Designers unlock the secrets of brake squeal01 November 2007
Most people, even experienced chassis engineers, believe brake squeal emanates from the contact of friction material on the disc. In reality it is more complex than that and often involves amplified vibrations from the calliper and other system components, writes Roger Bishop.
Federal Mogul's research and development team in the USA, responding to a market request for quieter braking performance, studied the phenomenon in detail and came up with an innovative solution now being offered to the aftermarket. However, the intention is to make it available to the OEM sector, particularly for higher end vehicles where the 8 to 10% cost penalty for a set of brake pads can most easily be absorbed.
In a conventional brake pad a shim is inserted between the backing plate and the housing that holds the pad within the brake assembly to absorb sound and dissipate heat. The shim and backing plate are attached with rivets or an adhesive, meaning there is a possibility of unwanted shim movement within the pad assembly.
Federal Mogul's ThermoQuiet design involves a backplate through which four or five holes are drilled. During manufacture, the friction material extrudes through the holes while from the other side a phenolic-based integrally moulded insulator fuses with the friction material and flows over the non-working side of the backplate to a thickness equivalent to the normal shim. This allows the brake pad to directly replace standard components.
Seamlessly integrating the shim, friction material and backplate into a single unit in this way creates a strong mechanical lock and provides a greater surface area for dissipating heat and noise.
The ThermoQuiet development recently took first prize in the prestigious Grand Prix Awards at the EquipAuto exhibition in Paris.
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