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1 / 40
A. Perception distance.
B. Brake lag distance.
C. Reaction distance.
With air brakes there is an added delay or Brake Lag. This is the time required for the brakes to work after the brake pedal is pushed. With hydraulic brake, the brakes work instantly. With air brakes it takes a little time, one half second or more, for the air to flow through the lines to the brakes.
2 / 40
A. the brakes to fade.
B. the modulating control valve to wear out.
C. the brake linings to split.
Brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect.
3 / 40
A. Disc brakes
B. Wedge drum
C. S-cam brake
Wedge brakes and disc brakes are less common than s-cam brakes.
4 / 40
A. 23
B. 32
C. 50
The air brake lag distance at 55 mph on dry pavement adds about 32 feet.
5 / 40
A. Use the full power of the brakes and lock them.
B. Stay in a straight line and can steer.
C. Can steer hard while braking hard.
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 or the "stab braking" method.
6 / 40
A. Release the brake when you are 5 mph below your "safe" speed.
B. Use stab braking.
C. Begin braking when you are 10 mph above your safe speed.
Snub braking method is used for steep downhill grades, in this method apply the brakes just hard enough to feel a definite slowdown. When your speed has been reduced to approximately five mph below your "safe" speed, release the brakes. When your speed has increased to your "safe" speed, repeat.
7 / 40
A. Spring pressure
B. Air pressure
C. Fluid pressure
All trucks, truck tractors, and buses must be equipped with emergency brakes and parking brakes. They must be held on by mechanical force because air pressure can eventually leak away. Spring brakes are usually used to meet these needs.
8 / 40
A. air pressure.
B. bolts and braces.
C. springs.
Parking or emergency brakes must be held on by mechanical force because air pressure can eventually leak away. Spring brakes are usually used to meet these needs. When driving, powerful springs are held back by air pressure.
9 / 40
A. Up shift.
B. Adjust the brake pedal for more travel.
C. Stop and safely park as soon as possible.
When the low air pressure warning light and buzzer first come on, bring the vehicle to a safe stop right away, while you can still control the brakes.
10 / 40
A. 60 psi
B. 40 psi
C. 20 psi
Low air warning devices (buzzer, light, flag) should activate before air pressure drops below 60 psi or level specified by the manufacturer.
11 / 40
A. charge the air system and leave the engine running.
B. leave the engine running and release the parking brake.
C. turn off the engine, release the parking brake, and let the system settle.
With a fully-charged air system (typically 125 psi), turn off the engine, release the parking brake (push in); and time the air pressure drop.
12 / 40
A. ABS is still optional.
B. Check if the vehicle was manufactured after 2000.
C. Check if the vehicle was manufactured after 2010.
D. Check if the vehicle was manufactured after 1998.
The Department of Transportation requires that ABS be on: air brake vehicles built on or after March 1, 1998.
13 / 40
A. not going to take full effect until your psi drops to a certain range, typically 20 to 30 psi.
B. all of the above.
C. made up of powerful springs that are held back by air pressure while you are driving.
D. brakes that come on automatically on a truck or tractor when the psi drops too low.
Spring brakes are an important backup system: powerful springs that automatically apply the brakes if they sense that air pressure has been lost for some reason, such as a leak. They will also apply the brakes if the psi gets too low, although ideally, you should take control of your brakes before that happens.
14 / 40
A. The speed of the air compressor.
B. When air is pumped into the air tanks.
C. Air pressure applied to the brakes.
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.
15 / 40
A. You should use only the braking necessary to stay safely in control.
B. Brake the same way no matter what you're driving: a vehicle with ABS, a vehicle with a trailer, or something else.
C. You should drive faster so that you will be able to keep the trailer and tractor straight.
D. When you slow down, you should monitor your tractor and trailer and ease off the brakes to keep control.
When you drive a vehicle with ABS, you should brake as you always have. In other words: use only the braking force necessary to stop safely and stay in control; brake the same way regardless of whether you have ABS on the bus, tractor, the trailer, or both; as you slow down monitor your tractor and trailer and back off the brakes if it is safe to do so to stay in control.
16 / 40
A. All of the above
B. Excessive use of the service brakes
C. Not relying enough on engine braking
D. Brakes being out of adjustment
Brakes can fade or fail from excessive heat caused by using them too much and not relying on the engine braking effect. Brake fade is also affected by adjustment.
17 / 40
A. parts of the service brakes and parking brakes
B. only the parking brakes
C. only the service brakes
The emergency brake system uses parts of the service and parking brake systems to stop the vehicle in a brake system failure.
18 / 40
A. hydraulic fluid
B. natural gas
C. compressed air
Air brakes use compressed air to make the brakes work. Air brakes are a good and safe way of stopping large and heavy vehicles, but the brakes must be well maintained and used properly.
19 / 40
A. All of the above are true.
B. One system is called the "primary" system and the other one is called the "secondary" system.
C. It uses a single set of brake controls.
D. Usually, one system operates the front axle and the other one operates the rear axle.
Most heavy-duty vehicles use dual air brake systems for safety. A dual air brake system has two separate air brake systems, which use a single set of brake controls. One system or primary system typically operates the regular brakes on the rear axle or axles. The other or secondary system operates the regular brakes on the front axle and possibly one rear axle.
20 / 40
A. increased contact between the brake drums and the brake linings.
B. improper adjustment of the S-cams.
C. expansion of the brake drums.
Brake fade results from excessive heat causing chemical changes in the brake lining, which reduce friction, and also causing expansion of the brake drums.
21 / 40
A. Pump the brake pedal rapidly and lightly.
B. Brake as hard as you can, get off the brakes when the wheels lock, get back on the brakes when the wheels start rolling again.
C. Brake hard until the wheels lock, and then get off the brakes for as much time as the wheels were locked.
Stab braking means that you: apply your brakes all the way, and release brakes when wheels lock up. As soon as the wheels start rolling, apply the brakes fully again.
22 / 40
A. After every working day.
B. After every four hours of service.
C. Once a week.
If your vehicle does not have automatic air tank drains, drain your air tanks at the end of each working day to remove moisture and oil. Otherwise, the brakes could fail.
23 / 40
A. Increases when the service brakes are hot.
B. Is not affected by the condition of the service brakes.
C. Depends on the adjustment of the service brakes.
The braking power of spring brakes depends on the brakes being in adjustment. If the brakes are not adjusted properly, neither the regular brakes nor the emergency/parking brakes will work right.
24 / 40
A. To release the brakes.
B. To apply the brakes.
C. To test the slack adjusters.
When you push the brake pedal, air is let into each brake chamber. Air pressure pushes the rod out, moving the slack adjuster, thus twisting the brake camshaft. This turns the s-cam forcing the brake shoes away from one another and presses them against the inside of the brake drum.
25 / 40
A. On tractor-trailer vehicles, continue to step on and off the brake pedal until the parking brake valve pops out.
B. Continue to step on and off the brake pedal until the manufacturer's low psi specification is met for spring brakes to deploy.
C. All of the above are correct.
D. On single vehicles, continue to step on and off the brake pedal until the parking brake valve pops out.
On both tractor-trailers and single vehicles, to test whether the spring brakes will come on automatically, use the same method you use for testing the low air pressure warning signal: Step on and off the brake pedal, this time until you reach an even lower psi reading and the parking brake valve closes or pops out.
26 / 40
A. 150 psi.
B. 125 psi.
C. 75 psi.
Pumping by the air compressor should start at about 100 psi and stop at about 125 psi.
27 / 40
A. the air pressure may drop too low during driving.
B. the alcohol evaporator may be low.
C. have the problem fixed after your trip is over.
If air pressure does not build up fast enough, your pressure may drop too low during driving, requiring an emergency stop. Don't drive until you get the problem fixed.
28 / 40
A. Emergency brakes.
B. S-cam brakes.
C. Foot brakes.
Air brakes are really three different braking systems: service brake, parking brake, and emergency brake.
29 / 40
A. Good weather only
B. Wet or icy conditions only
C. None
D. All weather conditions
Front wheel brakes have been shown to be ideal under all weather and driving conditions. Front wheel braking is unlikely to cause a skid even on icy roads.
30 / 40
A. Remove the keys.
B. Set the parking brakes.
C. Do all of the above.
D. Chock the wheels.
Never leave your vehicle unattended without applying the parking brakes or chocking the wheels. Your vehicle might roll away and cause injury and damage
31 / 40
A. 125
B. 100
C. 150
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.
32 / 40
A. A supply pressure gauge.
B. An air use gauge.
C. At least two brake heaters.
All vehicles with air brakes have a pressure gauge connected to the air tank. If the vehicle has a dual air brake system, there will be a gauge for each half of the system.
33 / 40
A. activates when your wheels are about to lock up.
B. increases your normal braking capability.
C. decreases your normal braking capability.
D. shortens your stopping distance.
ABS is a computerized system that keeps your wheels from locking up during hard brake applications.
34 / 40
A. 45
B. 20
C. 60
When the engine is at operating rpms, the pressure should build from 85 to 100 psi within 45 seconds in dual air systems. If the vehicle has larger than minimum air tanks, the buildup time can be longer and still be safe.
35 / 40
A. Eliminate the need for daily tank draining.
B. Reduce the risk of ice in air brake valves in cold weather.
C. Rid the wet tank of alcohol that condenses and sits at the bottom.
Some air brake systems have an alcohol evaporator to put alcohol into the air system. This helps to reduce the risk of ice in air brake valves and other parts during cold weather. Daily air tank drainage is still needed to get rid of water and oil.
36 / 40
A. It will slow your truck to a halt and force you to pull over.
B. You will still have normal brake function and will just need to get the ABS repaired soon.
C. It may cause problems with other mechanical systems and possibly pose a huge fire risk.
D. You will have no brake function and your truck will be out of control.
Without ABS you still have normal brake functions. Drive and brake as you always have.
37 / 40
A. Emergency brake system.
B. Parking brake system.
C. Service brake system.
The service brake system applies and releases the brakes when you use the brake pedal during normal driving.
38 / 40
A. your left side brake will cease to operate.
B. you will drive too quickly.
C. your brakes may fail because of water freezing.
D. your transmission fluid may drain out.
Compressed air usually has some water and some compressor oil in it, which is bad for the air brake system. For example, the water can freeze in cold weather and cause brake failure.
39 / 40
A. compressed air enters the brake chambers.
B. compressed air is released from the air tanks.
C. compressed air is released from the brake chambers.
When you push the brake pedal, air is let into each brake chamber.
40 / 40
A. Should not be used because it is very unsafe.
B. A spring-loaded valve that will let you put on the brakes on slowly if the service brakes fail.
C. There is no such thing.
In some vehicles, a control handle on the dash board may be used to apply the spring brakes gradually. This is called a modulating valve. It is spring loaded, so you have a feel for the braking action. The more you move the control lever, the harder the spring brakes come on. They work this way, so you can control the spring brakes if the service brakes fail.
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