Illinois CDL Practice Exam

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Prepare for the Illinois CDL Exam. Utilize our comprehensive quiz featuring flashcards and multiple choice questions. Enhance your understanding and readiness for the exam with detailed explanations. Ace your CDL test and start your career in commercial driving!

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What is the expected rate of air pressure buildup in dual air brake systems when the engine is at operating rpms?

65 to 75psi within 30 seconds
85 to 100psi within 45 seconds
110 to 120psi within 60 seconds
50 to 90psi within 40 seconds

The correct answer is: 85 to 100psi within 45 seconds

In dual air brake systems, the expected rate of air pressure buildup is crucial for ensuring the brakes function correctly and safely. When the engine is operating at the correct RPMs, the air compressors should quickly build up air pressure for the braking system to be fully operational. The correct answer indicates an expected pressure range of 85 to 100 psi within 45 seconds, which aligns with the typical functioning parameters for most commercial vehicles equipped with dual air brake systems. These systems usually require this level of pressure to ensure the brakes engage effectively, allowing for safe operation of the vehicle. This range is also indicative of the efficiency of the air compressor and its ability to maintain and build pressure quickly, which is essential during vehicle operation to prevent brake failure. A pressure buildup within this time frame ensures that the vehicle's braking system can respond promptly when required. Other ranges for air pressure buildup would not meet the efficiency and safety standards expected in commercial vehicles, impacting overall braking performance and vehicle control.