Before I start, I apologise, as a Brit, for not already finding the answer to my query......
Tell me. Can you exchange 18"+ wheels between the E53 and E70 X5s. (I have one of each)
I already realise that you must not use run flat tyres (tires to you) on the E53 if it hasn't got tyre (tire) pressure monitoring. (Mine has as it's UK supplied '06.)
Regards to you all
John