Brake Pads: Ceramic Vs. Compositeby Kevin Ann Reinhart
For many motorists, ceramic brake pads are an upgrade to the older, semi-metallic composite pads or non-asbestos organic friction materials. Heavier vehicles, such as trucks or large sports utility vehicles, should stay with using semi-metallic linings as higher loads and braking temperatures cannot be adequately handled by the ceramics. Cars originally fitted with ceramic pads or non-asbestos organic linings may be safely retro-fitted with ceramic brake pads.
Composite Brake Pads
Composite brake pads contain steel wool or fibers that provide strength and carry heat away from the brake rotors. The downside to composites is they tend to be noisy and abrasive, causing greater wear to the rotors. As composites wear, they produce visible brake dust that sticks to the alloy wheels which then need cleaning more often as the dust accumulates.
Ceramic Brake Pads
Ceramic brake pads first appeared in the early 1990s. Copper fibers replaced steel in ceramic composites, producing a brake pad that reduced friction on the pads and rotors, eliminating the squeal of steel-based composites. As ceramic pads wear, they produce a lighter, less visible dust that does not stick to alloy wheels. As a result, drivers find ceramics to be much cleaner. Ceramic pads are longer lasting than steel-based composites as the ceramic material wears more evenly.
Porsche Ceramic Composite Brakes
In the year 2000, SGL Carbon, the largest manufacturer of carbon and graphite products in the world, announced the startup of production for ceramic composite brakes in Meitingen, Germany. The Porsche brakes, used on all four wheels, are made of SIGRASIC, a light, hard and fracture-resistant, fiber-reinforced ceramic material. The ceramic brake disc weighs more than 50 percent less than the older, steel-based composite disc.
Additional Features of Ceramic Brakes
Ceramic discs have an extremely hard surface that produces a consistent level of friction during application while reducing wear on the rotors. Ceramics do not corrode and therefore remain unaffected by the salt found on North American roads in winter. The ceramic disc also has noise-dampening features not uniformly used in steel-based composites.
Noise Reduction and Wear Life
Angled or beveled edges on the front and back edges of the ceramic pad (chamfers) increase the clamping force of the pads against the rotors, thereby reducing noisy vibration. Slots cut vertically, diagonally or horizontally in the pads change any vibration that occurs to a frequency higher than can be detected by the human ear. Insulator shims provide a noise-dampening layer to further absorb vibrations that may produce noise. Durability tests have shown that ceramic brake pads last considerably longer than steel-based composites.
Ceramics cost more than conventional steel-based composites, but their longer wear, zero corrosion and quiet performance may offset the cost differential. It remains for the car owner to comparison shop and choose the brake pad that best suits his vehicle and where and how it is driven.
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