This would be for a spare. I have a car on order and have been looking into spare options...originally I was thinking a temporary spare but don't want to be limited in speed and range if it takes a week or so before i have a chance to repair/replace a tire. The temp one from BMW X3 F25 Spare Tire Kit (Emergency Space Saver) : Bimmerzone.com that I've seen recommended actually seems to be an 18-incher. Yet in a chat with tirerack.com they say that an 18" wheel won't work with the MS...it won't clear the caliper. Is that correct or not? I'd like to pick an 18 if it is workable because there can be a slight weight and space savings (I can pick something a bit skinnier than OEM).