High-performance brake systems are moving forward along multiple paths at the same time. One path is to develop simpler, lower-cost components that meet price constraints for medium-priced "street" cars. Another is making the highest technology available for premium automobiles, not just "ultras." A third, straddled between those, is weight reduction.
A complete Brembo system on the Hyundai Genesis Coupe since 2010 is an example of a high-performance brake brand moving into the medium-price market—with four-piston fixed calipers, ventilated rotors, and Brembo's own low-metallic/NAO (non-asbestos organic) brake pads. Yes, the system is only on R-Spec and "Track" models with the 3.8-L V6, the higher-performance editions of the street car. On those it ranks as a major upgrade vs. the single-piston floating caliper system on 2.0-L turbo coupes.
When it comes purely to shortest stopping distances, the premium brake systems do contribute, but the effect of the tires is a greater factor, notes Brembo engineering. The braking system's real contributions are in overall braking effectiveness, including pedal feel and freedom from fade, and even more uniform lining wear from the greater stiffness of the one-piece, multipiston aluminum calipers. These also reduce system hysteresis and improve ABS response vs. the floating caliper system.
And, of course, the advanced, lighter high-performance brake systems reduce vehicle unsprung weight.
However, the effect on braking distance also was apparent when a Lamborghini Gallardo with carbon-ceramic rotors (the road-racing choice for ultralightness) tied for first at 32.6 m (107 ft) in a German magazine test of braking distances (100 to 0 km/h [62 to 0 mph]), and carbon-ceramic equipped cars took seven of the top 11 spots.
The bright-paint calipers, typically red but also in silver, black, yellow, and blue, are the most obvious sign of the premium system. They're all fixed caliper with four to eight pistons depending on rotor/wheel size. Brembo uses different diameter pistons for the larger calipers, even asymmetric location, to compensate for tapered lining wear that otherwise would occur on hard braking.
Most of the calipers, which Brembo now also makes in a U.S. Hayes Lemmerz plant acquired in 2007, are one-piece designs. The ultrapremium—made of machined billet—is the racing choice. The higher volume, lower cost (as on Genesis Coupe) are cast calipers, using sand core technology. They are comparably stiff (similar Young's modulus), but billet is lighter because more metal can be removed during machining. Brembo also supplies a two-piece caliper, its lowest-cost design. Manufactured with stainless steel bolts, it forms an assembly that Brembo says is "close" to the stiffness of the one-piece.
The Genesis Coupe rotor is a solid cast-iron design, about 1 kg (2.2 lb) heavier than a two-piece cast-iron with an aluminum hat. The Brembo two-piece rotors, with slots or drilled holes, plus fixed calipers, have more "eye appeal" as true performance choices. Although the primary function of holes and slots was to vent gas emissions from the linings, that's not a major issue with today's lining materials. However, the company's engineers have found that they provide a 3-5% overall improvement in braking vs. a solid surface rotor, enough to keep them in preferred use for certain high-performance applications, despite some possible reduction in pad and rotor life, and minimal effect on rotor weight.
Carbon-ceramic rotors with aluminum hats are the heart of "super brakes." They first appeared on the 2001 Porsche 911 GT2, and today Brembo says they account for 3% of the ultrahigh-end market and are in most road-racing cars. Brembo sees market share increasing to 25% within three years. How many systems does that percentage mean? Brembo won't say, but current production reportedly is about 35,000 systems, and carbon-ceramic also may be found on Bentley, Bugatti, Lamborghini, Aston Martin, Ferrari, some Audi, Mercedes-Benz, and BMW models. The near-future production target is believed to be nearly a quarter-million. The only American car with carbon-ceramic is the Chevrolet Corvette ZR-1.
To reach the target, Brembo must manufacture the discs faster than the nearly-a-month "batch" system currently in use and find some way to turn what involves custom labor into a series production line. Production also could be simplified if process temperatures could be lowered from the present peak of 1700°C (3100°F), according to Brembo engineering, and it's working to that end.
Present cost (about $11,000 as an option price) is high, but racing cars and ultrapremium cars put price tag of functional components well down the list of what's important. To get carbon-ceramic pricing into at least the premium end of the mainstream, Brembo is in a joint venture with composites manufacturer SGL Group.
The appeal of carbon-ceramic is a consistently high coefficient of friction with low wear, and fade-free operation at the extremely high temperatures that may be encountered in racing, along with a significant saving in weight.
Weight reduction is hard to quantify, because it varies according to the design and aspects of manufacture and what the manufacturer views as the package. With the brakes alone, Porsche reportedly saw a 50% saving. Other manufacturers have seen less, and if they look at the entire assembly (including spindle and hub, etc.), the savings over cast-iron might be only 13% (estimate for the Nissan GT-R) to as high as 30% (for the Aston Martin Virage). However, as with any technology, there are continuous improvements, and Brembo said that the Ferrari F142, with ceramic pads, saw a weight saving of 10% vs. the previous carbon-ceramic system it used.
Brembo also sees an aftermarket presence for carbon-ceramic brakes, where desire for the best can overcome price-sensitivity. At present, it has the GT-R aftermarket line of two-piece (cast-iron/aluminum hat) rotors with four-piston and six-piston billet calipers for some high-performance street applications, including Porsche, Ferrari, BMW, Corvette, and new Camaros.
Among the vehicles for which it is considering carbon-ceramic add-on kits are those makes, plus Lexus ISF and LFA, Nissan GT-R, Buick Regal GS, all Chrysler SRT models, Ford Mustang GT350, Boss 302, and Shelby GT500, and Cadillac CTS-V and the upcoming ATS. The CTS-V presently has a cast-iron rotor with an aluminum hat.