From noodling around in the Search Tab, it appears that the X6 wheel hub bore sizes are different from the E70, in rear:
X5 E70
center bore is 74mm on all wheels.
The X6 front
wheel center
bore is 74mm but
rear wheel is 72.5mm(which is E53 X5
bore size), and thus, would need to be machined to the 74 mm size, to fit the E70, imo.
To make the situ more confusing, there is another post in the thread I ref'd suggesting that the X6 front hub is smaller...
Take a read of the pasted thread, and proceed carefully, or measure the X6 wheel hubs, if possible.
http://www.xoutpost.com/bmw-sav-foru...ets-x6-x5.html
GL, mD