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How do brakes work on a long, steep downgrade?
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When should you use the parking brake?
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AB CDL
| Question | Answer |
|---|---|
| How do brakes work on a long, steep downgrade? | They work as a supplement to the braking effect of your engine |
| When should you use the parking brake? | Every time you leave your vehicle, with a few exceptions |
| The purpose of a supply pressure gauge is: | To tell you how much air is in the tank |
| Which of the following is NOT part of the drum brake? | Safety Valve |
| Which of the following can cause brakes to fade or fail? | All of the above. |
| Which of the following are true about a dual air brake system? | All are true |
| Which of the following is NOT part of the air brake system? | Radio signal system |
| If the air tanks are not drained, | Your brakes may fail because of water freezing |
| The tractor protection valve: | Provides the air supply for the brake system, will close if you apply the parking brakes, will close automatically if the air supply drops to a certain level |
| Which vehicles must have low air pressure warning signals? | All vehicles with air brakes currently in operation |
| Which of the following should you do before leaving your vehicle unattended? | Set the parking brakes, chock the wheels, remove the keys |
| An antilock braking system (ABS): | Activates when your wheels are about to lock up |
| After the initial drop, the maximum acceptable leakage rates per minute are: | |
| 3 psi for single vehicles, 4 psi for combination vehicles | |
| Under which conditions are front wheel brakes good? | All weather conditions |
| Which of the following is NOT part of the braking process when you’re driving a tractor-trailer combination vehicle with an ABS? | You should drive faster so that you will be able to keep the trailer and tractor in sight |
| What is the best way to test your vehicle’s low air pressure warning signal? | With the engine off, step on and off the brake pedal to lower the air pressure below 60 psi |
| Which of the following will be true about your brake function if your ABS fails? | You will still have normal brake function and will need to get the ABS repaired soon |
| How would you check your truck’s slack adjusters? | Use gloves and pull hard on each slack adjuster you can reach |
| At what measurement is the safety valve USUALLY set to open? | 150 psi |
| How can you tell if your vehicle is equipped with an ABS? | Check if the vehicle was manufactured after 1998 |
| Slack adjusters are: | Between the push rod and S-cam on drum brakes, part of the air brake system that is used to adjust the brakes, and between the power screw and push rod on disc brakes |
| What is the best way to test of your vehicle’s spring brakes come on automatically? | All are correct |
| Spring brakes are: | Brakes that come on automatically on a truck or tractor when the psi drops too low, not going to take full effect until your psi drops to a certain range (20-30 psi), made up of powerful springs that are held back by air pressure while you are driving |
| The braking power of the spring brakes: | Depends on whether the service brakes are in proper adjustment |
| The driver must be able to see a low pressure warning, which comes on before pressure in the service air tank falls below: | 60 psi |
| The safety valve is set to automatically reduce pressure at: | 150 psi |
| The SERVICE brake system applies: | The brakes when you depress the brake pedal during normal driving |
| The application pressure gauge shows the amount of air pressure: | That you apply to the brakes |
| The air compressor governor controls: | When air is pumped into the air storage tanks |
| The stop light switch: | Turns on the brake lights when you brake |
| Your vehicle has a dual air brake system. If a low air pressure warning comes on for just one of the two systems, what should you do? | Stop and park safely. Continue only after the system has been fixed. |
| If your vehicle has a properly functioning dual air brake system and medium-sized air tanks, the air pressure should build from 85 to 100 psi within ____ seconds. | 45 |
| The braking system that applies the brakes when the driver presses the brake pedal is the _____ brake system. | Service |
| On a long or steep downgrade, once you have reached your “safe” speed, brake until you are traveling: | 5 mph slower |
| The air loss rate for a straight truck or bus with the engine off and the brakes on should not be more than: | 3 psi in one minute |
| On large, heavy vehicles, the parking brake or emergency brakes must be held on by something that cannot leak away, such as: | Spring pressure |
| In a vehicle equipped with air brakes, the brake pedal: | Controls the air pressure applied to the service brakes |
| The most common type of foundation brake found on vehicles with air brakes is the: | S-cam drum brake |
| In the event of a brake system failure, the emergency brake system uses _____ to stop the vehicle. | Parts of the service brakes and parking brakes |
| The S-cam: | Forces the brake shoes against the inside of the brake drum |
| At 55 mph on dry pavement, the air brake lag distance is about: | 32 feet |
| What is the supply pressure gauge used for? | To show how much pressure is in the air tanks |
| The parking brake control: | Let’s the air out of the brake chambers |
| With S-cam drum brakes, when the brake chamber fills with air, air pressure pushes the push rod out, moving the ____ and thus rotating the _____. | Slack adjusters, brake camshaft |
| The modulating control valve allows you to control the: | Spring brakes |
| If your truck or bus has dual parking control valves, you can use air pressure from a separate tank to: | Release the spring emergency/parking brakes |
| To make an emergency stop with the “stab braking” method, you should: | Depress the brake pedal as hard as you can, release the brakes when the wheels lock, and apply the brakes again when the wheels start to roll. |
| If the air compressor should develop a leak, what will keep air in the tanks? | The one-way check valve |
| Excessive use of the service brakes may result in overheating, which can lead to : | Expansion of the brake drums |
| The low air pressure warning signal will come on before the pressure in the air tanks falls below: | 55 psi |
| When you pull hard on a slack adjusters, if it has more than ____ of free play, the slack adjusters may need adjustment. | 1 inch |
| To apply the parking brakes under normal conditions: | Let the air out of the brake chambers |
| The air compressor will stop pumping air into the air tanks at ___ psi. | 125 |
| If your truck or bus has dual parking control valves, you can use air pressure from a separate tank to: | Release the spring brakes |
| Your vehicle has a dual air brake system. One of the systems loses air pressure. What will happen? | Either the front or rear brakes will not be fully operational. |
| If the spring brakes are on, when should you push the brake pedal? | Never. |
| Tractor and straight truck spring brakes will come fully on when the air pressure drops to a range of: | 20 to 45 psi |
| A typical air brake system is fully charged at: | 125 psi |
| During normal driving, spring brakes are usually held back by: | Air pressure |
| If the low air pressure signal is not working: | It may lead to sudden emergency braking in a single-circuit air system |
| In which of the following situations should you NOT apply the parking brakes? | If the brakes are very hot. |
| When you apply the brake pedal, the brake shoes and linings are pressed against the : | Brake drum |
| When you press the brake pedal, | Compressed air enters the brake chambers |
| Under ideal conditions, the average driver of a truck or bus equipped with air brakes and traveling at 55 mph would require what stopping distance? | More than 400 feet |
| If you need to stop quickly and your vehicle lacks antilock brakes, you can use: | Controlled or stab braking |
| Which of the following is the most important thing about hard braking? | Don’t lock the wheels for longer than an instant |
| A converter dolly with ABS is required to have: | A yellow lamp on the left side |
| During your final air brake check, if the air pressure does not build up fast enough: | The air pressure may drop too low during driving |
| To correct a drive-wheel braking skid, you should : | Stop braking, turn quickly, and counter steer |
| To test the air service brakes: | Brake firmly while slowly moving forward |
| Why is it called an “S-cam”? | It is shaped like the letter “S” |
| How do you adjust a manual slack adjusters? | Turn the adjusting nut to move the end of the slack adjusters toward the air chamber until the nut stops turning. Then turn the nut the other way to move the brake shoes away from the inside of the brake drum |
| In controlled braking, you: | Brake in a straight line |
| To test the static air leakage rate, you should: | Turn off the engine, release the parking brake, and let the system settle |
| Before starting down a hill, you should be in the proper gear: | So you only have to apply the brake just hard enough to feel a definite slowdown |
| During your walk-around inspection, check the brake drums to be sure that no cracks are longer than ____ the width of the friction area. | 1/2 |
Created by:
zedoc43