What Is the Difference in Ceramic & Non-Ceramic Brake Pads?
Brake pads and shoes have come to be marketed just like any other automotive component, with slick ad campaigns, performance claims and reliability promises. This is evident in brake pad and shoe construction, with several designs available to the consumer: ceramic, semi-metallic and low metallic, organic and, to a lesser extent, asbestos. To understand how ceramic brake pads differ from others, a definition of each is needed, and an explanation of how each type affects performance, reliability and wear.
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Ceramic Brake Pad Construction
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Ceramic brake pads are constructed with ceramic fibers, nonferrous materials, bonding agents that act as adhesives, like strong resins, and small amounts of copper fibers (15 percent) that add strength and rigidity. Their dust color is lighter than other non-ceramic pads, and they contain chamfers and slots, like most other pads. Chamfers are beveled edges on the pad ends that quiet "tip-in" noise upon brake pedal application. Slots are grooved channels, cut diagonally, vertically and horizontally into the pad surface, which moves dust and moisture away. Unlike other types, ceramic brake pads contain no asbestos or steel fibers in their construction.
Ceramic Brake Pad Performance
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Unlike metallic and semi-metallic pads, the softer materials in ceramic pads promote longer wear life on rotors but slightly more wear on the pads. They produce less visible dust during wear; the dust that remains is lighter in color and less likely to adhere to alloy and metal wheels. The cushioning effect of the ceramic construction allows for a quieter ride, less prone to produce brake squeal, because vibration and frequency ranges exist beyond the capability of the human ear. Ceramic pads can handle higher brake temperatures, which reduces brake fade. Overall, ceramic pads offer a more consistent and comfortable brake feel at the pedal, but sacrifice in the area of higher costs than all other types.
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Semi-Metallic and Low-Metallic Brake Pad Construction
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Semi-metallic pads consist of numerous metal fibers in their construction, such as brass, copper and steel. The formula can also contain wire bits, steel wool shavings, graphite and copper, depending upon the manufacturer. The ingredients are bonded together by strong friction modifiers and organic fillers, forming an adhesive resin. The ratio of metal in semi-metallic pads ranges from 30 percent to 65 percent. Low-metallic pads contain an organic formula of steel or copper, in amounts of 10 percent to 30 percent. Ceramic pads contain none of these ingredients, with the exception of small amounts of copper.
Semi-Metallic and Low-Metallic Brake Pad Performance
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Semi-metallic and low-metallic brake pads have the highest wear proficiency over all other types, with the low-metallic pads having the least of the two. They both transfer heat adequately, but not as efficiently as ceramic types. The pads wear longer, due to their metal reinforcement, but typically wear out rotors much faster than ceramic pads. When overheated, or during low speed brake application, metallic pads can create brake squeal, and sound noisier during normal driving applications. They perform less favorably during low temperatures, and often have a harsher feel to the brake pedal. Metallic pads cost less than ceramic pads, and are suited to heavier-duty car and truck applications. Metallic pads produce more dust, due to their steel and carbon makeup.
Organic Brake Pad Construction and Performance
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Organic pads, sometimes called non-asbestos or NAO, contain material fibers of rubber, carbon, glass and Kevlar. Filler materials and high-temperature resins bond the material fibers together. These pads are softer than the metallic and ceramic types, and often cited as the most quiet type of pads. They wear relatively fast and create more brake dust than the ceramic types. Due to the softness of the pads, their braking characteristics remain smooth, with even and consistent braking contact.
Asbestos Brake Pads
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Asbestos brake pads contain compacted fibers of heat-resistant asbestos, filler and adhesive resin compounds. Although asbestos lining has been generally phased out, after-market lining and pads are still available, and some vehicles still use these pads and shoes as standard equipment. With the introduction of front-wheel drive during the early 1980s, asbestos pads and shoes could not combat the high brake rotor temperatures, and were replaced with metallic varieties. Asbestos, although cheap and performance efficient, became outlawed in some countries because of the health risks associated with respiratory ailments and lung cancer.
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References
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