Why do car manufacturers use different types of materials for brake discs? I have heard of the carbon-ceramic disc and now Porsche has something called a surface-coated disc.
Most brake discs are made of cast iron. This material has good friction properties and, because it has been developed consistently over the decades, is the cheapest.
Carbon-ceramic brake discs are a standard feature on Formula One cars and most other race-prepared cars these days. Besides being almost 50 per cent lighter than iron discs, carbon ceramic has a huge advantage when it comes to wear resistance, stability and consistency at the high temperatures and heavy use that race-car brakes are subjected to.
On a few high-performance road cars, carbon-ceramic brake discs can be specified, but they come at a price. Hence such an option is usually available only on high-end performance cars.
Besides the prohibitive cost, these brakes also perform their best at high temperatures, making them less than suitable for normal road use.
Porsche's new surface-coated disc, also known as the Porsche Surface Coated Brake (PSCB), is made from conventional cast iron, but goes through an additional process during manufacturing.
A coating of tungsten carbide is applied throughout the surface that makes contact with the brake pads. In terms of cost and performance, the PSCB sits midway between the normal cast-iron disc and the carbon-ceramic type.
The most interesting aspect of the PSCB is its permanent mirror-like surface once the disc is run-in and the absence of brake dust on the wheels.