What Is Spring Brakes?

Are you curious to know what is spring brakes? You have come to the right place as I am going to tell you everything about spring brakes in a very simple explanation. Without further discussion let’s begin to know what is spring brakes?

In the realm of automotive technology, safety features play a crucial role in protecting drivers, passengers, and other road users. One such safety feature that plays a critical role in commercial vehicles, such as trucks and buses, is the spring brake system. In this blog, we will delve into the concept of spring brakes, their functionality, and their significance in ensuring safe and reliable braking performance.

What Is Spring Brakes?

Spring brakes are a type of parking brake commonly found in heavy-duty vehicles equipped with air brake systems. Unlike traditional parking brakes, which are manually engaged by the driver, spring brakes are automatically activated when certain conditions are met, such as a loss of air pressure or disconnection of the air supply.

Functionality Of Spring Brakes

  1. Emergency Braking: The primary function of spring brakes is to provide emergency braking in the event of a loss of air pressure in the system. In air brake systems, compressed air is used to engage the brakes. If there is a significant air leak or a failure in the air supply, spring brakes automatically engage to bring the vehicle to a stop and prevent uncontrolled movement.
  2. Parking Brake: Spring brakes also serve as parking brakes when the vehicle is parked or stationary. When the driver sets the parking brake control, the spring brakes engage and hold the vehicle in place, preventing unintended rolling or movement.
  3. Fail-Safe Mechanism: Spring brakes act as a fail-safe mechanism in case of a failure in the air brake system. If there is a loss of air pressure due to a malfunction or an accident, the spring brakes ensure that the vehicle can still be brought to a controlled stop, providing an added layer of safety.

Components Of Spring Brake Systems

  1. Spring Brake Chamber: The spring brake chamber houses the powerful spring mechanism responsible for applying the brakes. When the spring brake is released, the spring is compressed, and the brakes are disengaged. In the event of a loss of air pressure, the compressed spring forcefully extends, applying the brakes.
  2. Service Brake Chamber: The service brake chamber, separate from the spring brake chamber, is responsible for the normal braking operation when the air brake system is functioning correctly. It receives air pressure from the brake system, which activates the brakes when the driver applies the brake pedal.
  3. Release Mechanism: Spring brakes have a release mechanism that allows the driver to disengage them manually when the air brake system is fully operational. This mechanism ensures that the spring brakes are only engaged when necessary, such as during an emergency or when the vehicle is parked.

Importance Of Spring Brakes

  1. Safety: Spring brakes are a vital safety feature, providing reliable braking performance even in emergency situations or when there is a failure in the air brake system. They help prevent accidents, uncontrolled vehicle movement, and enhance overall road safety.
  2. Compliance: In many jurisdictions, spring brakes are a mandatory requirement for commercial vehicles equipped with air brake systems. Compliance with these regulations ensures that vehicles meet safety standards and are equipped with necessary braking mechanisms.
  3. Driver Confidence: Spring brakes instill confidence in drivers, knowing that they have a reliable and effective braking system to rely on in critical situations. This confidence contributes to improved driver performance and decision-making on the road.


Spring brakes are an essential safety feature in heavy-duty vehicles equipped with air brake systems. Their functionality as emergency brakes and parking brakes ensures reliable stopping power and helps prevent accidents and uncontrolled vehicle movement. By understanding the significance of spring brakes, we can appreciate the role they play in enhancing safety and control, both for drivers and other road users.

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What Are Spring Brakes In Cdl?

Spring brakes are usually used to meet these needs. Powerful springs are held back by air pressure when driving. If the air pressure is removed, the springs put on the brakes. A parking brake control in the cab allows the driver to let the air out of the spring brakes.

What Is The Difference Between Spring Brakes And Parking Brakes?

In the service brake system the brakes are held retracted by springs, and applied by air pressure. Spring type parking brakes are applied and remain applied WITHOUT AIR PRESSURE. The parking brake chambers are attached to the service brake chambers and operate the brakes through the same linkage.

Do All Trucks Have Spring Brakes?

All trucks, truck tractors and buses must be equipped with emergency brakes and parking brakes. They must be held on by mechanical force (because air pressure can eventually leak away). Spring brakes are usually used to meet these needs.

Do All Semi Trailers Have Spring Brakes?

Newer trailers have spring brakes just like trucks and truck tractors. However, converter dollies and trailers built before 1975 are not required to have spring brakes. Those that do not have spring brakes have emergency brakes, which work from the air stored in the trailer air tank.


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