The revenge of the frickin' van
I should have known that being driven 3,000+ miles in a week, the van would exact some sort of revenge: Its rear driver side tire is dead.
It just wasn't keeping air in itself any more, and I can see why -- riding it underinflated, as I had for a few miles in Georgia, wore it straight through to the steel belts.
So I changed the tire, and discovered in the process that the spare, while full-sized, is on a cheap rim that's rusted straight through. The rim's been strapped to the underside of the van for a decade now, so I shouldn't be surprised. Still, the convenience of not having to deal with a donut is useless if the rim the spare is riding on is garbage.
A day on that rusted rim and the lug nuts loosened up, unfortunately - now the tire is wobbly and I can't get the lug nuts tightened down enough. I'll have to get it replaced tomorrow, and I pray I can drive the van to the mechanic's without f'ing something up further.