Compressed air in an air brake system usually contains a certain amount of water and compressor oil. The water and oil can damage the brakes if left to accumulate in the system. Tanks must be drained regularly to remove this build-up.

If your vehicle has air brakes, the air compressor drive belt should be checked before each drive. Check the tightness of the belt and verify that it is in good condition.

Drum brakes are attached to the wheels and located on the axles of a vehicle. The braking mechanisms that cause the vehicle to stop can be found inside of a drum brake.

In a vehicle with air brakes, the brake lights are activated when the brake pedal is pushed and air pressure moves an electric switch. With the application of air pressure, the switch will then turn on the brake lights.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A triple combination should have a leakage rate no higher than 6 psi in a minute during an applied leakage test.

Spring brakes do not work on all axles. If your vehicle's spring brakes activate due to low pressure in an air brake system, your vehicle will need a longer distance to stop than usual, especially if you are carrying a heavy load.

An air brake system has a safety relief valve, which releases air from the tanks if the pressure gets too high. If the valve must operate, something in the system is wrong and should be addressed by a mechanic.

The safety valve protects air tanks and the rest of an air brake system from accumulating too much air pressure. The safety valve is usually set to open at 150 psi.

Before beginning a trip, it is important to check the brake drums during your walk-around inspection. It is unsafe to drive if any brake drum has a crack more than one half of the width of the friction area.

A one-way check valve is required to be between an air compressor and the first main reservoir. This valve prevents air from escaping the system if the air compressor develops a leak.

When inspecting a vehicle with a dual air brake system, you should wait for air pressure to build from 85 to 100 psi in both the primary and secondary systems. This should take about 45 seconds.

If you have an Anti-Lock Braking System (ABS) equipped on only the tractor, only the trailer, or only one axle, you will still have more control over the vehicle when braking than you would without ABS. You should brake normally.

Vehicles with air brakes are required to be equipped with a low pressure warning device. A wig wag is a type of low air pressure warning device. This device drops a mechanical arm into the driver's view if the pressure in the tanks drops to a level between 55 and 75 psi.

Brakes are designed to take a lot of heat, but drivers should not rely solely on the brakes to slow their vehicle. Brakes may fade and lose their ability to slow down the vehicle if they become too hot, so drivers should also rely on the engine braking effect.

It is important to know the maximum air loss rate that is safe for your specific vehicle. A double combination vehicle should have a leakage rate no higher than 4 psi in a minute during an applied leakage test.

Both systems in a dual air brake systems share a single air compressor. If the air compressor is damaged, neither system will be able to operate properly.

In an air brake system, a low air pressure warning signal must come on if air pressure in the tanks falls below 60 psi. This warning signal may come in the form of a light, a buzzer, or a wig wag.

If you need to make an emergency stop, you can use either the controlled braking method or the stab braking method. It's important to brake in a way that keeps your vehicle in a straight line but will still allow you to turn if necessary.

A dual air brake system is made up of two separate air brake systems. The systems share a single set of brake controls, but each has its own air tanks, hoses, and lines. One system typically operates the regular brakes on the rear axle or axles while the other system operates the regular brakes on the front axle.

An alcohol evaporator can help prevent ice from building up in an air brake system. In cold weather, the evaporator should be checked and refilled every day.

On vehicles with Anti-Lock Braking Systems (ABS), yellow malfunction lamps alert the driver to ABS malfunction.

Never push down the brake pedal while the spring brakes are activated. The combined force of springs and air pressure could damage the brakes.

When performing a static leakage test on a double combination vehicle with air brakes, the leakage rate should be no more than 3 psi in one minute. If the air leaks from the air brake system at a quicker rate, the vehicle should not be driven because something likely needs to be repaired.

A dual air brake system is made up of two separate air brake systems. If there is an air leak in one system, it may not affect the other.

Compressed air usually contains a certain amount of moisture and compressor oil, which can build up in the air storage tanks and damage the brake system. The tanks should be drained to clean out these accumulations. On a tank with a manual drain valve, draining should be performed at the end of each day of driving.