What is brake lag?
Answers
The time required for the brakes to work after the brake pedal is pushed
The distance between the brake pedal’s resting position and the floor
The amount of air pressure used to stop a vehicle
How faded the brakes are
The correct answer and explanation is:
The correct answer is: The time required for the brakes to work after the brake pedal is pushed.
Explanation:
Brake lag refers to the delay that occurs between pressing the brake pedal and when the brakes actually engage to slow or stop the vehicle. This phenomenon is most commonly associated with air brake systems, which are used in heavy vehicles like trucks, buses, and other large equipment. The delay happens because air brake systems rely on compressed air to activate the brakes, unlike hydraulic systems used in most passenger vehicles that work almost instantaneously.
In an air brake system, when the brake pedal is pressed, a signal is sent to the system to release compressed air from the reservoirs. This air travels through the lines to the brake chambers, where it pushes a diaphragm or piston to engage the brakes. The time it takes for the air to move through the system and apply the brakes is what is referred to as brake lag.
Brake lag is typically very short, often measured in fractions of a second (usually 0.2-0.4 seconds). However, this slight delay can be significant when traveling at high speeds or when a rapid stop is required. At highway speeds, even a small brake lag can translate into several feet of extra stopping distance.
This is why drivers of vehicles with air brakes must account for brake lag when calculating stopping distances. The total stopping distance for such vehicles is a combination of:
- Perception distance: The distance a vehicle travels while the driver recognizes the need to stop.
- Reaction distance: The distance traveled while the driver moves to press the brake pedal.
- Brake lag distance: The distance due to the delay in air brake application.
- Braking distance: The distance the vehicle travels once the brakes are applied.
Understanding brake lag is crucial for safe driving and proper operation of air-braked vehicles.