Question 1: What is the primary purpose of a front brake limiting valve?

• Improves the stopping ability of the vehicle
• Cuts the air pressure to the front brakes by half
• Detects road conditions and switches from slippery to normal as necessary
• Increases the stopping ability of the rear brakes

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?

• Road conditions
• Proper adjustment
• Modulating control valve position (if equipped)
• All of the above (Correct answer)

Correct answer: All of the above

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?

• Two sets of brake controls and two separate air brake systems
• One set of brake controls and two separate air brake systems (Correct answer)
• Two sets of brake controls and one air brake system
• One set of brake controls and one air brake system

Correct answer: One set of brake controls and two separate air brake systems

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?

• In emergency situations
• On front axles only
• On all wheels (Correct answer)
• When parking

Correct answer: On all wheels

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?

• Slack adjusters on S-cam brakes
• Air hoses connected to the brake chambers
• Brake discs or drums
• All of the above (Correct answer)

Correct answer: All of the above

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.

Question 6: During inspection, if a slack adjuster moves less than about one inch where the push rod attaches to it, which of the following statements is true?

• It will fail roadside inspections
• It probably needs adjustment
• It has the appropriate amount of slack (Correct answer)
• The vehicle will be very hard to stop

Correct answer: It has the appropriate amount of slack

It has the appropriate amount of slack. If the slack adjuster moves MORE than about one inch, it probably needs adjustment and will not pass roadside inspections. Too much brake slack will make the vehicle very hard to stop.

Question 7: When testing the air leakage rate (by turning off the engine and releasing the parking brake), what is an acceptable air loss rate?

• Less than 2 psi in one minute for single vehicles and less than 3 psi in one minute for combination vehicles. (Correct answer)
• Less than 3 psi in one minute for both single and combination vehicles
• Less than 3 psi in one minute for single vehicles and less than 2 psi in one minute for combination vehicles.
• Less than 2 psi in one minute for both single and combination vehicles

Correct answer: Less than 2 psi in one minute for single vehicles and less than 3 psi in one minute for combination vehicles.

Less than 2 psi in one minute for single vehicles and less than 3 psi in one minute for combination vehicles. You should test for air leakage with a fully-charged air system. The loss rate should be less than two psi in one minute

Question 8: Which of the following is not a step in testing that the spring brakes come on automatically?

• Release parking brake
• Pump the brake pedal repeatedly
• Shut the engine off
• Pull out the parking brake control knob (Correct answer)

Correct answer: Pull out the parking brake control knob

Pull out the parking brake control knob. To check that spring brakes come on automatically, you should: chock the wheels, release the parking brake, shut the engine off and pump the brakes repeatedly (to reduce air pressure). The

Question 9: If you use controlled braking, which of the following is an acceptable procedure?

• If you need to turn, keep the brakes applied
• Apply the brakes all the way to lock the wheels
• Release the brakes if you need to make a large steering adjustment (Correct answer)
• If your wheels start sliding, press the brake harder

Correct answer: Release the brakes if you need to make a large steering adjustment

Release the brakes if you need to make a large steering adjustment. In controlled braking, you apply the brakes as hard as you can without locking the wheels. If you need to make steering adjustments, you should release the brakes

Question 10: What should you do if the low air pressure warning light comes on?

• Stop and safely park your vehicle as quickly as possible (Correct answer)
• Drive to the nearest service station
• Use stab braking until you are stopped
• No immediate action is required

Correct answer: Stop and safely park your vehicle as quickly as possible

Stop and safely park your vehicle as quickly as possible. If the low air pressure warning comes on there might be a leak in the system. This means that you are in danger of losing your braking ability and you should stop and safel