When I went out to run errands yesterday, I glanced at the Zed Drei's left rear tire in the garage and thought "Hmmm... That looks a couple pounds low. I'll hit it with the compressor when I get back."
I went through the drive-through at the bank, crossed the street to Target, and when I emerged from Target with my paper towels and whatnot, I glanced at the Zed Drei's left rear tire in the parking lot and thought "Golly gosh gee whillikers, that beloved tire is flat as gosh darn it all."
Luckily, right across the street, over near the bank, was the Midas from which I had purchased the very tire in question. I limped over and was informed that they wouldn't be able to get my car on a lift for an hour or so, so they filled the tire with air and I took my shopping home and off-loaded it to return at the appointed time...
...whereupon the problem was discovered to be, not the tire at all, but a crack in the by-gawd wheel rim. So, now I am faced with the choice of purchasing a new wheel from BMW, which will no doubt be priced like imported sin, trying to find a used rim (none of the guy at Midas's sources had one) or attempting to see if there are any places that can repair the crack.