BMW won't recommend anything other than their set up, why would they? So they will say RFT and * rated in the sizes they delivered the car on.
Running a 245 section on the rear rim will give a stretch to the tyre and probably not sensible either.
Xdrive can give issues when you change the rolling radius so watch out for that if you change to another tyre, tyres that have the same sizes can have a different shape and width so they are not all equal just based on the raw sizing data.
Plenty of people ditch the run flats on x-drive with zero issues but you're not going to get BMW to recommend it.
It's a case of DYOR.
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730d/Z4C
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