Coherent explanation of AWD system on E70s

[JCL]

Originally Posted by chiefneil

I thought BMW had some sort of system that could over-drive the outside rear wheel to reduce understeer? Is that a different model, or different manufacturer completely?

That system is called Dynamic Performance Control. It applies only to the rear wheels, and produces a form of torque vectoring by the use of a planetary gearset with clutch plates within the rear differential. By applying the clutches one wheel can be 'overdriven' based on commands from the controller. This system is only available on the X5M, X6M, and X6.