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Free Practice Questions for Texas CDL Air Brakes

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Key Facts: Texas CDL Air Brakes Exam

80%

Minimum CDL knowledge-test passing score

49 CFR 383.135

7

Required federal air-brake knowledge areas

49 CFR 383.111(b)

$25

Texas DPS original Commercial Learners Permit fee

Texas DPS Driver License Fees

180 days

Texas original CLP validity listed by DPS fee table

Texas DPS Driver License Fees

14 days

Minimum Texas CLP hold before CDL skills testing

Texas DPS CDL FAQ

20-45 psi

Typical manufacturer range for spring brake pop-out/application

Texas CMV Driver Handbook Section 5

85 to 100 psi

Dual-system buildup range commonly checked during air-brake inspection

Texas CMV Driver Handbook Section 5

Use Texas Commercial Motor Vehicle Drivers Handbook Section 5 as the primary source for the Texas CDL Air Brakes test. FMCSA requires the separate air-brake knowledge component to cover seven areas in 49 CFR 383.111(b), and 49 CFR 383.135 requires at least 80% correct. Texas DPS lists a $25 original CLP fee, a $97 standard new CDL fee for ages 18 to 84, a 180-day CLP term, and a 14-day CLP holding period before skills testing. Key study numbers include about 100 psi governor cut-in, about 125 psi cut-out, 150 psi safety valve, low-air warning before the federal/manual threshold, spring brakes around 20-45 psi, 85-to-100 psi buildup within 45 seconds in dual systems, and leak-rate limits of 2/3 psi released and 3/4 psi applied for single/combination vehicles.

Sample Texas CDL Air Brakes Practice Questions

Try these sample questions to review concepts for the Texas CDL Air Brakes exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 220+ question experience with AI tutoring.

1For the Texas CDL Air Brakes test, 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 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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
5For a Texas CDL air-brake vehicle, 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 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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
9Under Texas CMV Driver Handbook Section 5, 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 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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.
10For a Texas CDL air-brake vehicle, 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 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. This Texas item is aligned to Texas Commercial Motor Vehicle Drivers Handbook Section 5 and FMCSA CDL air-brake knowledge standards.

About the Texas CDL Air Brakes Exam

The Texas CDL Air Brakes Knowledge Test is required for Texas CDL or CLP applicants who need to operate commercial motor vehicles equipped with air brakes or air-over-hydraulic brakes without an air-brake restriction. The test is drawn from the Texas Commercial Motor Vehicle Drivers Handbook, especially Section 5, and must satisfy FMCSA CDL knowledge-test standards in 49 CFR Part 383. Study areas include air compressor and governor operation, air tanks and drains, contaminated air, low-air warning devices, dual air systems, spring and parking brakes, ABS, brake lag and stopping distance, emergency braking, brake fade, downgrade braking, foundation brakes, slack adjusters, air-leak and buildup tests, and the legacy front brake limiting valve.

Exam sponsor: Texas Department of Public Safety (DPS) under FMCSA CDL standards. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.

Assessment

Separate multiple-choice CDL air-brake knowledge component based on Texas Commercial Motor Vehicle Drivers Handbook Section 5 and the seven FMCSA air-brake knowledge areas in 49 CFR 383.111(b).

Time Limit

Texas DPS does not publish a separate fixed public time limit for the Air Brakes knowledge test

Passing Score

At least 80% correct under 49 CFR 383.135

Exam / Certification Fees

$25 original CLP; $97 standard new CDL for ages 18 to 84 when issued

Exam sponsor website

Reported exam pass rate: Not published. Texas DPS and FMCSA do not publish an official pass rate for the Texas CDL Air Brakes knowledge test. Exam sponsor website

Fees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.

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.

25%

Air Brake System Parts

Compressor, governor, storage tanks, drains, alcohol evaporator, safety valve, brake pedal, foundation brakes, gauges, stop light switch, ABS, and front brake limiting valve.

15%

Dual Air Systems and Warnings

Primary and secondary systems, pressure gauges, minimum operating pressure, low-air warning devices, wig-wag operation, and low-pressure response.

30%

Inspection and Air Tests

Compressor belt, slack adjuster travel, automatic slack adjuster cautions, drums and linings, hoses, governor checks, leak tests, warning test, spring-brake pop-out, buildup, parking brake, and service brake checks.

20%

Using Air Brakes

Normal stops, controlled and stab braking, ABS use, brake lag, stopping distance, brake fade, downhill braking technique, low-air emergencies, and parking brake exceptions.

10%

Texas and FMCSA Rules

Texas DPS CLP/CDL logistics, CLP validity and holding period, L and Z air-brake restrictions, 49 CFR Part 383 required knowledge, and the 80% passing standard.

Preparing for the Texas CDL Air Brakes Exam

What You Need to Know

  • Passing score: At least 80% correct under 49 CFR 383.135
  • Assessment: Separate multiple-choice CDL air-brake knowledge component based on Texas Commercial Motor Vehicle Drivers Handbook Section 5 and the seven FMCSA air-brake knowledge areas in 49 CFR 383.111(b).
  • Time limit: Texas DPS does not publish a separate fixed public time limit for the Air Brakes knowledge test
  • Exam / certification fees: $25 original CLP; $97 standard new CDL for ages 18 to 84 when issued 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

Texas CDL Air Brakes: Suggested Study Strategy

1Memorize the pressure numbers first: about 100 psi cut-in, about 125 psi cut-out, 150 psi safety valve, low-air warning threshold, spring brakes at about 20-45 psi, and 85-to-100 psi buildup within 45 seconds in dual systems.
2Practice the final air-brake check as a sequence: governor, leak rates, low-pressure warning, spring-brake pop-out, buildup, parking brake, and service brake.
3Separate service, parking, and emergency brake functions; many missed questions confuse foot-valve braking with spring parking brakes.
4Do not skip legacy topics. Texas handbook Section 5 still includes older equipment topics such as front brake limiting valves and wig-wag warnings.
5Review ABS carefully: it helps prevent wheel lockup and maintain control, but it does not necessarily shorten stopping distance or increase normal braking power.
6Use only official Texas DPS, FMCSA, and CFR sources for final review; competitor practice-test wording can conflict with the manual.

Frequently Asked Questions

Who administers the Texas CDL Air Brakes Knowledge Test?

Texas DPS administers Texas CDL knowledge testing under federal CDL standards. The official study source is the Texas Commercial Motor Vehicle Drivers Handbook published by Texas DPS.

What should I study for the Texas CDL Air Brakes test?

Study Texas handbook Section 5. It covers air brake system parts, dual air brake systems, inspection checks, air-leak and buildup tests, low-air warnings, spring brakes, ABS, brake lag, emergency braking, brake fade, downgrade braking, parking brakes, and legacy front brake limiting valves.

What score do I need to pass?

Federal CDL standards in 49 CFR 383.135 require at least 80% correct on each CDL knowledge test, including the air-brake portion.

How much does Texas CDL testing cost?

Texas DPS lists a $25 original CLP fee and a $97 new or renewal CDL fee for ages 18 to 84. DPS publishes CDL/CLP transaction fees rather than a separate Air Brakes-only first-attempt fee.

What happens if I do not pass or do not take the air-brake knowledge component?

Under 49 CFR Part 383, a CLP or CDL issued after failing the air-brake portion, or after skills testing in a vehicle without full air brakes, must carry the applicable air-brake restriction.

Is air brakes an endorsement?

Air brakes are commonly discussed like a separate CDL knowledge test, but federally the issue is an air-brake restriction rather than an endorsement. Passing the knowledge component and demonstrating air-brake inspection/operation as required helps avoid or remove that restriction.