North Carolina CDL Air Brakes Practice Test (NC) 2

5 out of 5 (66 votes)
80% Passing score
20 Questions
4 Mistakes allowed
If you're getting ready to secure your commercial driver's license in NC, our NC CDL air brakes practice test is an essential resource. This DMV air brake test includes 20 multiple-choice questions that thoroughly cover crucial topics such as air brake components, operation, safety inspections, and calculating stopping distances. For example, understanding the dual air brake systems is vital, as it enhances safety by providing a backup if one system fails. To pass, you need to answer at least 16 questions correctly, mirroring the real requirements of the North Carolina air brakes CDL test. One of the standout features of our NC driving test practice is the immediate feedback provided after each question. This includes detailed explanations to help you understand why a specific answer is correct or incorrect. This feedback is instrumental in reinforcing your knowledge and ensuring you're well-prepared for the real DMV air brake test. Our NC permit practice test sources all its questions directly from the official state drivers manual. This means you're studying the same material that will appear on the actual CDL test, ensuring that your preparation is aligned with the state's standards. This practice permit test provides a no-pressure environment, allowing you to focus on learning and understanding the material without the stress of the actual test. In North Carolina, driving conditions can vary greatly from the coastal plains to the mountainous regions. Our NC CDL air brakes practice test takes into account these local driving conditions, ensuring you're prepared for the diverse environments you'll encounter on the road. Whether navigating through the bustling city streets of Raleigh or the winding roads of the Blue Ridge Mountains, being well-versed in air brake systems is crucial for safety. Prepare confidently for your NC air brakes CDL test with our comprehensive North Carolina CDL air brakes practice test. It's the ideal way to ensure you cover all necessary topics in one thorough session, equipping you with the knowledge and confidence to succeed on test day.
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Sample North Carolina Air Brakes Test Questions

Question 1

Which statement correctly describes the work performed by a commercial vehicle’s brakes?

  1. A. Brake drums release heat almost immediately after heavy braking
  2. B. Brakes develop greater stopping power as they become hotter
  3. C. A heavier vehicle requires the brakes to do more work and absorb more heat during a stop
  4. D. Brake temperature has no effect on braking performance

Correct answer: C. – A heavier vehicle requires the brakes to do more work and absorb more heat during a stop

The North Carolina manual explains that heavier vehicles require their brakes to perform more work and absorb more heat when stopping. Excessive heat can reduce friction, expand brake drums, and cause brake fade. Hot brakes do not become more effective, and continued overheating can eventually prevent the vehicle from slowing or stopping properly.

Source: North Carolina Commercial Driver License Manual — § 2.6.1, “Stopping Distance”; § 5.4.5, “Brake Fading or Failure”

Question 2

While maintaining a steady speed on a downgrade, which change may indicate brake fade?

  1. A. Less application pressure is needed
  2. B. The low-air warning turns off
  3. C. Increasing application pressure is needed
  4. D. The parking-brake control remains released

Correct answer: C. – Increasing application pressure is needed

Needing progressively greater application pressure to maintain the same speed is a warning that the brakes may be fading. The driver should reduce speed and use a lower gear. Increased pressure can also result from brakes being out of adjustment, an air leak, or another mechanical problem, so the braking system must be checked.

Source: North Carolina Commercial Driver License Manual — § 5.1.10, “Application Pressure Gauge”

Question 3

Why must the proper low gear be selected before descending a long or steep grade?

  1. A. The service brakes should supplement the engine’s braking effect
  2. B. The transmission must remain disengaged during the descent
  3. C. The parking brakes should control most of the vehicle’s speed
  4. D. A higher gear prevents the brake drums from expanding

Correct answer: A. – The service brakes should supplement the engine’s braking effect

On a long or steep downgrade, engine braking should be the principal method of controlling speed. The service brakes supplement that braking effect and remain available when additional slowing is necessary. Depending too heavily on the service brakes creates excessive heat, which can cause brake fade and eventually leave insufficient braking power.

Source: North Carolina Commercial Driver License Manual — § 5.4.6, “Proper Braking Technique”

Question 4

During a dual air-system buildup test at operating engine speed, what result should normally be observed?

  1. A. Pressure rises from 85 to 100 psi within three minutes
  2. B. Pressure rises from 85 to 100 psi within 45 seconds
  3. C. The compressor cuts out at 75 psi
  4. D. The safety valve opens at 125 psi

Correct answer: B. – Pressure rises from 85 to 100 psi within 45 seconds

The North Carolina manual states that pressure in a dual air system should normally rise from 85 to 100 psi within 45 seconds when the engine is operating at the proper rpm. A vehicle with larger-than-minimum air tanks may require more time. In that situation, the manufacturer’s buildup specifications should be checked before deciding that the system is defective.

Source: North Carolina Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

Question 5

On an older air-brake vehicle with a manual front-brake limiting valve, the control should remain in the “normal” position for normal stopping power. True or false?

  1. A. True
  2. B. False

Correct answer: A. – True

The normal position provides normal front-wheel braking power. Moving a manual limiting valve to the slippery position reduces air pressure to the front brakes and decreases the vehicle’s stopping power. The manual teaches that front-wheel braking is effective under all conditions and that front-wheel braking skids are unlikely even on ice.

Source: North Carolina Commercial Driver License Manual — § 5.1.13, “Front Brake Limiting Valve”

Question 6

With the engine off, brakes released, and foot brake not applied, a single vehicle should lose less than how many psi in one minute?

  1. A. 1 psi
  2. B. 2 psi
  3. C. 3 psi
  4. D. 4 psi

Correct answer: B. – 2 psi

The North Carolina manual sets the released-brake leakage rate at less than 2 psi in one minute for a single vehicle, such as a straight truck or bus. The system should be fully charged, the engine turned off, and the parking brake released for this check. Excessive leakage must be corrected before the vehicle is driven.

Source: North Carolina Commercial Driver License Manual — § 5.3.3, “Step 7 Final Air Brake Check”

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