Tyres.co.uk has Pirelli P Zero (PZ4) Run Flat and Bridgestone Alenza 001 for BMW X6 factory 20-inch staggered RSC fitment: 275/45 R20 110Y XL front and 305/40 R20 112Y XL rear. Make sure your registration matches the XL load rating and run-flat requirement.
Your BMW X6's tyre pressure and size placard is located on the driver's door aperture, at the B pillar. It has the approved factory wheels and tyres for your BMW X6 along with the recommended inflation pressures. This placard is your best source for BMW X6 tyre size. You can use the sidewall for a cross reference, but you must confirm with the placard and manual.
Not all tyres need to be replaced on the BMW X6. The other axle can be serviceable and a pair can be replaced. For the BMW X6 xDrive, all four tyres must be of the same brand and design with the same level of tread; if this cannot be achieved, all four must be replaced. Per the UK safety guidance, when fitting two tyres, the new tyres must be installed on the rear axle.
