A truck's foundation brakes are known to be out of adjustment. Someone argues that its strong parking springs make that defect irrelevant to parking and emergency braking. What is the flaw?
Correct answer: Spring-brake effectiveness also depends on proper brake adjustment
Spring force still acts through the wheel-brake mechanism. The manual warns that poor adjustment can impair both regular braking and spring-operated emergency or parking braking.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.1.14 - Spring Brakes; printed5-3, physical79. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A driver familiar with a newer yellow push-pull parking knob is assigned an older air-braked truck with a labeled parking lever. What should guide the driver's use of it?
Correct answer: The assigned truck's identified control and operating instructions
The manual describes newer push-pull knobs and different controls on older vehicles. Drivers need to identify and learn the assigned vehicle's parking control, rather than transferring a shape-based assumption.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.1.15 - Parking Brake Controls; corroborating 5.4.8 on physical85/printed5-9; printed5-3, physical79. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A straight truck has a dual air-brake system but only one service-brake pedal. A trainee thinks a second pedal must be missing. Which explanation resolves the concern?
Correct answer: Separate air circuits can share a single set of brake controls
A dual air system has separate air systems with their own tanks, hoses and lines, while using one set of brake controls. The manual describes typical axle assignments, not one universal layout.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.2 - Dual Air Brake (text, not the single-circuit Figure5.4); printed5-5, physical81. Current NCDMV-linked copy reviewed September 13, 2026. ↗
Before departure in a dual-air straight truck, one reservoir reading is normal but the other remains below the vehicle's required operating pressure. What should the driver do?
Correct answer: Wait for both circuits to meet the operating requirements
The manual directs the driver to watch both system readings and allow both to build adequate pressure before driving. A normal reading for one circuit does not verify the other; unexplained failure to build requires correction.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.2 - Dual Air Brake; printed5-5, physical81. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A pre-trip check identifies excessive brake pushrod travel on a truck equipped with automatic slack adjusters. An unqualified driver proposes turning the adjuster until the reading looks acceptable. What is the better response?
Correct answer: Arrange qualified diagnosis and correction of the underlying fault
An automatic adjuster found out of adjustment may have a fault, an installation problem or related foundation-brake trouble. Manual resetting can mask the cause. Brake service must respect applicable qualifications and the manufacturer's procedures.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.2 - During Step 5 Walk-around Inspection > automatic slack adjusters; corroborating 49CFR396.25 and DTNA S2 article in audit; printed5-6, physical82. Current NCDMV-linked copy reviewed September 13, 2026. ↗
During the walk-around, a hose connected to a brake chamber has been rubbing against a bracket and is visibly worn. No hiss is heard at that moment. How should it be treated?
Correct answer: As a brake-system defect needing attention before operation
The air-brake inspection specifically includes chamber hoses that are cut or worn from rubbing. Absence of an audible leak at that moment does not make visible hose damage acceptable.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.2 - During Step 5 Walk-around Inspection > Brake Drums, Linings, and Hoses; printed5-6, physical82. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A correctly conducted, safely secured pre-trip check confirms that a truck's low-air warning does not operate as specified. The supply gauge itself works. What conclusion follows?
Correct answer: The failed warning needs correction despite the working gauge
The warning is intended to alert the driver before depleted pressure severely limits braking. The gauge and warning have separate roles; the check has found a defect rather than an acceptable substitute arrangement.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.3 - Step 7 Final Air Brake Check > Test Low Pressure Warning Signal; equipment applicability corroborated by 49CFR393.51; printed5-6, physical82. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A dual-air truck has larger-than-minimum reservoirs. Its manufacturer specifies a buildup time appropriate to that configuration. How should a trainee assess its pressure buildup?
Correct answer: Use the applicable manufacturer specification for that equipment
The manual explicitly notes that larger tanks may take longer to fill and directs the reader to manufacturer specifications. Equipment-specific context matters; this item does not set a numerical test or scoring limit.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.3 - Check Rate of Air Pressure Buildup; printed5-7, physical83. Current NCDMV-linked copy reviewed September 13, 2026. ↗
In the manual's safely secured reservoir-leakage check, the engine is shut off before the pressure loss is measured. What is the reason for measuring without the compressor adding air?
Correct answer: It prevents replenishment from hiding the pressure loss
A loss measurement must not be offset by fresh compressed air. The source distinguishes released and applied brake conditions and vehicle configurations; this conceptual item is not a complete test sequence or a leakage-limit question.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.3 - Test Air Leakage Rate; printed5-7, physical83. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A completed check shows that a truck cannot build air pressure fast enough to meet the specification for its actual system. The route is short. What is the appropriate decision?
Correct answer: Do not depart until the buildup problem is corrected
Inadequate buildup can leave too little air for braking during driving. The manual says to have that problem fixed before driving; a short route does not remove the defect.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.3 - Check Rate of Air Pressure Buildup; printed5-7, physical83. Current NCDMV-linked copy reviewed September 13, 2026. ↗
Under the prescribed safe test conditions, a truck remains stationary during a gentle low-gear pull against its applied parking brake. What has that check established?
Correct answer: The parking brake resisted that gentle holding check
The gentle pull is a parking-brake holding check. It does not replace the separate service-brake, air-leakage or warning-device checks, and it is not a full assessment of braking performance.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.3.3 - Test Parking Brake; Test Service Brakes; printed5-7, physical83. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A driver has already recognized a hazard and pressed the pedal, but time is still needed for air to travel through the system and apply the wheel brakes. Which part of stopping is being described?
Correct answer: The air-brake lag after the pedal is pressed
Brake lag is the air-system delay after pedal operation and before the brakes act. It is separate from the driver's perception and reaction intervals and must be included in stopping-distance planning.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.4.4 - Stopping Distance; Figure5.6 on physical85/printed5-9; printed5-8, physical84. Current NCDMV-linked copy reviewed September 13, 2026. ↗
A truck's drum brakes have become excessively hot from overuse, although reservoir pressure remains normal. Why can stopping effectiveness still decline?
Correct answer: Heat can reduce lining friction and expand the drums
Air pressure alone does not establish the condition of the friction brakes. Excessive heat can change the lining's friction and expand a drum, increasing shoe travel and reducing effective contact.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.4.5 - Brake Fading or Failure; printed5-9, physical85. Current NCDMV-linked copy reviewed September 13, 2026. ↗
Some brakes on a truck are out of adjustment and contribute less than their share during repeated braking. What additional problem can develop at the brakes still doing most of the work?
Correct answer: They can overheat and fade from carrying more of the braking load
The manual explains that brakes not doing their share leave the remaining brakes to do more work. Those brakes can overheat and fade, so one part of the system cannot simply compensate indefinitely for another.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.4.5 - Brake Fading or Failure; printed5-9, physical85. Current NCDMV-linked copy reviewed September 13, 2026. ↗
While an air-braked straight truck is moving, its low-air warning comes on and pressure is falling. Service braking is still available. What is the safest objective?
Correct answer: Reach a safe stop and park as soon as possible while control remains
The manual directs the driver to stop and safely park promptly after a low-air warning. Automatic spring-brake application is not a safe stopping plan: remaining service-brake control is limited as the air supply falls.
Source: North Carolina Commercial Driver License Manual, 2005 CDL Testing System, Version July 2014; Section 5 > 5.4.7 - Low Air Pressure; printed5-9, physical85. Current NCDMV-linked copy reviewed September 13, 2026. ↗
