Porche Cayenne Brakes

You've got your iron rotors, your carbon ceramic rotors, and now these: tungsten carbide coated rotors, which offer some of the advantages of both.

Cayenne Turbo Specs: Engine: 4.0-liter twin-turbo V8, 541 hp and 568 lb-ft of torque / Transmission: eight-speed automatic / Top Speed: 177 mph/ Ground clearance: 9.6 inches (air suspension, high level) / 0-60: 3.7 seconds / Tow rating: 7,700 pounds /Base price: $126,500

The white calipers are a baller move.

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. 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.

As for the PSCB's lack of fade, that because of the unique interplay between the glass-smooth rotors and the specially formulated pads. Since the rotors are so smooth, the pads effectively apply more surface area to the rotor than they would with an iron disc. And under high braking pressure, the pads dig into the rotor surface like a microscopic hook-and-loop fastener—abrading the rotor and generating some dust, but delivering massive stopping power, too.

Depending on how you drive, Porsche says PSCB creates 90 percent less brake dust and your rotors should last 30 percent longer. And, as expensive as it is, the PSCB option is still about a third the cost of the carbon-ceramic setup. As with the carbon brakes, you get 10-piston front calipers and 4-piston rears. Also like the carbon brakes: no rust on your rotors—ever.

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.

Then comes the main event, the high velocity oxygen fuel spraying process, in which tungsten carbide particles are fired at the disc at supersonic speeds. And yes, that looks as cool as you'd expect. The mirror finish arrives after about 4,000 miles of driving, since the process depends on the pads polishing the rotors.

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. That's because the surface-coated brakes, with their enormous calipers and super-grippy pads, almost feel like they deliver more stopping power than you can use in normal driving. Around town, you learn to go light on the brake pedal, lest all loose items in the car take a speedy trip toward the windshield and footwells. You get used to modulating the pedal differently than you would in a car with iron, or even carbon ceramic, rotors.

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.

Ezra Dyer is a Car and Driver senior editor and columnist. He's now based in North Carolina but still remembers how to turn right. He owns a 2009 GEM e4 and once drove 206 mph. Those facts are mutually exclusive.

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