Friction Materials Types and Terms

  • Asbestos materials used to be the most common type of friction materials, but due to connections to lung disease, they are being phased out of the market.
  • Brake bands use friction material to slow vehicles by pressing against the brake disc.
  • Brake lining is the heat-resistant material that creates friction in braking devices.
  • Ceramic friction materials are very popular because they eliminate squeal and audible vibrations. They are also less abrasive to rotors and their brake pads tend to have a longer life-span than those of other materials.
  • Clutch facings are used to maintain lower coefficients of friction, which provide smooth and stable clutch engagement/disengagement. They help reduce clutch chatter, are available in molded and woven compositions and can be found with asbestos or asbestos-free materials.
  • Disc brake pads squeeze the rotor to slow the disc.
  • Elastomeric materials are resilient and adaptable, and help maximize the consumption of power and energy. They were created especially for high speed and energy applications.
  • Fiberglass materials are new to the market, and are currently being tested for durability, preservation of rotors and drums and noise level.
  • Friction discs metal plates bonded with friction materials that are used to brake.
  • Graphitic materials are used in applications that have a higher temperature because of their good energy absorption. These kinds of materials help hold in heat for a long period of time.
  • Non-asbestos lining includes all friction materials made without asbestos, due to concern over the affect of asbestos on health. These tend to be more abrasive and accelerate rotor wear.
  • Paper materials have some of the best performance of the friction materials. They are made of fibers and fillers and, after the addition of water, are dried and compressed into a sheet.
  • Semi-metallic friction materials are high performance and designed to prevent fade and squeal. They handle heat better than many others.
  • Sintered metal materials are compacted friction modifiers and metallic powders, and work best with very little oil flow. They have the ability to operate in very high temperatures.

Balance - Refers to the stability between the front and rear brakes.
 
Bleeding - The process by which overheated or spoiled brake fluid and air bubbles are removed from the brake system.
 
Brake Drum - Metal housing bolted to an axle and vehicle wheel that looks like a large jar lid. Brake shoes are forced against the drum to stop rotating wheels.
 
Brake Lining - Heat-resistant friction material that presses against the disc/drum to create braking force.
 
Brake Pad - Made of friction materials and bonded to metal plates. Brake pads need to be replaced occasionally due to heavy wear.
 
Burnish - Process of wearing in brakes so that the contact between the friction material and the rotor or drum becomes stable.
 
Caliper - The assembly that houses the brake pad(s) and applies them to the rotor. This also houses the hydraulically operated pistons to which the pads are bonded.
 
Clutch - Any of various contraptions used to engage and disengage two moving parts of a shaft or shaft and driving mechanism. When changing gears, the clutch pedal is pressed, disengaging the clutch and allowing the gear change; when released, the clutch engages and transfers the rotating motion throughout the entire driveshaft.
 
Coefficient of Friction - The ratio of force necessary to move an object compared to the weight of the object itself.
 
Disc Brake - Consists of brake pads, caliper and rotor. This is the part of the brake system that actually stops the vehicle.
 
Drum - A large circular metal housing that looks like an oversized jar lid and is bolted to a vehicle's axle and wheel. Brake shoes are forced against the inner section of the drum, which then stops the rotating wheel.
 
Dynamometer - Apparatus in a laboratory used to test brake system performance.
 
Fade - Temporary reduced braking power. Fade results from overheating of the friction material.
 
Groove Patterns - Grooves on friction material that help dispel heat, get rid of fluid and eliminate noise.
 
Master Cylinder - The cylinder that contains hydraulic fluid and a piston. It is connected directly to the brake pedal and transmits pressure to the brake operating system.
 
Recovery - The return of braking performance to a normal level after fade has diminished. This measures friction materials' ability to perform after overheating.
 
Rotor - Also referred to as a disc or drum, this is the circular metal object to which the brake pads are applied, creating friction to slow and stop the vehicle.
 
Shoe - A steel semicircular form coated with a friction agent that presses against the inside of a drum when activated.
 
Squeal - High-pitched noise made when braking. Squeal indicates that brakes should be inspected for wear.