High Speed Range

As the vehicle speed increases, the degree of steering angle amplification by the Active Steering component is reduced. The steering-gear ratio becomes less direct.

At the same time, the steering strategy adopted by the Integrated Active Steering changes. Whereas, at low speeds, the rear wheels are steered in the opposite direction to the front wheels, at higher speeds the rear wheels are steered in the same direction as the front.

The momentary axis moves further back, equivalent to a vehicle with a longer wheelbase, producing more stable straight-line handling. The radius of the curve becomes longer.

By the combination with the Active Steering, an additional amount is added to the steering angle of the front wheels so that the radius of the curve and the required amount of steering lock remain at the familiar level.

Fig 1: Identifying Variable Steering-Gear Ratio - High Speed Range

Courtesy of BMW OF NORTH AMERICA, INC.

All in all, co-ordination of the steering interventions at front and rear makes lane changes and steering maneuvers considerably easier to negotiate without sacrificing agility or balance.

Combination of the Active Steering with the new rear-wheel steering system offers benefits for the driver at all speeds.

Fig 2: Identifying Variable Steering-Gear Ratio - High Speed Range (Effective Wheelbase Increase)

Courtesy of BMW OF NORTH AMERICA, INC.