The standard rear-axle steering with a steering angle of up to 4.5° contributes to the handy and dynamic impression of the EQS. Alternatively, the rear wheels can even turn in by up to ten degrees. This enables a turning circle of 10.9 metres. This corresponds to the turning circle of many models in the compact class. The variant with the large steering angle can also be unlocked later via an upgrade over the air (OTA). The respective rear-axle angles and trajectories are shown in the driving mode menu in the central display.
The interaction between the front-axle and rear-axle steering is configured to ensure agile responsiveness in urban and country traffic together with a very high level of stability. This results in e.g. small side-slip angles and a high level of yaw suppression. At high speeds the focus is more on stability, though without compromising precision and responsiveness. This added value is achieved by integrated actuation of the steering and brakes (ESP®), and considerably improves handling safety as a result.
The operating principle of rear-axle steering in detail: An electric motor drives a spindle at the rear axle via a drive belt. This makes axial adjustments to the spindle. Depending on the speed and the steering angle, the rear wheels turn in the same or the opposite direction as the front wheels (same direction or counter-direction). In simplified terms, this produces more agility and a smaller turning circle by counter-steering and more stability with same-direction steering. The environmental data of the vehicle sensors (radar, camera, ultrasonic) are used to adapt the maximum angle to the relevant situation. The system switches from counter-direction to same-direction steering at more than 60 km/h.