Illinois CDL Practice Exam

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Study for the Illinois CDL Exam. Utilize comprehensive quizzes featuring multiple choice questions with hints and explanations. Gear up for success on your test!

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Which air brake system utilizes a "power screw" instead of an S-cam to act upon air pressure in a brake chamber and slack adjuster?

Dual Air Brake
Disc Brakes
Modulating Control Valve
Spring Brakes

The correct answer is: Disc Brakes

The correct answer pertains to the disc brake system, which operates differently from traditional air brake systems that rely on S-cams. In disc brakes, the "power screw" mechanism is used to convert air pressure into a clamping force on the brake disc. This method allows for more efficient and direct braking performance compared to the S-cam design, which can lead to quicker response times and more precise control over braking. Disc brakes are increasingly utilized in commercial vehicles due to their ability to offer better stopping power, reduced maintenance, and less fade over longer periods of use. The use of a power screw in these systems helps to enhance the vehicle's braking capabilities, making them a popular choice for modern truck and trailer designs. While other air brake systems like dual air brakes and spring brakes have their own methods of operation—typically reliant on S-cams or other designs—they do not utilize the power screw mechanism. This distinction highlights why the disc brake system is uniquely suited for this characteristic.