Indiana CDL: Air Brakes Practice Test

Not quite. The answer is It disables the spring brake.

If your vehicle's service brakes fail, the emergency (spring) brakes will activate and stop your vehicle. Then to tow your vehicle for repairs, it will be necessary to disable the spring brakes. A technician can manually compress or "cage" the spring in each spring brake chamber. Obviously, the vehicle will be undrivable at this point because it will have no working brakes at all.

Not quite. The answer is stop braking, turn quickly, and countersteer.

To recover from a drive-wheel braking skid, first stop braking. The rear wheels will unlock and roll again so there will be no more tendency to slide sideways. Then quickly steer your vehicle back on course. You may find that your vehicle will overshoot and keep on turning, possibly skidding in the opposite direction. Countersteer to counteract this. Note: This maneuver takes some practice. You should become proficient in it before you actually need to use it.

Not quite. The answer is Park on level ground. Chock the wheels. Release the parking brake when you have enough air pressure. Shut off the engine. Repeatedly press and release the brake pedal.

To test whether the spring brakes come on, release the parking brake (all vehicles), release the tractor protection valve control (on combination vehicles), and turn off the engine while leaving the electrical power on to power the instrument panel. Then step on and off the brake pedal. The low air pressure warning signal should come on when the pressure has fallen below 55 psi. Continue stepping on and off the brake pedal until you reach about 20–45 psi, at which point the parking brake valve should close or pop out.

Not quite. The answer is a supply tank.

An Integrated Solution Air Dryer (AD-IS®) and Reservoir System provides an integrated air dryer, purge reservoir, governor, and a number of the charging valve components in a module. The air dryer is so efficient that a supply ("wet") tank is not needed. Instead, the AD-IS sends air directly to the primary and secondary service ("dry") tanks.

Not quite. The answer is Typically, one brake system operates the brakes on the front axle, and the other system operates the brakes on the rear axles.

A dual air brake system has two separate air brake systems, each with its own air tanks, hoses, lines, etc. Both systems are controlled by the one brake pedal. Typically, the primary system operates the brakes on the rear axle, and the secondary system operates the brakes on the front axle (and possibly one rear axle as well).

Not quite. The answer is glad hands

As part of your vehicle inspection test, if your vehicle is equipped with air brakes and has a trailer, you will inspect the air connections between the truck or tractor and the trailer. These connections are made with hose couplers (commonly called "glad hands" because they vaguely resemble shaking hands). These glad hands have rubber seals to form a tight connection and prevent air from escaping. Make sure that the glad hands are locked in place and free of damage or air leaks.

Not quite. The answer is a yellow lamp on the left side.

A converter dolly with antilock brakes is required to have a yellow ABS lamp on its left side. All converter dollies built since March 1, 1998 have antilock brakes.

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 let the air out of the brake chambers.

The parking brake control allows you to evacuate air from the brake chambers. With the air gone, the spring brakes will come on automatically and hold your vehicle in place.

Not quite. The answer is Never

Applying the spring brakes and the air brakes at the same time may put too much force on the brakes and can actually damage them.

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 1 inch

The slack adjusters won't move if the parking brakes are on. To check the slack adjusters, park on level ground, chock the wheels, and then release the parking brakes. Use gloves and pull hard on each slack adjuster that you can reach. If a slack adjuster moves more than about one inch where the pushrod attaches to it, it probably needs adjustment.

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 Ice may form in the air storage tanks and cause the brakes to fail.

Moisture in the warm, compressed air from the air compressor will condense as the air cools. In below-freezing temperatures, this moisture can freeze. Ice in the tanks and air lines can cause the brakes to stop working. Whenever the air compressor runs, the alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. (Alcohol has a lower freezing point than water.)

Not quite. The answer is the air pressure may drop too low during driving.

The manufacturer's specifications should state how fast the air pressure should build up once the engine has reached normal operating speed. If the air pressure does not build up fast enough during your final air brake check, the air pressure may not replenish quickly enough during normal braking either. Don't drive the vehicle until the cause has been found and corrected.

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

When you drive down long, steep downgrades, the braking effect of your engine is what's most important, and your service brakes are only a supplement to being in the proper low gear. They cannot compensate for your vehicle being in an unsafe high gear without putting too much pressure on your brakes.

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 Stop.

If the low air pressure warning comes on, there may be a leak in the system. Pull over and park your vehicle as soon as possible. If the air pressure drops too low, the spring brakes will come on automatically, which will stop your vehicle – but not necessarily in a safe way. Sudden application of the spring brakes while you're driving might result in a skid.

Not quite. The answer is More than 400 feet

The stopping distance equals the sum of the perception distance, reaction distance, brake lag distance, and braking distance. Under ideal conditions, the average driver of a bus or large truck equipped with air brakes and traveling at 55 mph would require about 451 feet to come to a complete stop. The length of a football field including the two end zones is 360 feet.

Not quite. The answer is a supply pressure gauge.

Every vehicle equipped with air brakes must have a supply pressure gauge that shows how much air pressure is available for braking.