Honda Car Forum

Mercedes cancels by-wire brake system; decision a blow to technology's
future

JENS MEINERS | Automotive News Europe
Posted Date: 12/8/05

Mercedes-Benz is discontinuing the twice-recalled Robert Bosch GmbH
braking system on the E-Class and CLS-Class sedans next summer in a move
that is a blow to automotive brake-by-wire technology.

Mercedes will drop the Sensotronic Brake Control system from the E-Class
in June 2006 when it introduces the car's midterm face-lift. At about
the same time, the E Class-derived CLS also will lose the system. Both
cars will have a conventional hydraulic braking system. "We can now
offer all the comforts of SBC in a conventional system," said a Mercedes
insider. "SBC was a very expensive system."

But the source also acknowledged that customers had lost confidence in
the system.

Software failure

The technology eliminates the mechanical link between the driver's brake
pedal and the brakes, substituting an electrical link that actuates the
brake calipers.

Customer complaints were linked to the failure of software for the brake
system. When the system failed, the hydraulic system took over. But that
resulted in a longer stopping distance and additional brake pedal effort
by the driver.

"Statistically, (the Sensotronic Brake Control is) as good as our other
braking systems and sometimes better," the insider said. "But we cannot
get the doubts out of customers' heads."

Mercedes' SL roadster and the low-volume SLR McLaren and Maybach
supercars will retain the brake system until the end of their life cycles.

It would be too costly to re-engineer those low-volume cars to
accommodate a conventional system, a source said.

Sensotronic Brake Control was supposed to highlight Mercedes' technology
leadership. Instead, it created a double blow to the brand's image.

In May 2004, Mercedes recalled 680,000 vehicles to fix the complex
brake-by-wire system. Then, in March 2005, 1.3 million cars were
recalled, partly because of further unspecified problems with the
Sensotronic Brake Control system.

$173 million price tag

Bosch has no other customers for the system, which it co-developed over
nine years with DaimlerChrysler AG at a cost of 147 million euros, or
about $173.3 million at current exchange rates.

A Bosch spokesman acknowledged that the system has lost some of its
competitive edge.

"In 2001 we were far ahead with SBC, but conventional technology has not
been standing still," the spokesman said.

"With the ESP Premium (vehicle stability system), we have all SBC
functions in a conventional system."