For this, we would suggest you walk into the nearest authorized service centre as they will be the better people to assist you. You can click on the following link to see the details of the nearest service centre and selecting your city accordingly - Service centre.
The BMW 7 Series ground clearance is 152mm. For these tyres recommended tyre pressure is between 30-35 PSI. 35 PSI will give you better fuel economy while 30 PSI can be used for a smoother and more comfortable ride.