Brake Parts: Names and Components Explained

Most road vehicles use disc and/or drum brakes; the main parts are pads (linings), rotors (discs), calipers, brake hoses/lines, master cylinder, brake booster, proportioning/combination valve, ABS/ESC module and wheel-speed sensors, plus, where fitted, drums, shoes, wheel cylinders, and parking-brake cables or electric actuators. Below is a clear breakdown of what each component is called and where it fits in the system.

Core components in passenger-vehicle hydraulic brakes

Disc brake assemblies (common on front and many rear axles)

Disc brakes convert kinetic energy into heat by clamping pads onto a spinning rotor. The following list names the parts you’ll encounter on a typical disc-brake corner.

• Rotor (brake disc): solid or vented; sometimes drilled or slotted; “drum-in-hat” rotors include an internal parking-brake drum.
• Caliper: fixed or floating/sliding body that houses pistons and clamps pads.
• Caliper bracket (anchor bracket): mounts the caliper to the knuckle or axle.
• Caliper pistons: one or multiple; press pads against the rotor.
• Piston seals and dust boots: maintain hydraulic seal and keep debris out.
• Slide pins/guide pins with boots/bushings: allow floating calipers to move.
• Brake pads (linings/friction material): inner and outer pads, often with shims.
• Pad shims and anti-rattle/retainer clips: reduce noise and hold pads in place.
• Pad wear indicators: mechanical “squealers” or electronic wear sensors.
• Bleeder screw (bleed nipple): used to purge air from the caliper.
• Mounting hardware: caliper bolts, rotor set screws (where used).

Together, these parts deliver strong, consistent braking and are designed for quick service: pads are consumables; rotors and hardware are replaced as needed.

Drum brake assemblies (common on some rear axles)

Drum brakes press outward-facing shoes against a spinning drum. They package an integrated mechanical parking brake and are widely used on budget and light-duty rear axles.

• Brake drum: the rotating cast-iron shell the shoes press against.
• Brake shoes (primary/secondary): curved friction linings mounted to a shoe web.
• Wheel cylinder: hydraulic cylinder with two pistons that pushes the shoes outward.
• Return springs: pull shoes back after braking.
• Hold-down springs and pins: retain shoes on the backing plate.
• Adjuster (star-wheel) and lever/cable: maintains correct shoe-to-drum clearance.
• Anchor pin and shoe links: locate and connect the shoes.
• Backing plate: fixed plate that supports the drum hardware.
• Parking-brake lever/actuator: mechanical arm linking the cable to a shoe.
• Bleeder screw: used to bleed the wheel cylinder.

Drum hardware is spring-rich and typically serviced as a kit; shoes and drums are wear items, while cylinders and springs are replaced if leaking or fatigued.

Hydraulic supply and control (applies to disc and drum systems)

The hydraulic subsystem generates, multiplies, and meters braking force, while modern vehicles add electronic control for stability and anti-lock functions.

• Brake pedal and pushrod: driver input to the hydraulic system.
• Brake booster: vacuum booster (with check valve; may use an engine vacuum pump) or hydroboost (uses power-steering pressure).
• Master cylinder: converts pedal force to hydraulic pressure; includes reservoir, cap, and fluid-level sensor.
• Proportioning valve/combination valve: balances front/rear pressure; often includes a pressure-differential switch and, on older designs, a metering valve.
• ABS/ESC hydraulic control unit (HCU or modulator): solenoid valves and pump motor that modulate pressure for ABS, traction control, and stability control.
• Pressure sensors and switches: monitor line pressure for control modules and warnings.

These parts ensure the system delivers appropriate, controllable pressure to each wheel and enable safety features like ABS and stability control.

Brake lines, hoses, and fittings

Hydraulic fluid travels through rigid and flexible lines; correct routing and sealing are critical for safety and pedal feel.

• Hard lines (steel/copper-nickel): carry fluid along the chassis.
• Flexible brake hoses: connect moving suspension/brake components to hard lines.
• Banjo bolts with copper crush washers: seal hose-to-caliper connections.
• Unions, T-fittings, flare nuts: join and distribute hydraulic lines.
• Bleeder screws and caps: allow air removal and protect bleeder threads.
• Brake fluid: DOT 3, DOT 4, or DOT 5.1 glycol-based fluids (DOT 5 silicone is not compatible with ABS and many systems).

Regular inspection for corrosion, cracking, and leaks is essential; hoses and lines are safety-critical and replaced when compromised.

Parking brake systems

The parking brake holds the vehicle stationary mechanically, independent of hydraulic pressure; designs vary by platform and brake type.

• Cables: front, intermediate, and rear cables with an equalizer/adjuster.
• Hand lever or foot pedal: applies cable tension in manual systems.
• Drum-in-hat parking-brake shoes: small drum shoes inside a disc rotor hat.
• Caliper-integrated parking-brake mechanism: screw/ratchet inside the caliper.
• Electronic parking brake (EPB): caliper-mounted motors or a cable-pull motor, controlled by an EPB module and dash switch.

Whether cable-operated or electronic, the parking brake relies on dedicated hardware to secure the vehicle even if the hydraulic system fails.

ABS, traction, and stability control components

Modern vehicles integrate sensors and controllers to prevent wheel lockup and enhance directional control under braking and acceleration.

• Wheel-speed sensors (ABS sensors): magnetic or Hall-effect pickups at each wheel.
• Tone ring/reluctor (or encoded wheel bearing): provides the tooth pattern for sensing.
• ABS/ESC control module: processes sensor data and commands the HCU.
• Yaw rate, lateral acceleration, and steering-angle sensors: enable stability control.
• Brake pressure sensor and pedal-travel/booster sensors: refine system response.

These components work together to modulate brake pressure rapidly, helping maintain traction and vehicle stability in emergency or low-grip situations.

Wear items and service hardware

Beyond the major parts, several small components and consumables are routinely replaced during brake service to restore performance and suppress noise.

• Hardware kits: clips, springs, pins, and shims for disc and drum brakes.
• Guide-pin boots and bushings: maintain smooth caliper movement.
• Pad wear sensors: replaceable electronic leads or integrated pad sensors.
• Caliper rebuild parts: pistons, square-cut seals, dust boots.
• Hub/rotor screws, caliper bracket bolts (often torque-to-yield on some models).
• High-temperature brake lubricant: applied to pins and pad ears/shims (not a “part,” but standard in service).

Refreshing hardware during pad/rotor or shoe/drum replacement helps prevent uneven wear, vibration, and squeal.

Heavy-duty truck and bus air brake components

Commercial vehicles commonly use pneumatic (air) brakes, which rely on compressed air rather than hydraulic fluid.

• Air compressor and governor: generate and manage system air pressure.
• Air dryer and reservoirs: remove moisture and store compressed air.
• Treadle (foot) valve: driver’s brake input valve.
• Relay and quick-release valves: speed air delivery and release to chambers.
• Brake chambers: service chambers and spring (parking/emergency) brake chambers.
• Slack adjusters (manual or automatic) and S-cam or wedge mechanisms: convert chamber motion to shoe movement.
• Drums and linings (or air-disc rotors, calipers, and pads on newer systems).

Air-brake components are engineered for redundancy and serviceability, with automatic slack adjusters and air dryers critical for safe, consistent operation.

Bicycles and powersports (overview)

Two-wheel braking systems vary, but share many names with automotive components, particularly in hydraulic disc setups.

• Hydraulic disc: lever (master cylinder), hose, caliper, pistons, pads, rotor, bleed port.
• Mechanical disc: lever, cable, caliper (cable-actuated), pads, rotor.
• Rim brakes: calipers (dual-pivot, V-brake/cantilever), pads, cables/housing, levers.
• Motorcycles: rotors, calipers (often radial-mount), pads, master cylinder, ABS module and wheel-speed sensors on modern bikes.

While scaled differently, naming conventions for rotors, calipers, pads, and master cylinders largely align across bikes and motorcycles.

Common terms and synonyms

Brake parts often go by multiple names depending on region, manufacturer, or context. Here are frequent equivalents.

• Pads = linings; Shoes = linings (drum).
• Rotor = disc; Drum-in-hat rotor = integrated parking-brake drum.
• Caliper carrier = caliper bracket; Slide pins = guide pins.
• ABS sensor = wheel-speed sensor; Tone ring = reluctor.
• HCU = ABS modulator = hydraulic modulator; ESC module = stability control module.
• Vacuum booster = servo (UK); Master cylinder reservoir cap often contains a fluid-level switch.

Knowing alternate names helps when sourcing parts or reading service manuals across markets and brands.

Summary

Brake systems are assemblies of friction components (pads/shoes, rotors/drums), actuators (calipers, wheel cylinders), hydraulic or pneumatic supply and control (master cylinder, booster, valves, HCU), connections (lines, hoses, fittings), sensors (wheel-speed, yaw/steering for ESC), and parking mechanisms (cables, levers, EPB motors). Whether you’re identifying a noise source, ordering replacements, or planning maintenance, the names above cover the parts you’ll most commonly encounter across cars, trucks, buses, bikes, and motorcycles.

What are the six basic parts of a brake system?

The six basic parts of a hydraulic brake system are the Brake Pedal, Brake Booster, Master Cylinder, Brake Fluid, Brake Lines, and Wheel Brake Assemblies (which include calipers, pads, and rotors or drums, shoes). These components work together, using hydraulic pressure to convert the driver’s foot pressure on the pedal into frictional force that slows or stops the vehicle.
 
Here’s a breakdown of each part’s function:

1. Brake Pedal: The starting point of the system, it’s the pedal the driver presses to initiate braking. 
2. Brake Booster: This component uses vacuum to multiply the force applied by the driver’s foot on the brake pedal, making it easier to apply significant braking force. 
3. Master Cylinder: Often called the “heart” of the system, it converts the mechanical force from the pedal into hydraulic pressure. 
4. Brake Fluid: A hydraulic fluid stored in a reservoir, it transmits the pressurized force from the master cylinder to the wheel brakes. 
5. Brake Lines: These metal and rubber tubes carry the pressurized brake fluid from the master cylinder to the wheel brake assemblies. 
6. Wheel Brake Assemblies: This collective term includes:
   • Brake Calipers (for disc brakes): Clamps that hold the brake pads. 
   • Brake Pads (for disc brakes): Friction material that is squeezed against the rotor. 
   • Brake Rotors (for disc brakes): Metal discs attached to the wheel that slow down as the pads grip them. 
   • Brake Drums and Brake Shoes (for drum brakes): Found on some vehicles, where shoes press against the inside of a drum to create friction. 

What is the part called that holds the brake pads?

The part that holds the brake pads in a disc brake system is the brake caliper. The brake pads sit inside the caliper, and when you apply the brakes, the caliper clamps the pads against the spinning brake rotor to create friction and stop the vehicle.
 
How the caliper holds the pads:

• Caliper Body: The caliper is a clamp-like metal housing that surrounds the rotor. 
• Pistons: Hydraulic pistons inside the caliper move when you press the brake pedal, pushing the brake pads against the rotor. 
• Caliper Bracket: Some sources also mention the caliper bracket as the part of the assembly where the brake pads are installed. 
• Hardware: Anti-rattle clips or abutment clips also help to hold the brake pads in place and reduce noise. 

What are the 4 major parts of a disc brake system?

When it comes to disc braking systems, there are four parts you need to know: The pads, rotors, calipers, and hardware. The system is responsible for… well, braking. However, as with any other component within your vehicle, each aspect of the braking system serves a different purpose.

What are some brake parts called?

Here are the main parts of the brake system that you should know:

• -Brake Pad. This is a block-like structure that presses itself against the brake rotor to stop the wheels from rotating.
• -Brake Rotor.
• -Brake Caliper.
• -Brake Shoes.
• -Brake drum.
• -Backing Plate.
• -Return Springs.
• -Wheel cylinder.