WARNING: This page is about a different car, the 2012 BMW 328xi, 2011 BMW 328xi, 2010 BMW 328xi, and 2009 BMW 328xi. However, it is still accessible from the selected car via links, so may be relevant.
Is the angle bisector from the total rear-wheel toe.
Front-wheel measurements are taken in reference to this axis.
Symmetrical axis 2
Centre line running through front and rear axles.
Fig 1: Identifying Geometrical Driving Axis And Symmetrical Axis