Texas CDL: Air Brakes Practice Test

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 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 about 250 °C.

Brakes are designed to withstand quite a lot of heat. The brake components can withstand temperatures up to about 250° C (482 °F) under hard braking.

Not quite. The answer is Do all of the above.

To ensure that your vehicle will be safe when you leave it unattended, apply the parking brakes and chock the wheels. Removing the keys is a simple safety tip for any vehicle, even a passenger car.

Not quite. The answer is one-half

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

Not quite. The answer is the emergency brake system.

The system that uses parts of the service and parking brake systems to stop the vehicle in a brake system failure is called the emergency brake system.

Not quite. The answer is Evacuate the air from the brake chambers.

In today's CMVs, you apply or release the parking brakes with the parking brake control on the dashboard. This is a diamond-shaped, yellow, push-pull control knob. To apply the parking brakes, pull out the knob to evacuate the air from each brake chamber, which will cause the spring brakes to come on.

Not quite. The answer is the brakes when you depress the brake pedal during normal driving.

Air brakes are actually three braking systems in one: the emergency brake, the parking brake, and the service brake. As these terms 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 Radio signal system

The air brakes are made up of three systems: the service brake, the parking brake, and the emergency brake. Before your knowledge test, review the Texas Commercial Motor Vehicle Drivers Handbook to familiarize yourself with what each one does.

Not quite. The answer is They help maintain correct pushrod stroke.

An automatic slack adjuster automatically compensates for normal brake lining wear by adjusting pushrod stroke. Automatic slack adjusters should not normally require manual adjustment of pushrod stroke. However, they still require lubrication at regular intervals.

Not quite. The answer is lets the air out of the brake chambers.

When you apply the parking brake control, air is released from the brake chambers, causing the springs to apply the brakes and hold your vehicle in place.

Not quite. The answer is Every time you leave your vehicle, with a few exceptions

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 It 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 service brakes nor the emergency or parking brakes will work right.

Not quite. The answer is 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.

Not quite. The answer is Drive normally until the ABS is repaired.

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.

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 the service brake valve and the parking brake valve.

A spring parking brake can exert a force of up to 2,000 pounds, and a Type 30 service brake chamber can exert a force of 3,000 pounds or more. If both forces were applied at the same time (which is called compounding the service and parking brakes), the combined force could damage parts of the braking system. To prevent this, most modern commercial vehicles employ an anti-compounding valve. One input port of this valve is connected to the service brake valve (foot valve), and another input port is connected to the parking brake valve (yellow knob). Suppose you set the parking brakes by pulling out the yellow knob. That valve will send air to the anti-compounding valve. If you also press the brake pedal, the foot valve will also send air to the anti-compounding valve. Then the anti-compounding valve will partially release the parking brakes by the same amount of force that the foot valve has applied.

Not quite. The answer is 125

The air compressor will start pumping air into the air tanks at about 100 psi and stop at about 125 psi. This action is controlled by the air compressor governor.

Not quite. The answer is To show how much pressure is in the air tanks.

The air supply pressure gauge is connected to the air tank (or possibly to both tanks in a dual air tank system). It shows how much air pressure is in the air tanks.

Not quite. The answer is braking effect of the engine.

Going down a hill, you should keep your engine in a low gear to keep your speed low, and use the air brakes as a supplemental tool to slow down.