Virginia CDL: Air Brakes Practice Test

Not quite. The answer is Otherwise, you will have to get a CDL with restrictions.

If you do not pass the air brake knowledge test, your CDL will include restriction L, which will limit you to driving vehicles without air brakes. So, good luck!

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 brake drum.

In North America, the most common type of foundation brake is the S-cam drum brake. The brake shoes and linings press against the inside of the brake drum, which causes friction to slow the wheel.

Not quite. The answer is parts of the service brakes and parking brakes

Spring brakes use powerful springs to apply the brakes. Normally, air pressure in the brake chambers holds back the springs. Should air pressure drop too low because of a leak, the springs will apply the brakes and stop the vehicle. To apply the parking brakes, you release air from the brake chambers manually.

Not quite. The answer is To prevent a buildup of ice in the air brake system

When the air compressor runs, an alcohol evaporator puts alcohol vapor into the air brake system to help prevent water in the lines or valves from freezing. Ice in the lines or valves can cause them to stop working.

Not quite. The answer is All of the above are true.

A dual air brake system is a system designed for safety and used on most heavy-duty vehicles. It uses one set of controls. Typically, the "primary" system operates the regular brakes on the rear axle, and the "secondary" system operates the regular brakes on the front axle.

Not quite. The answer is Tap on the brake drums.

If a brake lining has gotten frozen to the brake drum, you should be able to free it by using a hammer to tap on the drum near the brake lining. Be careful not to hit the brake lining because you might damage it. Note that you may also need to free the other brake lining in that drum brake. If the valves or other parts of the air braking system are frozen, you may be able to get them unstuck by putting commercial air brake antifreeze (NOT pure methyl alcohol) into the trailer air supply (red) line. However, this will not free frozen brake linings.

Not quite. The answer is compressed air

Air brakes use compressed air to make the brakes work.

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 Either the front or rear brakes will not be fully operational.

A dual air brake system has two separate air brake systems, each with its own air tanks, hoses, lines, etc. Typically, one system operates the brakes on the rear axle(s), and the other system operates the brakes on the front axle. If one of the systems loses air pressure, either the front or the rear brakes won't work properly. As a result, your vehicle's braking distance will increase. If this happens, stop your vehicle and get the system fixed. Continued braking would soon cause the spring brakes to come on.

Not quite. The answer is (b) or (c)

Before measuring pushrod stroke, chock the wheels of your vehicle. For an accurate measurement, make sure that tank air pressures are 90–100 psi. Here are two different methods for measuring pushrod stroke: (1) Make a mark on the pushrod where it exits the brake chamber, and see how far it moves from the brake chamber when the service brakes are applied. (2) Measure the length of the part of the pushrod from the brake chamber to the center of the clevis pin, and see how much it increases when the brakes are applied. To perform either method efficiently, two people may be needed: one to apply the service brakes, and one to make the appropriate measurements before and after the brakes are applied. There are also various pushrod stroke measuring tools available commercially that you can use.

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 a supply pressure gauge.

A supply pressure gauge is connected to a service tank (or possibly to both service tanks in a dual air brake system). It shows the amount of air pressure in the service tank.

Not quite. The answer is reduce air pressure at the front wheels.

Most modern tractors are equipped with an automatic front axle ratio valve, which supersedes the manual front brake limiting valve in older tractors. In light-to-moderate braking, the ratio valve automatically reduces air pressure (and hence braking force) to the front wheels to reduce the chance of front-wheel lockup (which could result in a skid) on slippery roads.

Not quite. The answer is 2 psi per minute.

Perform the first test of air leakage with the engine off and the brakes released. The air-loss rate should be less than 3 psi per minute for a combination vehicle and less than 2 psi per minute for a bus or straight truck. After you've tested this initial drop, now test air leakage with the engine off and the foot brake fully applied. This time, the air-loss rate should be less than 4 psi per minute for a combination vehicle and less than 3 psi per minute for a bus or straight truck.

Not quite. The answer is so you only have to apply the brakes just hard enough to feel a definite slowdown.

When starting down a downgrade, shift into a low gear and use engine braking to slow your vehicle. Apply the brakes just enough to keep your vehicle near your safe speed.

Not quite. The answer is 125 psi.

A typical air brake system will be fully charged at 125 psi. Check the manufacturer's specifications for the actual figure for your vehicle. The air compressor should stop pumping air at that point.

Not quite. The answer is It is shaped like the letter "S."

The S-cam really is S-shaped. As it rotates, it forces the brake shoes away from each other and toward the inside of the brake drum.

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 brake normally.

Antilock brakes will automatically keep your wheels from locking so you can brake normally.