Differences Between Carbon/Carbon and Carbon Ceramic Matrix Brakes

Chris from Brake Pros wrote a great clarification on the differences between carbon-carbon and carbon ceramic matrix brakes.   STILLEN and AP Racing have a 400mm CCM brake upgrade for the R35 Nissan GT-R. Not only are the CCM brakes larger than stock, they are 38 lbs lighter than the factory brakes. This is unsprung and rotating weight that is removed from the driveline. In a car as heavy as a GT-R it is a great way to improve performance.

There is a lot of confusion out there when people hear "carbon brakes". In racing, carbon-carbon (C-C) is used wherever the rules allow it. For high-performance road vehicles, carbon-ceramic matrix (CCM) is the rotor of choice. Carbon-carbon brake systems consume both the rotor and the pads, where CCM brakes are designed to consume only the pad.

There are a few different ways to make CCM rotors. The ones on the Scuderia you mention are made from three pieces, a chopper-gun-like core and two face plies -- and only those face plies are siliconized into carbon-ceramic. The core remains C-C. So far, this style of construction is more delicate and less user-friendly than a full 3D CCM, like those on the STILLEN GT-R upgrade. The 3D version takes longer to make and requires more energy, so they end up being more expensive.

The enemy of CCM brakes is not wear -- they are very, very hard (approaching diamond hard!). The real issue is oxidation. As long as rotor temps are kept below 750°C / 1400°F, they could possibly last the life of the car or even longer. If run for extended periods of time over that temperature, oxidation will start to convert the carbon molecules to carbon dioxide, which just floats away. So it pays to keep track of rotor temps, which is why we apply paint temps at STILLEN before we assemble them to the hats. Cooling kits are a great idea for track use. Keep in mind that the pads will also run hotter as the rotor has less mass to absorb braking energy than iron discs, so the CCM discs will heat up everything around them a bit more.

Now here is another interesting point: If you were to oxidize those Scuderia CCM rotors (or the ones on any Ferrari, Lamborghini, Porsche, Aston Martin, Audi, ZR-1 Corvette, etc.) you get to throw them away after they lose a prescribed amount of mass. With the Stillen GT-R system, surface oxidation can be ground off to where the rotor looks like new again. This can only be done with a full 3D CCM rotor, not the 3-piece laminated type like on the other cars mentioned above as you would grind right through the thin face plies!

If we chose to go with the 3-ply route instead of 3D, we could probably lower the price a couple grand -- and then have to deal with the occasional dissatisfied customer who would have to replace a front pair when they were excessively oxidized or if damaged by putting wheels back on the car. In the service manual for the ZR-1, the service tech is required to place a foam ring around the rotor before removing a wheel. If not, the dealership gets to pay for a new rotor if he chips it. While I certainly don't recommend pounding a wheel against the STILLEN/AP Racing CCM rotors, we are much less concerned about careful, routine service creating such a problem.

Even though carbon-carbon has been around since the 70's (I started working with C-C in 1990), the more recent availability of CCM to the general public will continue to cause confusion until we get further down the road. They are not the same as iron in any capacity other than they are roughly the same shape. We can't expect that after 100 years of iron drums and discs that CCM technology will be completely understood by the masses for quite some time. Then add the fact that they are still changing as companies continue to look for ways to reduce the manufacturing costs.

Source: NAGTROC forums