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California CDL Air Brakes Test Practice Questions - California CDL Air Brakes Knowledge Test Exam
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Question
1
of 25
QUESTION 1 / 25
In the California CDL Air Brakes test, what component compresses air for the air brake system?
Choose one answer below.
A
The air dryer
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B
The air compressor
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C
The brake chamber
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D
The slack adjuster
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QUESTION 2 / 25
What is the typical air compressor governor cut-out pressure range?
Choose one answer below.
A
60 to 80 psi
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B
100 to 125 psi
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C
125 to 140 psi
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D
150 to 175 psi
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QUESTION 3 / 25
At what pressure does the air compressor governor typically cut IN to resume pumping?
Choose one answer below.
A
60 to 80 psi
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B
100 to 125 psi
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C
125 to 140 psi
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D
145 to 150 psi
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QUESTION 4 / 25
What is the purpose of the air dryer in the brake system?
Choose one answer below.
A
To cool the air before storage
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B
To remove moisture and oil before air reaches the tanks
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C
To increase compressed air pressure
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D
To warn the driver of low pressure
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QUESTION 5 / 25
What is the function of the wet tank (supply or service reservoir)?
Choose one answer below.
A
It cools brake fluid
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B
It is the first storage tank where moisture collects before air moves to the other tanks
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C
It supplies air only to the trailer
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D
It activates the parking brakes
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QUESTION 6 / 25
At what pressure does the safety valve in the supply tank typically open to release excess air?
Choose one answer below.
A
100 psi
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B
125 psi
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C
150 psi
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D
200 psi
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QUESTION 7 / 25
What is the role of the foot valve (also called the treadle or service brake valve)?
Choose one answer below.
A
It locks the parking brake
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B
It supplies air to the brake chambers in proportion to how hard the driver presses the pedal
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C
It drains water from the tanks
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D
It controls the trailer air supply
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QUESTION 8 / 25
What does the brake chamber do?
Choose one answer below.
A
Stores compressed air for emergencies
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B
Converts air pressure into mechanical force through a pushrod
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C
Cools brake drums during use
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D
Acts as a backup for the parking brake
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QUESTION 9 / 25
What is the role of the slack adjuster on an S-cam brake?
Choose one answer below.
A
It cushions the impact of hard braking
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B
It transfers force from the pushrod to the S-cam and can be adjusted to compensate for lining wear
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C
It bleeds water from the system
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D
It limits maximum air pressure
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QUESTION 10 / 25
What does the S-cam do in an S-cam drum brake?
Choose one answer below.
A
It releases air from the lines
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B
It rotates between the brake shoes, forcing them outward against the drum
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C
It cools the brake drum
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D
It activates the low-pressure warning
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QUESTION 11 / 25
How are spring (parking) brakes held in the released position?
Choose one answer below.
A
By engine vacuum
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B
By a hydraulic line
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C
By air pressure applied against the spring
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D
By a mechanical lock that the driver releases
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QUESTION 12 / 25
What is the shape and color of the parking brake control knob in most modern CMVs?
Choose one answer below.
A
A red 8-sided (octagonal) knob
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B
A yellow diamond-shaped knob
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C
A green round knob
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D
A blue square knob
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QUESTION 13 / 25
What is the shape and color of the trailer air supply control on a tractor?
Choose one answer below.
A
A yellow diamond knob
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B
A red 8-sided (octagonal) knob
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C
A blue triangular knob
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D
A green round knob
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QUESTION 14 / 25
What is a dual air brake system?
Choose one answer below.
A
A system that uses two compressors
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B
A system with two completely separate air systems (primary and secondary), each controlling brakes on different axles
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C
A system that uses both air and hydraulic fluid
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D
A system with air-cooled drums
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QUESTION 15 / 25
At what pressure must the low air pressure warning device activate at the latest?
Choose one answer below.
A
At 30 psi
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B
Between 55 and 75 psi
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C
At 90 psi
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D
At 120 psi
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QUESTION 16 / 25
While driving, the low air pressure warning light comes on. What should you do?
Choose one answer below.
A
Continue to your destination but watch the gauge
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B
Bring the vehicle to a safe stop as soon as possible and find the problem
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C
Apply the parking brake while still moving
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D
Pump the brake pedal to build pressure
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QUESTION 17 / 25
How often should air tank drain valves be operated to remove water and oil?
Choose one answer below.
A
Once a year
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B
After every long trip only
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C
Daily
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D
Only when the warning light comes on
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QUESTION 18 / 25
What is the maximum allowable air loss rate for a single vehicle with the brakes released (static leak rate)?
Choose one answer below.
A
1 psi per minute
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B
2 psi per minute
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C
3 psi per minute
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D
4 psi per minute
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QUESTION 19 / 25
What is the maximum allowable air loss rate for a combination vehicle with the brakes released?
Choose one answer below.
A
1 psi per minute
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B
2 psi per minute
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C
3 psi per minute
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D
5 psi per minute
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QUESTION 20 / 25
What is the maximum allowable air loss rate for a single vehicle with the brakes APPLIED (applied leak rate)?
Choose one answer below.
A
2 psi per minute
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B
3 psi per minute
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C
4 psi per minute
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D
5 psi per minute
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QUESTION 21 / 25
In the California CDL Air Brakes test, what is the maximum allowable air loss rate for a combination vehicle with the brakes APPLIED?
Choose one answer below.
A
2 psi per minute
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B
3 psi per minute
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C
4 psi per minute
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D
6 psi per minute
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QUESTION 22 / 25
During the air brake pre-trip inspection, how do you test the low air pressure warning device?
Choose one answer below.
A
Start the engine and watch the gauge
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B
Build air pressure to governor cut-out, shut off the engine, turn the key to the on position, and fan the brakes until the warning activates
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C
Apply the parking brake and listen for the alarm
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D
Drain the wet tank only
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QUESTION 23 / 25
During the air brake pre-trip, how do you test that the spring brakes apply automatically?
Choose one answer below.
A
Apply the foot brake hard while driving
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B
Continue fanning the brakes until air pressure drops far enough; the spring brakes should apply between roughly 20 and 45 psi
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C
Pull the parking brake at 55 psi
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D
Drain the secondary tank only
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QUESTION 24 / 25
In normal stops with air brakes, you should:
Choose one answer below.
A
Stab the pedal hard, then release
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B
Apply the brakes firmly and steadily until you slow enough to safely shift to neutral or a lower gear
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C
Apply the parking brake
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D
Pump the pedal rapidly
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QUESTION 25 / 25
What is controlled braking in an emergency stop with air brakes?
Choose one answer below.
A
Pressing the pedal as hard as possible and holding it
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B
Applying the brakes as hard as you can without locking the wheels, then releasing slightly if wheels lock
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C
Using only the parking brake
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D
Pumping the pedal rapidly
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