There's a D3 owner in Melb with 265/70 MTRs on X5 rims who reports no problems with the tyre/rim combination.
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Its all changed for me now that the D4 has larger brakes. From a good picture of a front wheel that clearly shows the disc and calliper, I've calculated by screen measurements that rim clearance over the disc will need to be 415-420mm and my X5 rims are 400mm so they're not going to fit.