North Carolina Air Brakes Knowledge Test CDL Practice Test
Practice with real NC Air Brakes exam questions and detailed explanations. Rated 4.8 stars by 1,000+ drivers.
Written by CDL holders and exam prep experts · Updated April 2026
Free Questions
10
Passing Score
80%
Time Limit
No time limit specified
Prerequisites
General Knowledge test must be completed first
What is the Air Brakes Knowledge Test Test?
The Air Brakes knowledge test is required for commercial vehicles equipped with air brake systems. Passing this test demonstrates your knowledge of air brake operation, inspection procedures, and safety protocols, and removes the 'L' restriction from your CDL.
Knowledge test to remove 'L' restriction (no air brakes) from CDL
Topic Breakdown
Air Brake System Components
~8 questions
- Compressor and reservoir systems
- Brake chambers and slack adjusters
- Air lines and fittings
Inspection and Testing
~7 questions
- Pre-trip inspection procedures
- Air pressure tests
- Brake adjustment checks
Safe Driving Practices
~6 questions
- Proper braking techniques
- Following distance requirements
- Downhill braking procedures
Emergency Procedures
~4 questions
- Air pressure loss procedures
- Emergency braking systems
- Brake failure protocols
Free Practice Questions
10 questionsQuestion 1 of 10
Which braking technique may be used to stop quickly when you do not have ABS?
Browse North Carolina Air Brakes Questions
- 1. Which braking technique may be used to stop quickly when you do not have ABS?
- 2. Parking or emergency brakes of trucks and buses can be legally held on by ____ pressure.
- 3. Stab braking:
- 4. Why drain water from compressed air tanks?
- 5. The spring brakes of a tractor-trailer will activate once air pressure drops to approximately:
- 6. Some air brake systems have an alcohol evaporator. What may happen if you don't keep the proper level of alcohol?
- 7. Which procedure is used for the spring brake test?
- 8. A slack adjuster free play needs to be adjusted if it is more than about ____ when you pull hard on it.
- 9. Repeatedly partially increasing and pressing the brake pedal may result in:
- 10. Characteristics of dual air brake systems include:
Study Tips for North Carolina
- 1Memorize the 3-part air brake system: service brakes, parking brakes, emergency brakes
- 2Know cut-in pressure (100 psi) and cut-out pressure (125 psi) - exact numbers tested
- 3Learn the air brake lag time: 0.5 seconds for brakes to engage after pressing pedal
- 4Master the air brake inspection: check air loss rate (less than 4 psi in 1 minute)
- 5Remember: never downshift while braking - this is a common wrong answer choice
North Carolina CDL Information
Age Requirements
Intrastate: 18+ · Interstate: 21+
CDL Renewal
Every 5 years
ELDT Required
Yes — ELDT (Entry-Level Driver Training) from FMCSA-registered provider
North Carolina Division of Motor Vehicles (NCDMV)
Official CDL Portal →Career Opportunities
Frequently Asked Questions
If you plan to drive a commercial vehicle equipped with air brakes, you must pass the air brakes knowledge test to remove the 'L' restriction from your CDL.
Air Brakes Study Resources
Other North Carolina CDL Tests
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