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From YourSITE.com Audi News
Audi is introducing a new brake technology for series-production vehicles for the first time. The 12-cylinder A8, the flagship model of the Ingolstadt brand, can be equipped with ceramic brakes as an option. Compared with conventional steel discs, these not only last four times longer, but also offer high braking performance, even when driving at the limit, as well as maximum resistance to fading. The significant reduction in weight also leads to advantages in terms of comfort and handling thanks to reduced unsprung masses. The innovative brake discs are manufactured from carbon-fibre reinforced ceramic, a material which has proved itself time and again in aviation and space travel. The raw material used to make this compound – known as composite ceramic – is the very hard and abrasion-resistant silicon carbide with a diamond-like crystal structure and high-strength carbon fibres embedded in it, and these effectively absorb the stresses occurring in the material. The high-tech material provides a whole array of benefits. Its resistance to corrosion is plain to see; ceramic brakes do not allow even the beginnings of rust to form on the brake discs. A clear indication that ceramic brakes are fitted is provided by their sporty appearance, with the characteristically arranged perforations and red brake callipers. The technical advantages are principally concerned with weight reduction. Firstly, for example, weight is reduced by five kilograms – or around 50 per cent – per wheel. This considerably reduces the unsprung masses at the wheels and consequently leads to an even higher standard of ride comfort. Driving dynamics also benefit from the lower weight of the brake unit. The high abrasion resistance of ceramic discs means that they will last for up to 300,000 kilometres in everyday use – four times the lifespan of a steel disc. Over this distance they will wear by a mere 0.5 millimetres. The performance of the ceramic brake system also benefits from clear progress. The brake discs ensure a very high braking performance even at the limit. Resistance to fading – a clear deterioration in performance after repeated braking, typically occurring when driving down mountain passes, for example – is far superior to that of other types of brake. For sporty, high-performance vehicles such as the 12-cylinder A8, this means a palpable increase in safety reserves. The driver also experiences the qualities of the ceramic brakes subjectively in terms of their clearly defined pedal feel under all operating conditions. Furthermore, brake judder never becomes an issue for the innovative brake discs, whatever the operating status. 380 millimetre ceramic discs are deployed on the front axle in combination with 19-inch wheels. The rear disc has a diameter of 356 millimetres. The ceramic brake disc ring is bolted to a stainless steel chamber via ten resilient connecting elements, which makes connection to the wheel hub possible. The elaborate cooling duct geometry of the ventilated brake discs ensures optimum cooling of the brake discs. Firm grip on the brake disc is guaranteed at the front by 6-piston monobloc brake callipers from Brembo, and at the rear by floating-calliper brakes. As on the other A8 models, the electromechanical parking brake is part of the standard specification. The new ceramic brake has been available since July 2005 for the 12-cylinder A8 W12 and A8L W12 quattro models. The optional ceramic brake can be ordered for 8,000 euros.
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