CDL Airbrakes Practice Test 2

Question 1

What is the primary purpose of a front brake limiting valve?

Accepted Answer

Answer

A front brake limiting valve, found primarily on older commercial vehicles, has the primary purpose of reducing the air pressure to the front brakes by half when set to the 'slippery' position. This was intended to prevent the front wheels from locking up on slick surfaces. Modern air brake systems are designed to provide effective front braking under all conditions without such a valve.

Question 2

Which of the following will affect the stopping power of spring brakes?

Accepted Answer

All of the above

Answer

The stopping power of spring brakes is influenced by several factors. Road conditions (like ice or wet pavement) directly impact traction, while proper adjustment of the brakes ensures they engage effectively. Additionally, if equipped, the modulating control valve allows the driver to control the application of spring brakes, affecting their stopping force. All these elements collectively determine the spring brakes' effectiveness.

Question 3

A dual air brake system has which of the following features?

Accepted Answer

One set of brake controls and two separate air brake systems

Answer

A dual air brake system is a safety feature that divides the air brake system into two independent circuits, typically one for the front axle and one for the rear axle. While the driver uses a single brake pedal (one set of controls), each circuit has its own air tanks, lines, and components. This design ensures that if one system fails, the other can still provide some braking capability, enhancing safety.

Question 4

Where are foundation brakes used?

Accepted Answer

On all wheels

Answer

On all wheels.  Foundation brakes (usually s-cam drum brakes) are used at each wheel to provide equal stopping power.  Commercial vehicles have emergency and parking brakes in addition to foundation brakes.

Question 5

Which of the following parts of the air brake systems should be checked during the pre-trip walk around inspection?

Accepted Answer

All of the above

Answer

All of the above.  During step 5 of the pre-trip inspection, you should check the slack adjuster, air hoses and brake drums/discs of the air brake systems.

CDL Practice Test

CDL Practice Test

CDL Airbrakes Practice Test 2