Mercedes drops brake-by-wire project - technology may not recover

By Jens Meiners, Automotive News Europe

Mercedes-Benz is discontinuing its twice-recalled Robert Bosch-supplied braking system from the E class and CLS class next summer in a move that apparently dooms automotive brake-by-wire technology.

Mercedes will drop the Sensotronic Brake Control system from its E class medium-premium sedan in June 2006 when it introduces the car's mid-term face-lift. About the same time, the E class-derived CLS sedan will also 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 brake system.

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

"Statistically, [SBC is] as good as our other braking systems and sometimes better," the insider said. "But we cannot get the doubts out of customers' heads."

A double blow

Mercedes' SL class premium roadster and the low-volume SLR McLaren and Maybach supercars will retain SBC brakes until the end of their life cycles. It would be too costly to re-engineer these low-volume cars to accommodate a conventional system, a source said.

The system 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 had to be recalled -- partly because of further unspecified problems with SBC.

Euro147 million technology

Bosch has no other customers for the SBC system, which it co-developed over a nine-year period with DaimlerChrysler at a cost of E147 million.

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

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

"In 2001 we were far ahead with SBC, but conventional technology has not been standing still," he said. "With the ESP Premium [vehicle stability system], we have all SBC functions in a conventional system."

From Automotive News Europe (A Crain publication)