From Reference documents:

"Dampers/Suspension
In the E70, the range of spring/damper units extends from steel springs with conventional dampers through to the new vertical dynamic control (VDC) that, in addition to the electronically controlled dampers, also allows a combination of a 1-axis air spring on the rear axle. This 1-axis air spring is compulsory on vehicles with 8-cylinder engines and/or a
third row of seats."