CDL manual

Question 1

What is the minimal amount of tread depth on the front tires?

Answer 1

4/32

Question 2

What is the minimum amount of tread depth on the rear (all other) tires?

Answer 2

2/32

Question 3

How much play can a steering wheel have?

Answer 3

10 degrees, 2 inches at the rim of 20 inch steering wheel can make it hard to steer.

Question 4

Aire pressure should build from 50 to 90 psi within how long?

Answer 4

3 minutes

Question 5

The build air pressure governer usually cuts out at what psi?

Answer 5

120-140

Question 6

What are the three different air braking systems?

Answer 6

Service brake, parking brake, and emergency brake

Question 7

The service break does what?

Answer 7

Applies and releases the brakes when you use the brake pedal during normal driving.

Question 8

What does the parking break do?

Answer 8

Applies and releases the parking brakes when you use the parkin brake control.

Question 9

What does the service brake do?

Answer 9

Uses parts from the emergency and service brakes to stop the vehicle in a brake system failure

Question 10

When the air pressure rises to the “cut out” level, the governor stops the compressor from pumping. What is the PSI?

Answer 10

Around 125 PSI

Question 11

When the tank pressure drops to the cut in level pressure, the governor allows the compressor to start pumping again. What is the PSI?

Answer 11

Around 100 PSI

Question 12

The safety valve on the air tank for the air brakes is set to open at what psi?

Answer 12

150 psi

Question 13

A warning light comes on before the air pressure in the tanks falls below what PSI?

Answer 13

60 psi

Question 14

The brake will pop at what PSI?

Answer 14

20-45 (typically 20-30)

Question 15

Pumping by the air compressor should start at what PSI and stop out at

Answer 15

100 psi and 125 psi

Question 16

When testing the air brake system, turn the engine off and release the parking brake and time the air pressure drop. The loss rate should be what?

Answer 16

Less than 2 psi in one minute for single vehicles and 3 psi in one minute for combination vehicles.

Question 17

With the air pressure built up to governor cutoff (120-140 psi) shut off the engine, chock your wheels, release the parking brake and fully apply the foot brake. Hold the foot brake for one minute. Check the air gauge to see if the air pressure drops how much?

Answer 17

More than 3 pounds in one minute (single vehicles) or 4 pounds in one minute (combination vehicles)

Question 18

The low air pressure warning signal must come on before the pressure drops to less than what in the air tank?

Answer 18

60 psi

Question 19

When the engine is at operating RPMs, the pressure should build up from 85 to 100 within how long?

Answer 19

45 seconds

Question 20

How do you test the service brakes?

Answer 20

Wait for normal air pressure, release the parking brake, move the vehicle forward slowly (about 5 mph) and apply the brakes firmly using the brake pedal.

Question 21

When coming to stopping distance there can be a delay or how long for air to flow through the lines?

Answer 21

one half second or longer

Question 22

Total stopping distance equals what?

Answer 22

Perception distance + Reaction Distance + Brake Lag Distance + Braking Distance

Question 23

Air brake lag distance at 55 mph on dry pavement adds about how many feet?

Answer 23

32 feet