Georgia CDL: Air Brakes Practice Test

Not quite. The answer is Overheating, low air pressure, and not relying on the engine braking effect

Brake fade and failure are usually due to incorrect use of the brakes that causes overheating. This may be caused by incorrect brake adjustment, not enough reliance on engine braking, excessive use of the service brakes, another mechanical factor, or human error. Air brakes will also fail if air pressure drops too low.

Not quite. The answer is slack adjuster; brake camshaft

To apply the S-cam drum brakes, air is let into each brake chamber. Air pressure pushes the pushrod out, moving the slack adjuster, thus rotating the brake camshaft. As the S-cam on the camshaft rotates, it forces the brake shoes against the inside of the brake drum.

Not quite. The answer is Yes, so keep them on the "normal" setting.

Front wheel braking is good under all conditions. Tests have shown front wheel skids from braking are not likely even on ice. Make sure the control is in the “normal” position to have normal stopping power.

Not quite. The answer is one-half

During your walk-around inspection, check the brake drums or brake discs to be sure that no cracks are longer than half the width of the friction area.

Not quite. The answer is Don't lock the wheels for longer than an instant.

When braking hard, don't lock the wheels for longer than an instant (which is done in stab braking). If the wheels stay locked, they will lose the grip of the road and your vehicle may skid or even jackknife.

Not quite. The answer is brake in a straight line.

In controlled braking, you brake as hard as you can without locking the wheels. As you do this, keep your vehicle going relatively straight.

Not quite. The answer is compressed air enters the brake chambers.

Pressing down on the brake pedal lets air into each brake chamber, forcing the brake pads against the inside of the drum (or the rotor for disc brakes).

Not quite. The answer is your brakes may fail because of water freezing.

Oil and water can start to collect at the bottom of an air tank, which can lead to brake failure. Unless your vehicle automatically drains the air tanks, you should drain them at the end of each working day so the moisture and oil will not freeze or coagulate and cause your brakes to fail.

Not quite. The answer is 100 psi.

A dual air brake system has two separate air brake systems. Typically, the primary system operates the brakes on the rear axle(s), and the secondary system operates the brakes on the front axle (and possibly one rear axle). Before driving a vehicle with a dual air brake system, let the air compressor build up a minimum of 100 psi pressure in each of the two brake systems.

Not quite. The answer is If the brakes are very hot

If the brakes are too hot, avoid using the parking brakes because the heat may warp and damage the brakes. Also avoid using the parking brakes if they are wet and at risk of freezing. If the parking brakes freeze, your vehicle will be immobilized. In both of these situations, use wheel chocks instead.

Not quite. The answer is Park on level ground, turn off the parking brakes, and pull hard on each slack adjuster.

To check the slack adjusters, try to pull on them manually while wearing gloves. If there is an inch or more of "give," then there is an issue and they should be fixed.

Not quite. The answer is release the spring brakes.

When main air pressure is lost, the spring brakes come on and stop your vehicle. Some vehicles such as buses have a separate air tank with enough air to release the spring brakes in case the vehicle must be moved temporarily in an emergency. (The tank holds only enough air to do this a few times, however.) You control this action with the dual parking control valve.

Not quite. The answer is 150 psi.

The safety valve, which protects the system from excessive pressure, is usually set to open when the system reaches 150 psi.

Not quite. The answer is Pressure-protection valve

Various auxiliary air systems, such as air suspension and the driver and passenger air seats, usually get their air from the service tanks of the air braking system. To prevent the tanks from losing air in the event of a leak or failure in an auxiliary air system, a pressure-protection valve is installed between each auxiliary air system and the service tank. If tank pressure drops below a preset level, the pressure-protection valve will close to stop any more air from flowing to the auxiliary air system.

Not quite. The answer is All of the above

Brake fade and failure are usually due to incorrect use of the brakes that causes excess heat. This may be caused by incorrect brake adjustment, not enough reliance on engine braking, excessive use of the service brakes, another mechanical factor, or human error.

Not quite. The answer is You will still have normal brake function and will just need to get the ABS repaired soon.

Losing the ABS function does not change the basic parts of your truck, so you will still have the same brakes that you have always had. Simply use them and get the ABS repaired as soon as possible. There is no need to panic unless your system shows other and more serious warnings.

Not quite. The answer is 3 psi per minute.

After the initial drop, the maximum acceptable leakage rates with the service brakes on are 3 psi per minute for single vehicles and 4 psi per minute for combination vehicles. If the leakage rate is higher, check for leaks and correct them.

Not quite. The answer is Whenever your vehicle is parked

You should always use your parking brake except when the brakes are very hot or they are wet and at risk of freezing.

Not quite. The answer is service

Air brakes are really three braking systems in one: the emergency brake, the parking brake, and the service brake. As these names suggest, when you depress the brake pedal in normal driving, it's the service brake system that applies the brakes.

Not quite. The answer is You should drive faster so that you will be able to keep the trailer and tractor straight.

When driving a tractor-trailer combination vehicle that has ABS, drive the same way that you always have. Do not drive any differently just because of ABS. Only use the braking necessary to keep control, pay attention when you slow down, and brake the same way regardless of what you're driving. Never speed up unless it is part of the safe driving process already.