Air Brakes

Question 1

What are the different types of braking systems?

Answer 1

Service brake, parking brake, and emergency brake

Question 2

What are the cut-out and cut-in levels?

Answer 2

Cut-out is around 125 psi
Cut-in is around 100 psi

Question 3

What is an air compressor governor?

Answer 3

The governor controls when the air compressor will pump air into the air storage tanks. When air tank pressure rises to the cut-out level (around 125 psi), the governor stops the compressor from pumping air. When the tank pressure falls to the cut-in pressure (around 100 psi), the governor allows the compressor to start pumping again.

Question 4

What are the three brake types?

Answer 4

S-cam brakes, Wedge brakes, Disc brakes

Question 5

At what PSI does the low air pressure warning come on?

Answer 5

Before the air pressure in the tanks falls below 60 psi. (Or one-half the compressor governor cutout pressure on older vehicles.

Question 6

Tractor and straight truck spring brakes will come fully on when air pressure drops to what PSI?

Answer 6

20 to 44 PSI (typically 20 to 30 PSI)

Question 7

If your truck or bus has dual parking control valves it means that you can use pressure from a separate tank to:

Answer 7

Release the spring emergency/parking brakes to move a short distance

Question 8

A slack adjuster probably needs to be adjusted if it moves more than about:

Answer 8

1 Inch when you pull hard on it

Question 9

If you are driving down a steep downgrade and you have reached your safe speed of 40 miles per hour, you would apply the service brakes until your speed drops to:

Answer 9

35 mph

Question 10

For air brake systems in good condition, the air compressor should start pumping at about:

Answer 10

100 PSI

Question 11

If the spring brakes are on, when should you push the brake pedal?

Answer 11

NEVER

Question 12

Emergency controlled braking is when you:

Answer 12

Apply the brakes as hard as you can without locking the wheels

Question 13

What does the stop light switch do when you turn it on?

Answer 13

Turns on your brake lights to warn drivers behind you

Question 14

Modern air brake systems combine three different systems. They are the service, the parking, and the:

Answer 14

Emergency brakes

Question 15

During normal driving, spring brakes are usually help back by:

Answer 15

Air Pressure

Question 16

Emergency stab braking is when you:

Answer 16

Brake as hard as you can, release the brakes when the wheels lock, put on the brakes again when the wheels start rolling

Question 17

Total stopping distance for air brakes is longer than that for hydraulic brakes due to:

Answer 17

Brake lag distance

Question 18

Before driving a truck or bus with a dual air brake system, the pressure in each system should be at least:

Answer 18

100 PSI

Question 19

When the brakes are applied, the brake shoe (or linings) are pressed on the:

Answer 19

Brake drum or disc

Question 20

The modulating control valve allows you to control the:

Answer 20

Spring brakes

Question 21

The application pressure gauge shows how much pressure you:

Answer 21

Are applying to the brakes

Question 22

If your truck has a properly functioning dual air brake system and minimum size air tanks, the air pressure should build from 85 to 100 PSI within:

Answer 22

45 seconds