WARNING: This page is about a different car, the 2018 BMW X5, 2017 BMW X5, 2016 BMW X5, 2015 BMW X5, and 2014 BMW X5. However, it is still accessible from the selected car via links, so may be relevant.
Determine actual ride height (A) - to do so, attach tape measure to rim flange (2) at bottom middle and measure to wheel arch lower edge (1).