The truck brake system plays a vital role in ensuring safety and efficient operation on all roads. Understanding the braking system is essential knowledge that helps drivers proactively control the vehicle, minimize accident risks, and extend the vehicle’s lifespan. This article from Xe Tải Mỹ Đình experts will provide detailed and comprehensive information about “truck brakes,” going beyond the original article, optimizing SEO, and providing real value to readers.
What is a Truck Brake System?
A truck brake system is a complex mechanical assembly designed to generate friction, thereby controlling and reducing the rotational speed of the wheels. The main goal of the brake system is to help the vehicle slow down or stop safely and effectively according to the driver’s commands.
The truck brake system performs the following important functions:
- Reduce vehicle speed: When the driver applies pressure to the brake pedal, this force is transmitted to the brake assembly, creating friction between the brake components and the wheels. This friction slows down the wheel’s rotation, helping the vehicle decelerate.
- Stop the vehicle completely: When braking hard, the large braking force generates enough friction to stop the wheels from rotating completely, helping the vehicle stop quickly and safely in emergency situations or at the desired stopping point.
- Hold the vehicle stationary: The parking brake (handbrake) is an important part of the brake system, with the function of keeping the vehicle stationary when parked, especially on slopes or uneven terrain, preventing the vehicle from drifting or moving unintentionally.
Drum brakes and disc brakes: Two types of common brake assemblies on trucks today.
Detailed Structure of a Truck Brake System
The truck brake system consists of three main components that work together harmoniously to ensure optimal braking performance:
1. Brake Assembly
The brake assembly is the part that directly creates friction with the wheels, determining the vehicle’s ability to decelerate and stop. There are two common types of brake assemblies on trucks:
a. Drum Brake
The drum brake is a traditional type of brake, consisting of:
- Brake Shoes: Two arc-shaped brake shoes that are pressed against the brake drum to create friction.
- Brake Linings: Friction material attached to the brake shoes, directly contacting the brake drum.
- Brake Drum: A hollow cylindrical part, attached to the wheel and rotating with the wheel.
- Wheel Cylinder: Uses hydraulic or pneumatic pressure to push the brake shoes against the brake drum.
- Return Springs: Pull the brake shoes back to their original position when the brake is released.
b. Disc Brake
Disc brakes are modern and more efficient, consisting of:
- Brake Rotor/Disc: A round metal disc, attached to the wheel and rotating with the wheel.
- Brake Pads: Two brake pads clamp tightly on the brake disc to create friction.
- Brake Caliper: Contains the piston and brake pads, with the function of pressing the brake pads against the brake disc.
- Brake Piston: Pushed by brake fluid pressure, creating force to press on the brake pads.
- Return Springs or Caliper Piston Seal: Help the brake pads separate from the brake disc when the brake is released.
In addition, the brake assembly also has auxiliary parts such as:
- Brake Backing Plate: A support for the parts of the drum brake.
- Brake Adjuster: An automatic or manually adjustable mechanism that maintains the proper clearance between the brake pads and the drum/disc brake.
- Anti-rattle Clips/Shims: Reduce noise and vibration when braking.
2. Brake Linkage/Actuation
The brake linkage transfers force from the driver’s brake pedal to the brake assembly. Trucks typically use two main power transmission systems:
a. Hydraulic Brake System
- Uses brake fluid to transmit force.
- When the brake is applied, the piston in the master cylinder creates pressure in the brake fluid.
- This pressure is transmitted through the oil lines to the wheel cylinders at each wheel, activating the brakes.
- Advantages: Fast response, even braking force.
- Disadvantages: Easy to lose pressure if the oil leaks.
b. Air Brake System
- Uses compressed air to transmit force, common on heavy trucks and tractor-trailers.
- The pneumatic system includes an air compressor, air tank, control valve and air lines.
- When the brake is applied, the control valve opens the compressed air path to the brake assembly, creating braking force.
- Advantages: Large braking force, safe when there is a leak (the brake will automatically lock).
- Disadvantages: Slower response than hydraulic, more complex system.
3. Brake Actuation Unit
The brake actuation unit controls the braking force as desired by the driver. There are two main types:
a. Mechanical Linkage
- Uses a system of levers, cables or connecting rods to transmit force from the brake pedal to the master cylinder or pneumatic valve.
- Simple, low cost but limited power transmission efficiency, often combined with brake assist.
b. Electronic Brake System – EBS
- Uses sensors and electronic controllers to optimize braking force on each wheel.
- Combined with active safety systems such as ABS (anti-lock braking system), ESC (electronic stability control), to enhance braking efficiency and vehicle stability.
- Modern, highly effective but more complex and costly.
Operating Principle of a Truck Brake System
The truck brake system operates on the principle of converting kinetic energy into heat energy through friction. The operating process is as follows:
- Actuate the brake pedal: The driver depresses the brake pedal, creating force on the system.
- Transmit force to the Brake Booster (optional): The brake booster (usually using vacuum or atmospheric pressure) amplifies the braking force, helping the driver reduce the required effort.
- Master cylinder creates pressure: The force from the pedal (or through the booster) acts on the piston in the master cylinder, creating brake fluid pressure (in hydraulic systems) or activating the pneumatic valve (in pneumatic systems).
- Transmit pressure to the wheel cylinder/brake assembly: Pressure is transmitted through pipes to the wheel cylinder (drum brakes) or directly to the piston in the brake caliper (disc brakes).
- Create friction and reduce speed: The pressure pushes the piston to press the brake pads against the brake drum (drum brakes) or brake disc (disc brakes), creating a large amount of friction. This friction reduces the rotational speed of the wheels, causing the vehicle to decelerate or stop.
- Release the brakes: When the driver releases the brake pedal, the pressure decreases, the return spring pulls the brake shoes/brake pads back to their original position, releasing friction and allowing the wheels to rotate freely again.
Diagram illustrating the operating principle of a truck brake system.
How to Adjust Truck Brakes (Brake Adjustment)
“Adjusting brakes” or brake adjustment is a necessary operation to maintain the optimal clearance between the brake pads and the drum/disc brake. If this clearance is too large, it reduces braking efficiency; if it is too small, it causes brake lock and rapid brake pad wear.
Steps to adjust drum brakes (for reference):
- Park the vehicle on a flat surface, turn off the engine, and apply the parking brake.
- Block the wheels to ensure safety.
- Loosen the locking screw of the brake adjustment mechanism.
- Turn the adjustment screw:
- Turn clockwise: increase clearance (less brake engagement).
- Turn counterclockwise: decrease clearance (more brake engagement).
- Adjust until the wheel rotates freely but the brakes engage when the pedal is pressed moderately.
- Tighten the locking screw.
- Check by test driving the vehicle.
Note: The brake adjustment procedure may vary depending on the vehicle type and brake system. Consult the manufacturer’s instructions or go to a reputable garage for assistance.
Common Issues and Warning Signs of a Truck Brake System
A faulty brake system is a dangerous situation that can lead to serious accidents. Early recognition of warning signs and common faults helps owners and drivers proactively maintain and repair them in a timely manner.
Warning Signs of Brake Failure:
- Unusual brake pedal: Hard, soft, sinks deeply or has more free play than usual.
- Reduced braking efficiency: Brakes do not engage, do not engage evenly between wheels, longer braking distance.
- Vehicle veers when braking: The vehicle tends to pull to one side when the brake is applied.
- Strange noises from the brake system: Squealing, screeching, rattling when braking or not braking.
- Burning smell when braking: Due to overheated or burnt brake pads.
- Brake warning light on the dashboard comes on.
- Vibration when braking: Due to warped or uneven brake disc.
Common Issues:
- Worn brake pads: The most common fault, brake pads wear down over time, reducing braking efficiency.
- Worn, warped, cracked drums/discs: Reduces contact area, causes vibration and reduces braking efficiency.
- Brake fluid/air leakage: Causes loss of pressure, leading to weak brakes or complete brake failure.
- Faulty brake cylinder: Cylinder is stuck, leaking, not creating enough braking pressure.
- Faulty brake pressure regulating valve: Causes imbalance of braking force between the wheels.
- Faulty brake booster: Makes braking heavy, reduces braking efficiency.
- Brake lock: Brake pads do not fully release after the brake is released, causing the brake pads to overheat, wear quickly, and increase fuel consumption.
Truck brake lock: A sign that the brake pads are not releasing, which is dangerous during operation.
Proper Truck Brake System Maintenance
Regular and proper maintenance is the key to a stable, safe, and long-lasting brake system. Important maintenance items:
- Check and replenish brake fluid: Periodically check the brake fluid level, ensuring it is always at the “MAX” level. Change the brake fluid as recommended by the manufacturer (usually every 2-3 years or 40,000-60,000 km).
- Check and replace brake pads: Check the brake pad thickness periodically. Replace when brake pads are worn to the permitted limit or show signs of damage.
- Check and maintain drums/discs: Check the surface of the drums/discs, if worn, warped, cracked or with deep grooves, they must be machined or replaced.
- Check brake cylinders and oil/air lines: Check for leaks, ensure cylinders operate smoothly, and lines are not cracked or dented.
- Check and maintain other parts: Pressure regulating valve, brake booster, return springs, brake adjustment mechanism…
- Install brake pad wear sensors (optional): Sensors help to warn early when the brake pads are worn to the point of needing replacement.
U-TRUCK brake wear sensor: A solution to improve safety and convenience.
Important Notes When Maintaining Truck Brakes
- Choose a reputable garage: Brake maintenance is an important job that needs to be performed at professional garages, with skilled technicians and modern equipment.
- Follow the maintenance procedure: Perform maintenance according to the correct procedure and recommendations of the vehicle manufacturer.
- Use genuine parts: Ensure the quality and durability of the brake system by using genuine replacement parts or from reputable suppliers.
- Periodic checks: Perform periodic brake system checks, even if there are no unusual signs, to detect potential problems early.
U-TRUCK is proud to be a leading distributor of genuine truck brake system parts in Vietnam. We are committed to providing high-quality parts, competitive prices and the best after-sales service.
In summary, mastering the knowledge of the truck brake system is a key factor to ensure safe and efficient operation. To buy genuine truck parts, please visit the website https://u-truck.vn/ or contact Hotline 081 680 8899 for dedicated advice.
