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How Porsche Built The Game-Changing Brakes On The 2019 Cayenne

On Monday, August 5th, 2019

Porsche’s new Surface Coated Brake system uses white calipers, a nod to the fact that the mirror-finish tungsten carbide-coated rotors drastically reduce brake dust.

Brakes

There’s usually a compromise between brake pad performance and brake dust (high-performance pads tend to generate more schmutz on your wheels) but that’s not the only reason Porsche bothers to zap rotors with high velocity oxygen fuel, a process that looks like an extremely one-sided lightsaber battle.

PSCBs offer some other bennies, which is important since they’re a $3,490 option on the Cayenne S, though they’re Standard on the Cayenne Turbo.

On the track or during hard driving—given that we’re talking Cayennes, trailering could be relevant, too—a system with iron rotors is going to experience some brake fade as the rotors heat up. During testing, Porsche executed brutal high-speed stops that took both iron rotors and surface-coated rotors up to nearly 1,200 degrees Fahrenheit.

Over the course of 13 stops, they measured the change in pedal force required to haul down the vehicle, and while both systems required a firmer squeeze of the pedal, the PSCB rotors only experienced half as much fade as the iron brakes. Fun fact: on the Vickers hardness test, iron has a value of around 30 to 80 HV. Tungsten carbide is above 1,000 HV, which is why it’s so popular for drill bits.

So why not just make the whole disc out of tungsten carbide? Well, because those rotors would make carbon ceramics look affordable. So instead, Porsche developed a three-part process to apply a 100-micrometer thick layer of tungsten carbide to an iron disc. The core of the rotor is thermally treated and roughed up with a laser to encourage bonding with the galvanically applied intermediate layer—think of it as applying primer before you paint a wall.

While the PSCB system is surely heroic on a track, I’d caution the less hardcore Porsche fans out there to take a drive before checking that particular option box.

Right now PSCB is available on the Cayenne only. Depending on how the system is received, perhaps shiny tungsten rotors will find their way elsewhere in the lineup. I bet a 911 would look good with white calipers.

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