January 19th 2007.

One gripe that always comes to the fore whenever we do a brake job, is the fact that the brake discs are non machinable
and have to be replaced.

People always find it incredible that discs that were new only eighteen months ago are now beyond repair.

The problem, as always, is rust build up in the centre of the disc that stops the cooling fins from pumping air, causing the
discs to overheat and therefore, to distort.

Machining such discs does very little good, since this does not remove the rust in the centre of the disc and now the steel
is thinner and without any cooling, even more susceptible to warpage, which causes severe brake pedal vibrations.

It's quite likely that in a dry, always warm, atmosphere as we find in Arizona, discs will last longer, but from Fargo to Chicago
to Montreal, wherever ice melting rock salt is used, brake systems take a real beating from corrosion.

Fortunately, the cost of high quality discs has been cut in half over the last ten years and now the cost of a new disc, on the average
new car, is not much more than the cost of technician time on a lathe to machine the old ones.

I've always wondered if other, non rusting materials, could not be found, although I know that stainless steel is not an option, due to
its' galling tendency. It is a very difficult material to machine properly and it's obvious that its metallurgical characteristics disqualify
it for use as a friction surface.

Now, finally, the high tech ceramic discs have started to become noticed and although I may never see it happen, the non rusting,
"lifetime warranted" disc may be on the horizon.

Carbon-ceramic brakes have built a glamorous reputation in Formula One racing, creating vivid images of discs glowing red
during hard braking at the end of long straightaways.

Their high cost limited them to exotic performance cars. But carbon-ceramic brakes are now available on cars priced
as low as 60,000 euros (about US$80,000 at current exchange rates). And a new manufacturing process could make them
affordable for even budget-minded enthusiasts.

The technology has been slow to spread to production vehicles since it was introduced in racing 15 years ago.

Porsche first offered a carbon-ceramic brake option on the 911 GT2 in the late 1990s, followed by the more
mainstream 911 Turbo in 2000.

Today, carbon-ceramic brakes are optional on all Ferraris, most Lamborghinis and Porsches and the Bentley Continental GT
These cars are priced above US$133,000.

The percentage of buyers choosing this option ranges from more than half for Ferrari models to 6 percent for the Audi RS 4.

For enthusiasts, the performance-driving benefits -- less weight, better handling because of reduced unsprung weight
(the mass of the body and components not supported by the suspension), durability and fade resistance -- make the high
price worthwhile.

But if the price falls dramatically, carbon-ceramic brakes also could appeal to more thrifty buyers.

Carbon-ceramic brake discs last four times longer than conventional steel discs, so owners are unlikely to replace
carbon-ceramic discs. Brake pads last longer on the carbon-ceramic systems, too. But at $50 to $60 a disc for steel
discs and $665 to $2,660 a disc for carbon-ceramic, owners cannot recoup their cost on the more durable system.

The big step

SGL Carbon AG, of Wiesbaden, Germany, and Audi AG are trying to reduce manufacturing costs for carbon discs
by moving from batch production to a continuous process.

Since last year, Audi and SGL have been working to establish automated production and the cost of a disc will come
down to 350 euros (about $465) with the new process.

Audi declined to comment on the technology.

Antonio Ferreira, manager of European component forecasts at CSM Worldwide in London, is skeptical of carbons
broader market potential, even with reduced costs.

"You would need huge volumes to get the price down," he says. "Suppliers would have to come to a two-digit price (per disc).
Nothing else is feasible when a complete braking system is not even into three figures."

At Italy's Brembo, which has a 60 percent market share in top-end sports- and luxury-car brakes, carbon-ceramic is still
in a "quasi-prototype" phase.

Light and durable

But Vavassori is optimistic, saying the technology's lower weight and long life could become as important as its
extreme performance.

"We haven't seen the full potential for carbon brakes yet, they can save 40 kilograms (88 pounds) on an extreme car
where mass is important. And in the future, we may see wider adoption in other segments, too."

The key to lowering costs is simplifying production.

"It's not mechanical but chemical," said Brembo's Vavassori. "We start from powders and end up with a lightweight disc,
but an expensive one."

Versions of the carbon brakes for cars must be even more sophisticated than those on airplanes or race cars.
The process is similar to how nature creates coal and extremely hard substances like diamonds, some processes are
lengthy, demanding three weeks in the chamber to go through a thermal cycle.

How it works

Carbon-ceramic brakes use the same principle as ordinary disc brakes. Stationary twin calipers clamp onto both sides
of a disc rotating next to each wheel of a car, slowing it by friction.

The energy of the car's momentum is transformed into heat at the point of the friction, so brakes can get extremely hot.
Carbon-ceramic brakes use carbon fiber and ceramic materials that are stable at temperatures that would make steel
discs bendable. Performance doesn't diminish, leading to fade, with repeated use.

Carbon-ceramic brakes also typically use larger calipers to spread the clamping force over a wider area, improving
braking performance.

Race-car brakes must be warmed before they work properly. For passenger cars, carbon-ceramic brakes must be fully
effective immediately. The discs and brake pads are more sophisticated, with carbon fibers arranged to strengthen the
disc and conduct heat away from the surface.

Bentley:  A demanding case:

Weighing 5,258 pounds and capable of 198 mph, the front-engine Bentley Continental GT has almost certainly the most
demanding braking task of any production car.

Midengine cars such as the Bugatti Veyron have it easier. Their weight distribution means that all four wheels can share
more of the braking effort. On the Continental, the front brakes do most of the work.

The Continental GT already had the biggest brake discs in the industry at 16.2 inches. and now they've broken their own
record, with a 420-millimeter (16.8-inch) carbon-ceramic disc, which is half the weight and gives lower unsprung and
rotating masses.

The ceramic brakes also have superior fade resistance and improve steering precision. Pad life has tripled, and discs
should last the life of the car.