Noted as the first mass-market car with an aluminium chassis, all A8 models have used this construction method co-developed with Alcoa and marketed as the Audi Space Frame.
The difference between axle drum inboard and axle drum outboard is the different location of the brake drum. If the hub is placed out of the brake drum, it is called drum inboard axle.If the hub is placed inside the brake drum, it is called drum outboard