Hard like Diamond
It doesn’t rust and produces hardly any brake dust. The
Ever hear of WIDIA? Dr. Matthias Leber flashes a knowing smile. As a mechanical engineer and brake expert at the
Sounds like alchemy
What would happen if there were a brake that functioned nearly as well as a ceramic brake and had the same thermal stability but cost only about one-third as much, didn’t need racing pads, showed much less wear than a conventional gray-iron brake, produced hardly any brake dust, and didn’t rust? That sounds like alchemy—yet it’s serious technology from
New technology developed for racing is often transferred to road vehicles. One example would be the
Simply put, a brake disc made entirely of tungsten carbide would cost as much as several sets of ceramic brakes. Moreover, the technology wasn’t sufficiently advanced to bind tungsten carbide to a substrate—such as gray iron. But following a lengthy series of tests in close collaboration with Bosch/Buderus,
Searching for the right composite
“The pads required at least as much development effort,” says Leber. Laser technology and high-precision, automated production processes for a new type of disc are one thing. Pads with the right composite are another. A surface as smooth as a mirror needs a special pad that’s adhesive. Imagine running your finger with light pressure over a mirror; it doesn’t slide uniformly but instead keeps sticking for an instant. However, an overly soft pad on a very hard surface would wear down too quickly at high disc speeds. So the engineers added some very hard materials to the pad: microscopic particles that penetrate the tungsten carbide coating. These pads positively cling to the disc.
“The result surprised us all,” says Leber. “We already knew that the brake would be good, but the first tests exceeded all our expectations.” Thanks to the smooth surface, the full pad immediately starts covering the disc at low speeds. You could compare it to the difference between a vinyl record and a CD: unlike gray iron, tungsten carbide has hardly any grooves and is smooth as a mirror, so there are no hollows to reduce the total amount of surface area. When greater stopping power is needed at high speeds, the hard components of the pad throw out their microscopic anchors. “That, of course, means wear and tear,” says Leber. “It also means brake dust, but 90 percent less than what you’d get with a gray-iron brake.” Moreover, the tungsten carbide discs have a service life 30 percent longer than their gray-iron counterparts. This puts their performance levels close to those of the PCCB, but at only one-third of the cost of the ceramic brakes. And the new brakes feel like the PCCB in practice. The pedal force remains constant, even when the brakes are hot. These brakes don’t show the dreaded fading behavior at high temperatures. On the contrary, they work all the more crisply at temperatures above 600 degrees Celsius.
Clean as a whistle
After around six thousand kilometers of normal use, the brake pads have polished the surface of the disc to a shine. Their color then matches the white ten-piston fixed calipers in the front and the four-piston fixed calipers in the rear, whose technology is familiar from the PCCB. But why white? Leber laughs. “If a brake produces practically no dust, you want to advertise that fact. My color proposal met with a lot of initial resistance.” But after thousands of kilometers, the brakes on the new
The PSCB will start as standard equipment only in the new
By Thorsten Elbrigmann
Photos by Frank Ratering