How Semi-Truck Brakes Work

How Semi-Truck Brakes Work

Semi-truck brakes work differently from other vehicles; learn more here!

Semi-truck brakes are a fundamental mechanism in a commercial truck. Unlike sedan or small van brakes, semi-truck brakes are responsible for stopping over thousands of pounds of extra weight if they carry a full load. This means that they need an incredibly powerful, reliable braking system to ensure everyone’s safety on the road. So how exactly do they work? 

How Do Semi-Truck Brakes Work? 

Ultimately, semi-truck brakes work similarly to a personal car or pick-up truck, except compressed air is used instead of hydraulic brake fluid. Since hydraulic brake fluid has the potential to leak, leading to a malfunction, air is considered more reliable for large vehicles. Generally, semi-truck brakes are powered by compressed air, which is made by a compressor mounted on the engine and stored in tanks until it’s needed. There are a couple of types of semi-truck brakes, including disk and drum brakes, which work a little differently. Both systems start when the brake pedal is pressed, and the air from the storage tanks is released via brake valves into the brake chambers. 

How Do Disk Brakes Work? 

Disk Brakes work by using a caliper, brake pads, and a rotor to apply enough force to stop the semi-truck. The mechanism works by the caliper transferring force to an inner brake pad. Then, the caliper slides on guide pins as the brake pad makes contact with the rotor, and a bridge moves with the caliper to an outer brake pad on the rotor. When those brake pads squeeze against the rotor, the force transfers to the wheel, and it stops rotating. Once the trucker releases the brake pedal, the caliper returns to its original position. 

How Do Drum Brakes Work? 

Drum Brakes utilize slack adjusters, a pushrod, a cam, shoes, and a drum to generate enough pressure to stop the truck. This works by the compressed air moving the pushrod to put pressure on the slack adjusters, which transfer the stopping force into the cam. The cam starts to rotate, and the rollers rise up and put pressure on the shoes, so they push against the drum, causing the wheels to stop rolling. Once the driver releases the brake pedal, all parts move back into place, and the semi-truck brakes are released. 

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