Brake Terminology

ABS Speed Sensor: Sends electrical signal of wheel speed which the ABS computer compares to other readings to determine if wheels are losing traction.

ABS: Acronym for Anti-Lock Brakes.

Aftermarket: Part supplied by a company other than the original equipment or factory supplier.

Anchor End: Fixed pin mounted to the drum's backing plate that the shoes pivot on. Also a location where the return springs are attached.

Anti-Lock Brakes: By measuring wheel speeds, hydraulic brake fluid pressure is electronically controlled to prevent wheel lockup during heaving braking or low traction conditions.

Anti-Rattle Clips: Metal clips that hold brake pads and prevent them from vibrating.

Asbestos: A mineral fiber that is highly heat resistant, chemical and thermal stable with a high tensile strength. Used in friction materials and gaskets. Read more about Asbestos

ASE: Acronym for Automotive Service Excellence, an organization that tests and certifies automotive technicians.

Auxiliary Drum Parking Brake: Parking brake mounted inside the rear brake rotor on some models equipped with rear disc brakes.

Backing Plate: Steel plate that the wheel cylinder, shoes and other drum brake components are mounted on.

Bedding-In: Process of depositing an even layer of friction material onto the brake rotor or drum. Also known as Burnishing.

Bench Bleed: To prime the master cylinder with fluid to remove trapped air when not mounted to the vehicle.

Bleeder Screw: Hollow screw that allows air to be bled from a caliper or wheel cylinder.

Bleeding Sequence: Order of bleeding brakes depending on brake system type.

Bleeding: Procedure to remove air trapped in the brake system. Instructions for How To Bleed Brakes

Bonded Lining: Friction material attached to metal backing plate with adhesive as opposed to rivets.

Booster Vacuum Hose: Allows transfer of vacuum to brake booster for power brake function.

Brake Bias: The braking power proportion of the front brakes compared to the rear brakes. Same as Brake Ratio.

Brake Bleeding: Procedure to remove air trapped in the brake system. Instructions for How To Bleed Brakes

Brake Booster: Provides braking assist with vacuum or hydraulic pressure (hydroboost systems).

Brake Disc: Round metal or composite disc that provides a friction surface for brake pads. Also known as a Brake Rotor.

Brake Drag: Friction materials contacting rotor or drum after the brake pedal has been released.

Brake Drum Micrometer/Gauge: Precision tool that measures the inside diameter of the brake drum.

Brake Drum: Metal circular component that rotates with the wheel which the brake shoes contact.

Brake Fade: Reduction of braking power often caused by overheating the brakes.

Brake Fluid: Hydraulic fluid used to transmit master cylinder pressure to calipers or wheels cylinders. Read more info on brake fluid.

Brake Flush: Completely removing all existing brake fluid and replacing with new.

Brake Grab: An abrupt application of one brake compared to another.

Brake Hose: A flexible rubber or stainless steel hose that allows transmission of fluid through the braking system.

Brake Job: Inspecting all of the brake components, including replacing the brake linings, resurfacing or replacing the rotor and/or drums and bleeding the brakes.

Brake Light Switch: A mechanical or hydraulically activated electrical switch that turns the brake lights on and off.

Brake Line: Hard tubing that transfers fluid to various brake components.

Brake Lining: Another name for friction material.

Brake Machining: Process of turning a rotor or drum on a lathe to remove grooves and other surface imperfections.

Brake Master Cylinder: The component which creates hydraulic pressure and stores fluid in a reservoir.

Brake Modulation: Varying pedal pressure to keep the brakes on the verge of locking up.

Brake Pad Indicator: Metal tab mounted to brake pad to scrape against brake rotor at a predetermined depth.

Brake Pad Sensor: A electrical sensor mounted in a brake pad that grounds to the brake rotor at a predetermined depth to illuminate a dash light.

Brake Pad: Flat friction material either riveted or bonded to a metal backing plate. Usually made from organic, semi-metallic or ceramic materials.

Brake Pressure Switch: Hydraulically operated electrical switch used to turn brake lights on.

Brake Pull: Vehicle veers to left or right when brakes are applied.

Brake Ratio: The braking power proportion of the front brakes compared to the rear brakes. Same as Brake Bias.

Brake Reservoir: Container mounted to the brake master cylinder which stores brake fluid.

Brake Rotor Micrometer: Precision measurement tool used to determine the thickness of the brake rotor.

Brake Rotor: Round metal or composite disc that provides a friction surface for brake pads. Also called a Brake Disc.

Brake Shoe Heel: The brake shoe end opposite the toe.

Brake Shoe Toe: The end of a brake shoe that rests against the anchor pin. Also known as Anchor End.

Brake Shoe: Curved friction material either riveted or bonded to a metal backing plate forced against the inside of brake drum.

Brake Spring Pliers: Tool that removes and installs brake drum springs.

Brake Squeal: High pitched sound caused by metal to metal vibrations. More info see squeaking brakes.

Brake Vacuum Hose: Allows transfer of vacuum to brake booster for power brake function.

Brake Warning Light: Dash mounted light to indicate worn brake pads, pressure loss or other brake problem.

Braking Ratio: The braking power proportion of the front brakes compared to the rear brakes. Same as Brake Bias.

Burnishing: Process of depositing an even layer of the friction material onto the brake rotor or drum. Also known as Bedding-In.

Caliper Piston: Metal or composite cylinder that applies force to brake pads from hydraulic pressure.

Caliper Support: The metal bracket that attaches to the steering knuckle and holds the caliper. Also know as the Mounting Bracket.

Caliper: Converts hydraulic pressure to mechanical force that pushes the pads against the rotor. Calipers have at least one piston and two pads.

Certified Master Technician: An auto technician that has passed all eight ASE tests.

Certified Technician: An auto technician that has passed at least one of eight ASE tests.

Coefficient Of Friction: Ratio of force that maintains contact between two objects.

Cross-Drilled Rotor: Rotor with a series of holes drilled completely through the material to aid in cooling and braking performance.

Dash Warning Light: Dash mounted light to indicate worn brake pads, pressure loss or other brake problem.

Diagonal Brake System: A brake system with two separate hydraulic circuits connecting the wheels that are diagonally opposed.

Dial Indicator: Tool used to measure tiny movements such as disc runout.

Disc Brake Pad Spreader: Tool that pushes the piston back into the caliper before installing new brake pads. See Disc Brake Piston Tool for rear calipers with an integrated parking brake.

Disc Brake Piston Tool: Tool that rotates the piston back into the cylinder on rear calipers with an integrated parking brake.

Disc Brakes: Brake design that uses a caliper, rotor and pads.

Disc Runout: Thickness variation of brake rotor friction surface.

Disc Thickness Variation: Variation between two points on a rotor. Large variation can cause pulsating brakes.

DOT: Acronym for Department Of Transportation.

Dragging Brakes: Friction materials contacting rotor or drum after the brake pedal has been released.

Drum Brakes: Brake design that uses a wheel cylinder, drum and shoes.

Dual Circuit Brakes: A brake system with two separate hydraulic circuits connecting the wheels that are diagonally opposed.

Dual Master Cylinder: A master cylinder with two separate hydraulic circuits.

Duo-Servo: A self-energizing effect on the brakes due to servo action providing increased braking power.

Dust Cap: Metal cover that attaches to wheel hub to contain grease and keep contaminates out of wheel bearings.

Dust Shield: Metal cover that protects the disc brake components from splashing water and road debris.

EBCM: Acronym for Electronic Brake Control Module

Electronic Brake Control Module: Computer for ABS system.

Electronic Brake Force Distribution: Electronically controlled brake force balance between the front and rear brakes.

Emergency Brake: Rear brakes that operate independently of the front brakes and are actuated by a hand lever. Also called Hand Brake.

Equalizer: Divides the parking brake actuation between the left and right side.

Factory Replacement: Part that meets or exceeds the performance, durability and reliability of the original equipment or factory parts.

Fixed Caliper: A caliper design with opposing pistons and no sliding function.

Flare Wrench Set: A open-ended tool for brake fittings designed to fit around brake lines.

Fluid Contamination: Foreign matter mixed with brake fluid.

Flush: Completely removing all existing brake fluid and replacing with new.

Free Play: Distance the pedal moves before the master cylinder is actuated.

Friction Material: Replaceable material that generates friction between the rotor or drum.

Friction Surface: Surfaces used to contact each other to create friction.

Gas Fade: Brake fade cause by a gas layer between friction surfaces, causing loss of performance.

Glazed Brakes: Friction surface is glossy due to overheating. As a result, coefficient of friction drops, causing loss of performance.

Grinding Brakes: Metal backing plate or rivets from brake pad or shoe contacting rotor or drum. More info see Grinding Brakes.

Hand Brake: Rear brakes that operate independently of the front brakes, actuated by hand lever. Also known as emergency brakes.

Hard Pedal: Excessive pedal effort needed to stop vehicle.

Hard Spots: Area of the rotor or drum surface that is harder that surrounding areas. Can cause Pulsating Brakes.

Heat Dissipation: Process of removing heat.

Heat Spots: Dark areas or outlines on brake rotor caused by excessive heat. Can cause Hard Spots.

Hold-Down Spring: Spring that holds the brake shoe against the backing plate.

Hub: Component which houses the wheel bearing, and supports the wheel, brake rotor or drum.

Hydraulic Brake Hose: A flexible rubber or stainless steel hose that allows transmission of fluid through the braking system.

Hydraulic Brakes: A braking system that uses hydraulic pressure to function.

Hydro-boost: A braking system that uses hydraulic pressure provided by the power steering pump through a brake booster.

Hygroscopic: A characteristic to absorb water.

Judder: Pulsating movement of the brake pedal caused by uneven rotor or drum surface or out of round component.

Leading Shoe: The front shoe in a nonservo brake design.

Lining: The friction material attached to a metal backing on a brake pad or shoe.

Low Pedal: Brake system condition that requires excessive pedal travel to stop vehicle.

Manual Bleeding: A two person brake bleeding process performed by pumping the master cylinder.

Manual Brakes: Brake system that does not use power assist.

Master Cylinder: The component which creates hydraulic pressure and stores fluid in a reservoir.

Maximum Diameter: Largest inside diameter that a drum can be safely used.

Mechanical Fade: Heat expansion of the brake drum away from the shoes causing loss of performance.

Metering Valve: Valve that equalizes pressure between the front and rear brakes. Also know as a Proportioning Valve.

Minimum Thickness: The smallest thickness that a rotor can be safely used.

Modulation: Varying pedal pressure to keep the brakes on the verge of locking up.

Mounting Bracket: The metal bracket that attaches to the steering knuckle and holds the caliper. Also know as the Caliper Support.

Mushy Brakes: Soft brake pedal condition that requires excessive pedal travel to stop vehicle. Also called spongy brakes.

Non-Servo: Drum brake design in which the brake shoes operate independently of each other.

OE/OEM: Acronym for Original Equipment/Original Equipment Manufacturer.

Original Equipment: Part supplied by the original equipment manufacturer or factory supplier.

Pack Wheel Bearings: Process of forcing grease into wheel bearings.

Parking Brake: Rear brakes that operate independently of the front brakes that are actuated by a foot pedal.

Parking Brake Cable: Transfers the force from the parking brake pedal to the rear brakes.

Parking Brake Equalizer: Divides the parking brake actuation between the left and right side.

Pedal Feel: Sensation felt through the brake pedal by the driver during braking.

Pedal Free Play: Distance that the pedal moves before the braking action is started.

Pedal Height: Distance between the brake pedal and the floor of the vehicle.

Power Assist: A component added to the brake system that amplifies the braking action for reduced pedal effort.

Power Brakes: Brake system that uses power assist for reduced effort.

Pressure Bleeding: Brake bleeding process that uses air pressure to force fluid through the lines.

Proportioning Valve: Valve that equalizes pressure between the front and rear brakes. Also know as a Metering Valve.

Pulsating Brakes: Uneven force or vibration felt through the movement of the brake pedal caused by uneven rotor or drum surface or out of round component. Solutions for Pulsating Brakes

Reservoir: Container mounted to the brake master cylinder which stores brake fluid.

Resurfacing: Process of turning a rotor or drum on a lathe to remove grooves and other surface imperfections.

Retracting Spring: Springs that pull the brake shoes away from the drum.

Riveted Lining: Friction material attached to metal backing plate with rivets as opposed to using adhesive.

Rotor: Round metal or composite disc that provides a friction surface for brake pads.

Rotor Friendly: Used to describe brake pad type that does not aggressively wear brake rotor.

Runout: Thickness variation of brake rotor friction surface.

Scoring: Grooves worn into the brake rotor or drum.

Self Adjuster: Self-ratcheting mechanism that compensates for brake shoe wear.

Self-Energizing: An effect on the brakes due to servo action providing increased brake power.

Service Hole: Opening on backing plate or drum face allowing access to star adjuster or visual check of shoe thickness.

Shim: Thin metal plate providing insulation between brake pad, caliper and caliper piston.

Sliding Caliper: A two piece caliper design that pushes against one brake pad against the rotor and uses leverage to push the other.

Slotted Rotor: Rotor with a series of grooves cut in the surface of the material.

Solid Rotor: A rotor that is solid between each side of the friction surfaces.

Splash Shield: Metal cover that protects the disc brake components from water and road debris.

Spongy Brakes: Soft brake pedal condition that requires excessive pedal travel to stop vehicle. Also called mushy brakes. More info on Spongy Brakes

Star Wheel Adjusting Screw: Self-ratcheting mechanism that compensates for brake shoe wear.

Stopping Distance: Distance traveled between the initial application of the brakes and when the vehicle comes to rest.

Swept Area: Total surface area of the brake pad or shoe contacting the rotor or drum for one full revolution.

Torque Wrench: Tool for measuring force applied to a fastener

Trailing Shoe: The rear shoe in a nonservo brake design.

Turned: Process of turning a rotor or drum on a lathe to remove grooves and other surface imperfections.

Vacuum Booster: Provides power assist by using engine vacuum against a diaphragm to add mechanical force to the master cylinder.

Vented Rotor: A rotor that has cooling fins between each side of the friction surfaces to aid in cooling.

Water Fade: Brake fade cause by a water layer between friction surfaces, causing loss of performance.

Wear Indicator: Metal tab mounted to brake pad to scrape against brake rotor at a predetermined depth.

Wear Sensor: A mechanical or electrical sensor mounted to a brake pad that signal when the pads are worn to a predetermined level.

Wheel Cylinder: A component that uses hydraulic pressure to force opposing pistons apart which in turn pushes the brake shoes outward.

Wheel Cylinder Rebuild: Replacing rubber seals and cups and honing the cylinder.

Wheel Lockup: Condition when one or more wheels are not rotating when the vehicle is moving.

Wheel Sensor: Sends electrical signal of wheel speed which the ABS computer compares to other readings to determine if wheels are losing traction.

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