Rhode Island CDL: Air Brakes Practice Test

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 They are not as strong as service brakes.

Spring brakes start to drag as pressure drops to about 60 psi, and they release as pressure rises to about 60 psi. Yet a full service brake application can be 100 psi. The coil spring in most spring parking brake chambers can exert a force of between 1,500 and 2,000 pounds. With a full service brake application of 100 psi, a typical Type 30 brake chamber can produce a force of 30 × 100 = 3,000 pounds.

Not quite. The answer is It supplies compressed air from the service tank with the highest pressure.

A two-way check valve allows compressed air from two different sources to flow through the same air line. The valve will select the source with the higher pressure. In this case, a two-way check valve is connected to both the primary and secondary service tanks to always draw air from the tank with the higher pressure and send it to the parking brake control valve. This arrangement ensures that the higher pressure is available to release the spring parking brakes. It also ensures that the spring parking brakes will not activate if pressure is lost in just one of the two tanks.

Not quite. The answer is 45

In dual air systems with minimum-sized air tanks, the pressure should build from 85 to 100 psi within 45 seconds. (With larger air tanks, it can take longer. Check the manufacturer's specifications for the expected amount of time.) If it takes longer than it should, there may be a problem with your system that may cause you to lose air pressure while you're driving.

Not quite. The answer is 55 to 60 psi.

A low pressure warning signal visible to the driver must come on before the pressure in the service air tank falls below 55 psi (or one-half the air compressor governor cutout air pressure on older vehicles).

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 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 Rhode Island Commercial Driver License Manual to familiarize yourself with what each one does.

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 you will still have enough air in the storage tanks to apply the air brakes several times.

The air storage tanks hold enough air for you to apply the air brakes several times.

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 Use gloves and pull hard on each slack adjuster you can reach.

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

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 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 The dashboard air pressure gauges won't drop when it's drained.

It may be difficult to visually identify the supply tank. Instead, remember that your dashboard air pressure gauges monitor the air pressure in the primary and secondary service tanks. (In some vehicles, there are two gauges, one for each service tank; in other vehicles, there is one gauge with two needles.) Draining the service tanks will cause the gauges to show a drop in air pressure in those tanks. The supply tank is the tank that does NOT drop the gauges when it's drained.

Not quite. The answer is air pressure.

Spring brakes contain powerful springs that are normally held back by air pressure. If the pressure drops too low, the spring brakes will automatically kick in.

Not quite. The answer is Safety valve

Drum brakes are on each of your vehicle's axles and contain about 10 different parts, including the axle, slack adjuster, and brake drum itself. While a safety valve is part of the air brake system, it is not part of the drum brake.

Not quite. The answer is Leaky glad hand seals

Glad hands have rubber or urethane seals to form a tight connection and prevent air from escaping. The glad hands are constantly being connected and disconnected, so the seals tend to wear out over time. Leaky seals can cause loss of air pressure.

Not quite. The answer is Apply the brakes as hard as you can without locking the wheels.

In controlled braking, you apply the brakes as hard as you can without locking the wheels. Keep steering wheel movements very small while doing this. This method of emergency braking does not require you to lock the wheels. Hence it is compatible with antilock brakes (ABS).

Not quite. The answer is when air is pumped into the air storage tanks.

The air compressor runs at all times while the engine is running. To keep the air pressure from eventually rising too high, the air compressor governor controls when the compressed air from the air compressor should flow into the air reservoirs. When air pressure drops to a certain level (typically 100 psi), the governor "cuts in" and routes the compressed air into the storage tanks. When air pressure rises to a certain level (typically 125 psi), the governor "cuts out" and routes the compressed air out of the system, into the atmosphere.

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.