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March 18, 2011

News & Features

'Superbrakes' are stronger, longer lasting and coming down the road

New York Times News Service

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Carbon-ceramic brakes, like these for the 2011 Chevrolet Corvette ZR1, are long-lasting and light-weight. But they're also very expensive. (General Motors)

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Carbon-carbon rotors have been used on Formula One racecars for decades. (The Associated Press)

For more than 30 years, Formula One racecars have benefited from powerful brakes that vastly outperform the systems available on any showroom model. The gap may be narrowing, though: High-tech materials similar to those on the racetrack began showing up in exotic sports cars about 10 years ago, and some luxury models now offer them as well.

How about the rest of us? Even underpowered grocery-getters would gain safety and weight advantages with advanced brakes. Until costs drop, we'll be waiting awhile longer, but the technology is here now.

"Superbrakes" come in two varieties, and the rotor -- the disc of disc brakes, which is squeezed by the brake pads to slow the car -- is the key part of each.

Carbon-carbon rotors, a composite of carbon fiber and carbon, made the first great leap in stopping performance. Used mainly on racecars, where they first appeared in the 1970s, they are not well suited to road use because of rapid wear and the need to operate at high temperatures. And they are expensive.

Price of progress
  • Why aren't automakers putting carbon-ceramic brakes on every vehicle? In a word, cost.
  • While the carbon-carbon brakes used on Formula One cars are hideously expensive, carbon-ceramic brakes are merely outrageously expensive: They're an $8,000 option on selected Porsche models, and $12,500 on the Mercedes-Benz SLS AMG.
  • Although the silicon carbide and carbon fiber used to make the rotors are not that expensive, the manufacturing process is costly. The rotors have to be baked at a very high temperature for several days in special ovens. Production is limited by oven capacity and by the time it takes to cook them.
  • Brembo SGL Carbon Ceramic Brakes of Milan, Italy, produces many of the carbon ceramic rotors used on production vehicles. Roberto Vavassori, the business development director, says the company hopes to whittle down the cost.
  • While Brembo is actively working to improve the five-day manufacturing process, he says, he does not see carbon ceramic brakes coming into wide use for another decade.

Carbon-ceramic rotors, a composite of carbon fiber and silicon carbide, could be the superbrakes for the rest of us. They were developed for high-speed trains in the 1980s.

In 2001, the Porsche 911 Turbo introduced carbon-ceramic brakes to road-going automobiles. Now, they are available on the Chevrolet Corvette and on top models from brands including Aston Martin, Audi, Bentley, Bugatti, Ferrari, Lamborghini and Mercedes-Benz.

These carbon-ceramic brakes would be a boon for owners of economy cars driven mostly in the suburbs. For one thing, brake rotor replacement would become a thing of the past, as the carbon-ceramic rotors -- which are extremely hard and wear minimally -- might well outlast the car. Tadge Juechter, chief engineer for the Corvette, says that carbon-ceramic rotors "last basically forever in street use."

More important, vehicle weight would be reduced significantly, because a carbon-ceramic rotor weighs about 40 to 50 percent less than a cast-iron rotor. Chevrolet spokesman Dave Caldwell says the carbon-ceramic rotors used on the Corvette ZR1 were each 11 pounds lighter than the corresponding metal rotors of other Corvette models.

The overall weight savings exceeds that achieved by the rotor swap alone, though.

Juechter says that because a carbon-ceramic rotor is lighter than an iron part, the heft of the suspension that controls it, and of the body structure to which the suspension is attached, can be reduced. So the overall vehicle weight savings could be considerable.

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