CDL manual Flashcards
What is the minimal amount of tread depth on the front tires?
4/32
What is the minimum amount of tread depth on the rear (all other) tires?
2/32
How much play can a steering wheel have?
10 degrees, 2 inches at the rim of 20 inch steering wheel can make it hard to steer.
Aire pressure should build from 50 to 90 psi within how long?
3 minutes
The build air pressure governer usually cuts out at what psi?
120-140
What are the three different air braking systems?
Service brake, parking brake, and emergency brake
The service break does what?
Applies and releases the brakes when you use the brake pedal during normal driving.
What does the parking break do?
Applies and releases the parking brakes when you use the parkin brake control.
What does the service brake do?
Uses parts from the emergency and service brakes to stop the vehicle in a brake system failure
When the air pressure rises to the “cut out” level, the governor stops the compressor from pumping. What is the PSI?
Around 125 PSI
When the tank pressure drops to the cut in level pressure, the governor allows the compressor to start pumping again. What is the PSI?
Around 100 PSI
The safety valve on the air tank for the air brakes is set to open at what psi?
150 psi
A warning light comes on before the air pressure in the tanks falls below what PSI?
60 psi
The brake will pop at what PSI?
20-45 (typically 20-30)
Pumping by the air compressor should start at what PSI and stop out at
100 psi and 125 psi
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?
Less than 2 psi in one minute for single vehicles and 3 psi in one minute for combination vehicles.
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?
More than 3 pounds in one minute (single vehicles) or 4 pounds in one minute (combination vehicles)
The low air pressure warning signal must come on before the pressure drops to less than what in the air tank?
60 psi
When the engine is at operating RPMs, the pressure should build up from 85 to 100 within how long?
45 seconds
How do you test the service brakes?
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.
When coming to stopping distance there can be a delay or how long for air to flow through the lines?
one half second or longer
Total stopping distance equals what?
Perception distance + Reaction Distance + Brake Lag Distance + Braking Distance
Air brake lag distance at 55 mph on dry pavement adds about how many feet?
32 feet
