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The new Mercedes-AMG SL: the active rear-axle steering
For the first time in its long history, the SL is equipped with active rear-axle steering (HAL) as standard. Depending on the speed, the rear wheels steer either in the same or in the opposite direction of the front wheels. The system, which is precisely tailored to the new SL, enables both agile and stable driving behavior. Further advantages are the easier vehicle controllability in the border area as well as less steering effort, because the ratio of the front wheel steering of 12,8: 1 (instead of 14,2: 1 without HAL) is more direct.
The heart of the system are two electromechanical steering actuators (electric motors with spindle drive) that have no mechanical connection to the steering wheel. They replace the conventional toe links on the rear axle. This “by-wire” system, electronically controlled, adjusts the rear wheels in a predefined map. The toe angle change is up to 2,5 degrees on the rear wheel in one direction.
Up to a speed of 100 km / h, the rear wheels are turned in the opposite direction to the front wheels. This corresponds to a virtual shortening of the wheelbase. Advantage: the SL is much more agile when cornering, requires less steering work and is therefore even more enjoyable to drive. Further advantages are the increased maneuverability and the reduced turning circle in daily driving situations - such as when turning or parking.
If the SL drives faster than 100 km / h, the system turns the rear wheels parallel to the front wheels (maximum steering angle then 0,7 degrees). This corresponds to a virtual extension of the wheelbase and noticeably improves driving stability. At the same time, the lateral force on the rear wheels builds up significantly faster when changing direction, which speeds up the response to steering commands.
The active rear-axle steering not only improves handling in curves, but also supports the driver in sudden evasive maneuvers, thus increasing active safety. This makes the SL easier to control at the limit.
The response behavior is also dependent on the AMG DYNAMIC SELECT drive program: In Sport +, for example, the rear-axle steering reacts even more agile and directly at lower speeds. It also supports the optional automatic parking and the remote parking function. Later updates "over the air" are also possible.
