18 Wheeler Brakes: A Look at Semi Truck Brake Systems

Semi-truck brake systems are complex systems with several separate stopping units. These include the service brakes, which apply pressure to the brake pedal through air or hydraulic pressure.

Semi-trucks have separate parking brakes, which must be used only during parking and are operated by heavy-duty springs. A third type of brake is the emergency braking system, which relies on a combination of parts from the service brake and parking brake systems. Heavy-duty trucks require tailored brake solutions to ensure efficient and safe operation. In addition, each braking system has its nuances.

Air brakes are self-explanatory. When attempting to stop, the braking system uses pressurized air to activate the braking mechanism, pushing pressurized air against the lining of the drum and disc when the driver steps on the brake pedal.

Since 1998, semi-trucks have also been equipped with anti-locking brake systems, which prevent the wheels from locking up and causing the driver to lose control of the vehicle.

Spring brakes are used as parking brakes—the reverse of air brakes. They are set when there is a lack of air pressure. The emergency brake system’s setup and use are a bit more complicated.

If the semi truck’s air brakes lose air pressure, the emergency brake system allows the spring brake to engage to stop the vehicle. In the event of total brake failure, a driver can manually apply the brakes. These sophisticated braking systems should offer a modicum of comfort to other drivers on the road.

Overview of Semi Truck Brakes

Semi truck brakes are critical to a semi truck’s safety and performance. They are designed to provide reliable and efficient braking power to help prevent accidents and ensure safe operation on the road. Unlike passenger vehicles, semi trucks typically use air-powered brakes, which rely on compressed air to activate the brake system. This contrasts with hydraulic brakes, which use brake fluid to transmit pressure to the brake pads. Compressed air in truck brakes ensures a more robust and fail-safe braking system, essential for the heavy loads that semi trucks carry.

Types of Brake Systems

There are several types of brake systems used in semi trucks, each with its unique mechanism and advantages:

• Air brake systems: The most common type of brake system in semi trucks is the air brake, which uses compressed air to activate the braking mechanism. This system is highly reliable and can handle the heavy-duty demands of semi-trucks.
• Hydraulic brake systems: These systems use hydraulic brake fluid to transmit pressure from the brake pedal to the brake pads. While more common in passenger vehicles, some semi-trucks also use hydraulic brakes.
• Disk brake systems: Disk brakes use a rotor and brake pads to power braking. They offer superior performance and heat dissipation, ideal for high-performance braking.
• Drum brake systems: Drum brakes use a drum and brake shoes to power braking. They are durable and provide consistent braking performance, especially in heavy-duty applications.

Components of the Brake System

The brake system of a semi-truck consists of several key components, each playing a crucial role in ensuring effective braking:

• Brake pedal: The pedal the driver presses to activate the brake system. It is the primary interface between the driver and the braking system.
• Brake pads: These pads contact the rotor or drum to power braking. They are essential for converting kinetic energy into heat, slowing down the vehicle.
• Brake drums: The drums that the brake shoes make contact with to provide braking power. They are commonly used in drum brake systems.
• Air compressor: This component compresses the air used to activate the brake system, ensuring a steady supply of compressed air.
• Air tanks: These tanks store the compressed air used to activate the brake system. T

LONGER STOPPING DISTANCE FOR SEMI-TRUCK BRAKES

However, it is no secret that big rigs take much longer to stop than the typical passenger car. A rule of thumb is that a tractor-trailer will take at least one-third longer to stop at highway speeds. High-performance brakes can significantly enhance the stopping capabilities of these vehicles, especially under heavy loads or towing conditions.

For this reason, it is always best to anticipate problems and drive safely when driving on the highway. We recommend that drivers who have a big truck closely behind them take steps to let the truck pass or move out ahead of it to avoid the potential for a sudden stop accident.

PROPER BRAKE MAINTENANCE REQUIRED

This all assumes that the semi-truck has broken the optimal and proper working conditions. Many of the truck accidents we investigate reveal that the trucking company, also known as a motor carrier, has not taken proper steps to ensure the trucks are safe for highway driving.

When a truck accident occurs because the brake system is not up to standards, the accident could have been prevented, or the seriousness could have been reduced substantially with proper operating brakes.

Maintaining brake pads and regularly checking for hydraulic fluid leaks are vital steps in ensuring the proper operation of a semi’s brakes. It is also important that the evidence is preserved and the scene evaluated as soon as possible after a big truck wreck. Trucking companies routinely try to put their trucks back in service as quickly as possible after a wreck to avoid an inspection by the injured person’s representatives.

Troubleshooting Common Issues with Semi Truck Brakes

Several common issues can occur with semi truck brakes, and understanding these can help in timely troubleshooting and maintenance:

• Air leaks: These can occur in the air compressor, air tanks, or brake chambers, leading to a loss of air pressure and reduced braking efficiency.
• Worn brake pads: Over time, brake pads can wear down, causing the brake system to malfunction. Regular inspection and replacement are crucial.
• Worn brake drums: Similar to brake pads, brake drums can also wear out, affecting the braking performance.
• Low air pressure: Insufficient air pressure can cause the brake system to malfunction. Therefore, ensuring the air tanks are properly pressurized is essential.
• Faulty brake pedal: A malfunctioning brake pedal can lead to inconsistent or ineffective braking. Regular checks and maintenance are required.

Related Resources:

Brakes- an integral part of semi trucks

How 18-Wheeler Air Brakes Work

Bad Brakes on Semi Trucks

Truck wrecks with bad brakes

About Greg Baumgartner

Greg Baumgartner is a preeminent rated personal injury lawyer based in Houston, Texas, with over three decades of experience representing severely injured clients in truck accidents. He founded Baumgartner Law Firm, in 1985, with a mission to provide excellent legal representation and personalized attention to every client.