Originally Posted by watchhok
Runflat is fine by me, but all I want is that I could use the 388 for summerwheels and the 436 for winterwheels. But that seems not to be possible without a 3th set of wheels,
the point is not about the runflat.
As I said earlier, the question is whether you want to stick to what you dealer wants or what is technically possible. From a technical point of view, what you want to do is possible without any problem.
However, if you want to please your dealer you buy two additional 436 rim sold for the front (7.5''x18) and use the two others you already have. You will get the 4x7.5''x18 required to please BMW sales department and still use 436 for winter.