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A newly developed direct-steer system with variable power assistance is available on the face-lifted Mercedes SLK as an option (standard on SLK AMG 55).
The direct-steer system is derived from the previous speed-sensitive power steering and operates purely mechanically. This dispenses with the need for sophisticated actuator units and complex sensors. At the heart of the system is a new rack with ingeniously devised toothing that is designed to alter the steering gear ratio as the steering angle changes. Around the central position, the steering has an indirect ratio for good straight-line stability, resulting in better safety at high speeds. As soon as the steering wheel is turned to an angle of 5 degrees, the ratio increases rapidly and the steering feels far more direct. In this way, the number of steering wheel turns from lock to lock is reduced by around 25% with the new direct-steer system. Consequently, relatively small turns of the steering wheel are sufficient for changing course when driving in city traffic and high-speed twisty sections of country roads can be negotiated safely and precisely using relatively small steering movements. Porsche equips the 911 of this steering, but the ratio changes from 30°.
Yvonnick Gazeau |
