I drive my 818 a lot (including yesterday to the office, without windows, with morning temps at 15 degrees).

There's no room for a spare tire, so I was thinking of putting on run flats for everyday use (right now, i keep a can of fix-a-flat with me), and swapping to something sportier when I go autocrossing.

However, I have never had run flats on any vehicle, so I thought I'd check to see if anyone here had recommendations. I imagine ride harshness will increase, but that doesn't bother me much. Performance would likely suffer too, but I'm looking for something for around town and to the office sort of stuff, so driving will be pretty tame.