One of the main differences between ceramic-enhanced friction materials and semi-metallic brake linings is that ceramic pads contain no steel wool or fibers. Steel provides strength and conducts heat away from rotors, but it also makes pads noisy. Steel also acts like an abrasive and causes rotor wear. Substituting ceramic materials and copper fibers for steel allows ceramic pads to handle the high brake temperatures with less heat fade, to recovery quickly, to experience less wear on both the pads and rotors, and to virtually eliminate noise. Annoying brake squeal is eliminated because the ceramic-enhanced compound dampens noise and moves vibrations to a frequency beyond our range of hearing.
Other features that help make ceramic pads extra quiet include chamfers, slots and insulator shims. These features are also found on other types of pads, but may not be used on all applications.
Chamfers are angled or beveled edges on the leading and trailing ends of the pad that reduce "tip-in" noise when the brakes are first applied. Chamfers also reduce the surface area of the brakes slightly, which increases the clamping force applied by the pads against the rotors. This further helps to dampen sound-producing vibrations.
Slots are grooves cut vertically, diagonally, or horizontally in the pads to reduce noise by changing the frequency of vibration from an audible level to a higher, inaudible frequency beyond the range of the human ear. Slots also help reduce brake fade by providing a passage for gases and dust to escape at high brake temperatures.
Insulator shims provide a dampening layer to absorb and dissipate vibrations before they can cause noise.