Kevin, you make some good
Kevin, you make some good points and I appreciate you expanding on the story. BMW has done its best to make people think its run-flats (really the tire makers' run flats) are safer on the highway in some failure situations. Believe what you like. On its fastest cars (M series) BMW does NOT use run-flats. - With regard to your spare scenario, a run flat would have failed at 50 miles, rather than the 300 you point to according to BMW and the tire information. So I don't get the point. - If you ever do decide to try run-flats on a car that was not designed for them, read up first. The damper (shock absorber) and spring rates on a car design for run flats is not the same as cars that are designed for conventional modern tires. You seem to be all about safety, so you may want to be aware of that. - - Finally, BMW's newest model, the i3, does not use run-flats and has no spare. The tires are also a size only it uses. I have no clue how that makes sense in a world where people like me and you plan carefully ahead for things like punctures and highway damage at high speed, or for being safe in places we don't want to be stranded with a puncture. So my way of seeing this is that in BMW's newest model your wife would not be protected in either scenario one or two, and in scenario 3 and 4 you would have to wait three times for a tow and then skip your road trip.