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CDL Quiz 12

1. In air brake vehicles, the parking brake should be used
Anytime the vehicle is parked.
To hold your speed when going downhill.
As little as possible.

2. To check the slack adjusters on S-cam brakes, you should
Stop on level ground and apply the parking brakes.
Park on level ground and drain off air pressure before adjusting.
Park on level ground, chock the wheels, and release the parking brakes.

3. The braking power of the spring brakes
Increases when the service brakes are hot.
Depends on the service brakes being in adjustment.
Is not affected by the condition of the service brakes.

4. Water should be drained from the compressed air tanks
Because the low boiling point of water reduces braking power.
To keep from fouling the air compressor oil.
Because water can freeze in cold weather and cause brake failure.

5. Which of these is the most important thing to remember about emergency braking?
If the wheels are skidding, you cannot control the vehicle.
Never do it without downshifting first.
Disconnecting the steering axle brakes will help keep your vehicle in a straight line during emergency braking.

6. Air brake-equipped vehicles have
An air use gauge.
Backup hydraulic system.
An air supply pressure gauge.

7. You should brake in a way that will keep your vehicle in a straight line and allow you to turn if it becomes necessary. You can use the
“controlled braking” method.
“stab braking” method.
Either of the above methods.

8. When you pull hard on a slack adjuster, if its free play is more than _______, the slack adjuster will need to be adjusted.
1/4 inch
1/2 inch
1 inch

9. The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than
2 psi in 45 seconds.
3 Psi in one minute.
1 psi in one minute.

10. What is a dual air brake system?
A Two-brake system: One brake operates the front brakes, and one operates the back brakes.
A two-brake system: One brake for daytime driving and one for nighttime driving.
A Two-brake system, one brake for each side of the vehicle.

11. The braking power of the spring brakes
Is not affected by the condition of the service brakes.
Increases when the service brakes are hot.
Depends on the service brakes being in adjustment.

12. When you are going down a long or steep grade after selecting the proper gear, the proper method of braking is to brake until your speed is about __ miles per hour below your “safe” speed and then release your brakes.
15
5
10

13. The modulating control valve allows you to control the
Amount of pressure in the brake system.
Spring brakes.
Front brakes.

14. During normal driving, spring brakes are usually held back by
Air pressure.
Springs.
Bolts and braces.

15. The parking or emergency brakes of trucks or buses can legally be held on by _____ pressure.
Spring
Air
Fluid

16. It is accepted that too much heat caused by using your brakes too often can also cause
The brake linings to split.
Brake fade or failure.
The modulated control valve to wear out.

17. Before you drive a truck or bus with a dual air brake system, the pressure in each air brake system should be at least ___ psi.
120
100
80

18. It is not safe to drive a vehicle that has brake drums with cracks that are longer than ____ of the width of the friction area.
1/2
1/4
5/16

19. Excessive use of the service brakes results in overheating, which can lead to
Increased contact between the brake drums and the brake linings.
Improper adjustment of S-cam.
Expansion of the brake drums.

20. The modulating control valve allows you to control the
Amount of pressure in the brake system.
Front brakes.
Spring brakes.