BMW Tweaks Active Steering

BMW AG won't exactly admit its high-tech Active Steering system had some bugs, but executives and engineers quietly concede the much-debated advance over conventional variable-ratio power steering has been “recalibrated” to improve response and “feel.”

Wolfgang Epple, BMW 3-Series program director, says the newly revised Active Steering debuts with the '06 3-Series.

Active Steering uses a supplemental, motor-driven gearbox to increase or decrease the amount of assist from the conventional hydraulic power-steering unit. The system is designed to add a level of responsiveness appropriate to the driving situation. In low-speed maneuvers, such as in parking garages, Active Steering “boosts” the ratio of standard power-steering assist, meaning the driver does not have to turn the wheel as much as usual.

Another boon is Active Steering's ability to coordinate with other electronic systems onboard. In a skid, for example, Active Steering takes information from the stability control system and can automatically countersteer to correct the situation.

Active Steering debuted to mixed reviews in 2003 with the 5-Series. Critics said the system improved low-speed handling but contributed to vagueness immediately after turning the wheel off-center and for feeling cumbersome and artificial during sporty, higher-speed cornering.

“We've improved ‘feel’ quite a bit from the 5-Series,” says Epple. He adds the revised system also will be fitted to the '06 5-Series beginning in September.

BMW developed Active Steering with ZF Linksysteme, a joint venture between German suppliers Robert Bosch GmbH and ZF Friedrichshafen AG.

Some cited Active Steering as evidence — along with the widely criticized i-Drive control system — BMW was allowing electronic innovations to blur its hallowed focus on perfecting the direct connection between man and machine.

But few would argue antilock brakes or automatic transmissions have been retrograde steps in automotive development.

That, too, will be the case with Active Steering, Epple believes. He says steering feel is subjective, and that many customers liked the first-generation Active Steering system.

In Germany, he says, customers exceeded the company's expected demand for Active Steering by more than 50%. BMW predicted a take rate of about 20% — but it has run upwards of 35%, says Epple.

There is an important distinction for Active Steering's presence on the 3-Series, however. Because the compact 3-Series traditionally has been the sportiest BMW sedan, it sometimes appeals to the most intense drivers, says Ken Bracht, 3-Series product manager, BMW of North America LLC. For that reason, BMWNA decided to “de-couple” Active Steering from the car's optional Sport Package, making Active Steering a standalone option ($1,250).

BMWNA planners thought it better to offer the Sport Package without Active Steering, so hard-core drivers skeptical of the system would not be forced to take it with the $1,600 option group. De-coupling Active Steering from the Sport Package also helped BMWNA to better manage the new 3-Series' sticker prices, he adds.

Meanwhile, Bosch and ZF say their joint venture may have another customer for the technology in the near future.

“We have customers that are close to ramping up,” Bernd Bohr, chairman of Bosch's automotive group, tells Ward's during a recent media event in Boxberg, Germany.
— with Tom Murphy