Free Practice Questions for Tennessee CDL Air Brakes
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Try these sample questions to review concepts for the Tennessee CDL Air Brakes exam. Each question includes a detailed explanation. Start the interactive quiz above for the full 219+ question experience with AI tutoring.
1According to Section 5.1 of the Tennessee CDL Manual, which three distinct systems make up an air brake system on a commercial motor vehicle?
2In the Tennessee CDL Manual's air-brake system description, what does the engine-driven air compressor do?
3Which statement accurately describes how an air compressor may be driven and lubricated on a commercial vehicle?
4What is the primary role of the air compressor governor in an air brake system?
5At approximately what air pressure does the air compressor governor stop pumping air (the cut-out level)?
6When air pressure in the storage tanks drops to approximately what level will the governor allow the compressor to start pumping again (cut-in level)?
7Why is it necessary to drain air storage tanks regularly on vehicles without automatic drain valves?
8How often should manual air tank drains be opened and drained according to the Tennessee CDL Manual?
9During cold weather, why might an air-brake system use an alcohol evaporator?
10What maintenance does an alcohol evaporator require during cold weather operation?
About the Tennessee CDL Air Brakes Exam
Tennessee Driver Services administers a separate CDL Air Brakes knowledge test for applicants who plan to operate commercial vehicles with air brakes. Air brakes are a qualification rather than an endorsement. Failing or omitting the knowledge component, or skills-testing without air brakes, results in Restriction L; testing in an air-over-hydraulic vehicle results in Restriction Z. Tennessee does not publish a definitive CDL knowledge-test language list, while federal rules prohibit interpreters for knowledge tests and require English for skills tests. Independent OpenExamPrep practice is an English-language four-option MCQ study adaptation based on Section 5, not an official translation, test copy, format simulation, or substitute for hands-on skills practice.
Exam sponsor: Tennessee Department of Safety and Homeland Security (TDOSHS) Driver Services. The requirements and fees below concern the certification or admission exam, separate from our free practice resources.
Assessment
A separate knowledge test administered at Full-Service Driver Services Centers with scope supplied by Section 5 of the Tennessee CDL Manual. Air brakes are a vehicle qualification rather than an endorsement. The later CDL skills test has vehicle-inspection, basic-control, and on-road segments; the vehicle inspection includes a three-part applied-leakage, low-air-warning, and automatic-pop-out check whose incorrect performance causes an automatic vehicle-inspection failure.
Time Limit
No fixed limit published; allow 20 to 30 minutes under the Tennessee CDL Manual's planning guidance
Passing Score
At least 80% correct under 49 CFR 383.135
Exam / Certification Fees
$70 Class A CDL / $62 Class B or C CDL total; $14 Class A permit / $13 Class B or C permit; no separate air-brakes knowledge-test fee published
Exam sponsor websiteFees, eligibility, and exam policies can change. Confirm them with the exam sponsor before applying or paying.
Official sources
- Tennessee Driver Services Commercial Driver License · Source checked 2026-10-04
- Tennessee Commercial Driver License Manual · Source checked 2026-10-04
- Tennessee Driver Services CDL Fees · Source checked 2026-10-04
- Tennessee Rules and Regulations (Tenn. Comp. R. & Regs. 1340-01-13-.20 Driver License Restrictions) · Source checked 2026-10-04
- 49 CFR 383.95 (Commercial Driver's License Restrictions) · Source checked 2026-10-04
- 49 CFR 383.135 (Passing Knowledge and Skills Tests) · Source checked 2026-10-04
- FMCSA Guidance for 49 CFR 383.133 (CDL Test Methods and Languages) · Source checked 2026-10-04
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 System Parts
Compressor, governor cut-in/cut-out, air storage tanks, manual and automatic drain valves, alcohol evaporators, safety relief valve, foot valve, foundation brakes (S-cam, wedge, disc), pressure gauges, low-air warning device, stop-light switch, and front-brake limiting valves.
Spring Brakes and Parking Controls
Mechanical spring brake operation, automatic application at 20-45 psi, yellow diamond parking knob, compounding force hazards, modulating valves, dual parking control valves, and parking precautions with hot or wet brake drums.
Antilock Braking Systems
Federal ABS mandate dates, yellow malfunction indicator lamps, electronic control unit operation, steering control during hard stops, and proper braking technique.
Dual Air Brake Systems
Primary and secondary pneumatic circuits, separate tanks and lines sharing one pedal, minimum 100 psi required before operating, and handling single-circuit air pressure loss.
Inspecting Air Brake Systems
Slack adjuster pushrod travel limits, drum and lining inspection, static leakage checks (< 2 psi/min single, < 3 psi/min combination), applied leakage checks (<= 3 psi/min single, <= 4 psi/min combination), low-air warning test, spring brake pop-out test, compressor buildup rate, governor cut-in/cut-out checks, and service/parking brake operational tests.
Using Air Brakes
Normal stopping procedures, brake lag distance (~32 feet at 55 mph, contributing to over 450 feet total stopping distance), emergency stopping (controlled braking vs. stab braking), brake fade mechanics, downgrade snub braking, and low-air emergency stops.
Air Brake Regulations and Restrictions
Tennessee testing rules, 80% passing standard, Restriction L (Code 50: No Air Brakes equipped CMV), Restriction Z (No Full Air Brake equipped CMV), restriction removal procedures, and the mandatory vehicle inspection air brake check.
Preparing for the Tennessee CDL Air Brakes Exam
What You Need to Know
- Passing score: At least 80% correct under 49 CFR 383.135
- Assessment: A separate knowledge test administered at Full-Service Driver Services Centers with scope supplied by Section 5 of the Tennessee CDL Manual. Air brakes are a vehicle qualification rather than an endorsement. The later CDL skills test has vehicle-inspection, basic-control, and on-road segments; the vehicle inspection includes a three-part applied-leakage, low-air-warning, and automatic-pop-out check whose incorrect performance causes an automatic vehicle-inspection failure.
- Time limit: No fixed limit published; allow 20 to 30 minutes under the Tennessee CDL Manual's planning guidance
- Exam / certification fees: $70 Class A CDL / $62 Class B or C CDL total; $14 Class A permit / $13 Class B or C permit; no separate air-brakes knowledge-test fee published Official sources
Using Our Practice Resources
- Work through all 219 available questions
- Review every answer and explanation
- Track weak areas and revisit them
- Use our AI tutor for tough concepts
Tennessee CDL Air Brakes: Suggested Study Strategy
Frequently Asked Questions
Is the air brake test considered an endorsement in Tennessee?
No. In Tennessee and under federal regulations, air brakes are a vehicle qualification rather than an endorsement. Failing the air-brake knowledge test or taking the skills test in a vehicle without air brakes results in Restriction L (Code 50) being placed on the license.
What happens if I take my Tennessee CDL skills test in a vehicle without air brakes?
Your commercial driver license will carry Restriction L (Code 50: Vehicles Without Air Brakes), which prohibits you from operating any commercial motor vehicle equipped with air brakes (Tenn. Comp. R. & Regs. 1340-01-13-.20 and 49 CFR 383.95). If you test in a vehicle with air-over-hydraulic brakes, Restriction Z applies.
What are the maximum acceptable air leakage rates during the pre-trip inspection?
According to Section 5.3 of the Tennessee CDL Manual, static leakage (engine off, brakes released) must be less than 2 psi in one minute for a single vehicle and less than 3 psi for a combination. Under the applied leakage check (holding foot brake firmly), maximum allowable loss is 3 psi in one minute for a single vehicle and 4 psi for a combination.
At what air pressure must the low air pressure warning activate?
Section 5.1.11 requires the low air pressure warning device (optical warning light, buzzer, or wig-wag) to activate before air pressure drops below 55 psi (or one-half the compressor governor cut-out pressure on older vehicles).
At what pressure do the emergency spring brakes automatically pop out?
Section 5.1.14 states that spring brakes automatically pop out and apply mechanically when air pressure drops into the range of 20 to 45 psi (typically between 20 and 30 psi). Drivers must safely pull off the road when the low air warning sounds rather than waiting for spring brakes to apply automatically.
What is the proper snub braking technique on long downgrades?
First shift into an appropriate low gear before beginning the descent. Once vehicle speed reaches the designated safe speed, apply the brakes firmly enough to feel a definite slowdown until speed drops 5 mph below the safe speed (taking about three seconds), release the brakes, and repeat the snubbing cycle when speed climbs back to the safe threshold.
Are these practice questions identical to the official Tennessee air brakes test?
No. These are independent English-language four-option MCQs created by OpenExamPrep from Section 5 of the Tennessee CDL Manual and applicable federal rules. Tennessee does not publish a definitive language list or item format for this knowledge component, so this bank is not an official translation, test copy, format simulation, or substitute for the hands-on skills test.