge exams, and 49 CFR 383.135 requires at least 80% correct on each CDL knowledge test.

What section should I study?

Virginia DMV lists Section 5-1: Air Brakes for vehicles with air brakes. Also review the Virginia Supplement and FMCSA Part 383 standards where they affect air-brake knowledge and restrictions.

What air brake inspection numbers should I know?

Know governor cutoff around 120-140 psi, low-air warning before 55 psi or manufacturer level, emergency/parking brake valve pop-out between 20 and 45 psi, and applied leakage limits of 3 psi in one minute for single vehicles and 4 psi for combinations.

Can I take Virginia CDL knowledge exams repeatedly the same day?

No. Virginia DMV says CDL knowledge exams may be taken only once per business day, and cell phone use during an exam terminates the exam and requires waiting until the next day to retest.