What Are the Brakes on a Truck Called?

On heavy-duty trucks, the primary braking system is called air brakes—formally, an air brake system. Within that system, drivers use service brakes (for normal slowing and stopping) and spring-applied parking/emergency brakes. Many trucks also employ auxiliary braking such as engine brakes (often called “Jake brakes”), exhaust brakes, or retarders. Light-duty pickup trucks typically use hydraulic brakes similar to passenger cars.

Why “Air Brakes” Are the Industry Standard

Most medium- and heavy-duty trucks rely on compressed air rather than hydraulic fluid to apply their brakes. Air is plentiful, easy to replenish via an onboard compressor, and safer in the event of leaks because the system is designed to default to a fail-safe spring-applied position if air pressure is lost. In everyday conversation, truck drivers and mechanics simply refer to them as “air brakes.”

The Main Types of Brakes Found on Trucks

The following list outlines the common categories of braking you’ll hear about on trucks, distinguishing between how the vehicle normally stops and the systems that assist during long descents or emergencies.

• Service brakes (air-operated): The foot-pedal brakes used for routine slowing and stopping; on heavy trucks these actuate drum or air disc brakes via compressed air.
• Parking/emergency brakes (spring brakes): Powerful mechanical springs hold the brakes on when air pressure is released; used for parking and as a fail-safe if air is lost.
• Auxiliary brakes (engine/exhaust brakes, retarders): Non-friction systems that slow the drivetrain—e.g., compression-release “Jake brakes,” exhaust backpressure brakes, or hydraulic/electric retarders.
• Hydraulic service brakes (light-duty trucks): Pickups and some medium-duty chassis may use hydraulic disc/drum systems like passenger cars.
• Regenerative braking (electric trucks): Electric motors recapture energy while slowing; these are integrated with pneumatic service brakes for full stopping power.

Together, these systems share the work of controlling vehicle speed, reducing wear on friction components and improving safety—especially on long grades and with heavy loads.

How an Air Brake System Works

An air brake system stores compressed air in reservoirs and uses valves to meter that air to wheel brakes when the driver presses the pedal. Electronic controls such as ABS and stability systems modulate pressure to prevent lockup and improve control.

Core Components You’ll Hear Mentioned

Below is a breakdown of the essential parts that make up a modern heavy-truck air brake system and what each one does in service.

• Air compressor and governor: Generates compressed air and regulates system pressure.
• Air dryer and filters: Remove moisture and contaminants to prevent corrosion and freezing.
• Reservoirs (primary/secondary): Store pressurized air for redundancy and capacity.
• Foot (service) brake valve: Driver’s pedal that meters air to the brakes.
• Relay and quick-release valves: Speed up application and release of brakes, especially on long rigs.
• Brake actuators (chambers): Convert air pressure to mechanical force; spring-brake chambers also provide parking/emergency function.
• Foundation brakes: S-cam drum brakes or air disc brakes mounted at the wheels.
• ABS/EBS modules and sensors: Prevent wheel lockup and enable electronic control; EBS integrates electronic actuation common in newer European systems.
• Trailer brake controls: Service and emergency lines plus a hand valve or in-cab controller to manage trailer braking.

These components work together so that pressing the pedal translates into controlled, reliable braking force, with redundancy to keep the vehicle safe if a line or component fails.

Common Configurations: Drum vs. Air Disc Brakes

Truck “foundation brakes” at the wheels come in two main designs. The choice affects stopping distance, fade resistance, maintenance, and weight.

• S-cam drum brakes: The long-time standard; durable and widely supported, but can be more prone to fade and require periodic adjustment (automatic slack adjusters are now common).
• Air disc brakes (ADB): Increasingly common on new tractors and trailers, offering shorter stopping distances, better fade resistance, and easier pad service—often at a higher initial cost.

Fleets increasingly spec air disc brakes on steer and drive axles, especially where performance and uptime justify the investment.

What Drivers Call Them

Colloquial terms matter in the cab and shop. Here’s how drivers and techs often refer to the major braking functions.

• “Air brakes”: The whole pneumatic service braking system.
• “Spring brakes” or “parking brake”: The dash-controlled, spring-applied parking/emergency brakes.
• “Jake brake”: A brand-name shorthand for a compression-release engine brake; opens exhaust valves near top dead center to turn the engine into an air compressor.
• “Trolley valve” or “hand valve”: A control to apply trailer service brakes independently (usage varies and may be restricted by policy/regulation).

These terms help distinguish between using friction brakes with the pedal and using auxiliary systems to manage speed and heat on grades.

Safety, Standards, and Emerging Tech

Air brake performance is governed by strict regulations and is evolving with electronics and electrification.

• Regulations: In the U.S., FMVSS 121 sets stopping and performance standards; ABS is mandatory on heavy vehicles. Europe follows UNECE rules such as R13 and R131 for braking and advanced emergency braking.
• Electronic controls: ABS and electronic stability control are widely deployed; electronic braking systems (EBS) are common in Europe and appearing in more North American specs.
• Automatic emergency braking (AEB): The U.S. has proposed rules to require AEB on heavy vehicles; the EU has phased requirements for AEBS on many truck categories.
• Electric trucks: Regenerative braking reduces load on air brakes but does not replace them; integrated control blends regen with pneumatic braking for consistent pedal feel.
• Noise and local rules: Many municipalities restrict loud engine-brake use (“No Jake Brake” signs) where muffling is inadequate.

The net effect is that modern truck braking blends robust mechanical design with electronics to shorten stopping distances, improve control, and cut maintenance costs.

Maintenance and Best Practices

Properly maintained brakes are critical for safety and compliance. The checks below are common elements of pre-trip and service routines.

• Air system health: Drain tanks (if not automatic) to remove moisture; verify air dryer service; check governor cut-in/cut-out pressures.
• Leak checks: Perform applied and static air-leak tests; address audible leaks immediately.
• Stroke and adjustment: Confirm proper pushrod stroke; ensure automatic slack adjusters are functioning.
• Lining/pad and drum/rotor condition: Inspect for wear, cracks, heat checking, or glazing.
• ABS/EBS faults: Resolve dash warnings; verify wheel-speed sensor integrity.
• Trailer connections: Inspect gladhand seals, lines, and couplers; confirm emergency line integrity.

Consistent inspections, along with timely replacement of wear items, keep stopping performance within spec and prevent costly roadside out-of-service citations.

Bottom Line

When people ask what the brakes on a truck are called, they’re usually referring to air brakes—the compressed-air service and parking systems that stop heavy vehicles. Around that core, auxiliary systems like engine brakes and retarders share the workload, while newer disc brakes, electronics, and regenerative braking continue to push performance and safety forward.

Summary

Heavy-duty trucks use air brakes—comprising service brakes for normal stopping and spring-applied parking/emergency brakes—as their primary stopping systems. Drivers also rely on auxiliary braking (engine/exhaust brakes and retarders) to manage heat and speed, especially on grades. Light-duty trucks often use hydraulic brakes. Modern fleets are adopting air disc brakes and electronic controls such as ABS, stability control, and, increasingly, advanced emergency braking, while electric trucks integrate regenerative braking with traditional pneumatic systems.

What are the brakes on a truck?

Truck brakes are heavy-duty versions of what you see in cars, but built to handle 10x more weight and stress. A typical truck braking system combines mechanical parts (like discs and drums) with air pressure, hydraulic fluid, or even computers to slow down massive vehicles.

What are rear brakes called?

Rear brakes are called drum brakes or disc brakes, depending on the vehicle’s design. While both disc brakes and drum brakes are types of brakes, drum brakes are commonly used on the rear wheels of modern cars because they are cost-effective and the front wheels provide most of the vehicle’s stopping power. 
How drum brakes work:

• A brake drum rotates with the wheel. 
• The brake drum has an internal surface that the brake shoes press against. 
• When the brake pedal is pressed, hydraulic fluid pushes pistons in the wheel cylinder. 
• The pistons then force the brake shoes outward against the spinning drum, creating friction to slow the vehicle down. 

Why drum brakes are often on the rear:

• Cost-effectiveness: Drum brakes are generally cheaper to manufacture than disc brakes. 
• Reduced stopping power needed: Since the front wheels provide most of the stopping power, drum brakes are sufficient for rear-wheel braking duty. 
• Parking brake integration: Many vehicles use a “drum-in-hat” system, which integrates the parking brake within the disc brake rotor. 

When to use disc brakes on the rear:

• Modern, high-performance vehicles often feature disc brakes on all four wheels. 
• These brakes can provide better cooling and quicker stopping power compared to drum brakes. 

How many types of brakes are in a truck?

3 different braking
Air brakes are a good and safe way of stopping large and heavy vehicles, but the brakes must be well maintained and used properly. Air brakes are really 3 different braking systems: service brake, parking brake, and emergency brake.

What are brake pads vs brakes?

“Brakes” refer to the entire system used to slow or stop a vehicle, while “brake pads” are a specific, wearable component within that system that creates friction against a rotating rotor to convert kinetic energy into heat. Think of it like this: the brakes are the whole orchestra, and the brake pads are the violins playing their part to make the music (i.e., stop the car).
 
Brakes (The System)

• Definition: A broad term for the complete mechanism that slows or stops a vehicle by absorbing its kinetic energy. 
• Components: Includes parts like the brake pedal, master cylinder, hydraulic lines, calipers, rotors, and brake pads (or brake shoes in older systems). 
• Function: To generate friction and convert the vehicle’s motion into heat, thereby slowing it down. 

Brake Pads (The Component)

• Definition: The friction material that is pressed against a rotating disc (the rotor) as part of a disc brake system. 
• Material: Typically made of a friction material (like organic compounds, semi-metallic, or ceramic) bonded to a steel backing plate. 
• Function: To create the necessary friction against the brake rotor to slow or stop the wheel’s rotation. 
• Wear and Replacement: Brake pads are designed to wear down over time and are a consumable part of the braking system that needs regular replacement. Worn-out pads become less effective, and letting them go too long can damage more expensive components, such as the rotors.