Some pre-1975 vehicles have a front brake limiting valve, which has "normal" and "slippery" settings. The idea behind these valves was to limit the air pressure available to the front brakes when driving on slippery surfaces, and thereby reduce the danger of a front-wheel skid. Studies have found that this is not actually a concern, so if your vehicle has a front brake limiting valve, leave it in the "normal" position.

Always apply the parking brake when leaving your vehicle unattended.

When a brake pedal is pressed and the S-cam is turned, the S-cam presses the brake shoes against the inside of the brake drum. This causes friction and will cause the vehicle to slow.

Foundation brakes are used at each wheel. The most common type is the S-cam drum brake.

While driving downhill, you should hold down the brake pedal until your vehicle reaches a speed 5 mph below your safe speed, then release the brake pedal. Repeat this process.

Brakes are particularly prone to getting out of adjustment if they are hot. Be sure to routinely check the adjustment of your brakes. For a vehicle to be safely controlled, all brakes must be properly functioning and adjusted.

When driving a vehicle with air brakes, if the low air pressure warning light comes on, it is important for you to stop and safely park your vehicle as soon as possible. There may be a leak in the system. Controlled braking will remain possible only as long as there is enough air left in the tanks.

In an air brake system, there are three different braking systems: a service brake system, a parking brake system, and an emergency brake system. The emergency brake system uses parts of both the parking and service brake systems.

Because air pressure can eventually leak away, the emergency brakes in an air brake system must be held on by mechanical force.

As long as the brakes are properly maintained, using air brakes is a safe and effective method of stopping large, heavy vehicles.

Check each slack adjuster after parking on level ground, setting wheel chocks, and disengaging the parking brake. Pull the slack adjusters to make sure they do not move more than about one inch from where the push rod is attached. If they move more than one inch, they may be out of adjustment and will need to be fixed.

A wig wag is a type of low air pressure warning device in an air brake system. It drops a mechanical arm into the driver's view when the air pressure in the tanks falls below 60 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.

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.

Many large CMVs are equipped with air brakes. An air braking system uses compressed air to operate.

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.

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.

The most common type of foundation brake is an s-cam drum brake.

Some older vehicles have front brake limiting valves with "normal" and "slippery" settings. Setting a brake limiting valve to "slippery" reduces the vehicle's stopping power, so a driver should make sure the valve is in its "normal" position. Front wheel braking has proven to be effective in all driving conditions.

To prevent the build up of oil and water in a vehicle's air tanks, manually operated air tank drains should be used at the end of each day of driving.

It is essential that your low pressure warning light functions properly. After allowing the system to charge, you can test the warning signal by rapidly applying and releasing the brake pedal. This will release air from the braking system and the warning signal should come on when pressure drops to a dangerous level.

A modulating control valve allows a driver to gradually apply spring brakes. In equipped vehicles, the valve is controlled by a lever located on the dashboard.

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 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. Manually operated air tank drains must be opened daily to remove this build-up.

In a newer vehicle with air brakes, the parking brake is controlled by a diamond-shaped yellow knob. The knob is pulled out to apply the parking brakes and pushed in to release them.