And it was the newest one on the car.
So, when I limped on up to Maynard and Lesieur, up in Nashua, NH with three old tires and one donut spare (newly acquired from Holland Used Auto Parts in North Billerica, MA for the princely sum of $10, wheel included) I told them to swap out the two failed tires--the one which had blown, and the one which had had a tread separation on 128 a while back--hand me back the newest of the remaining tires as a full-sized spare, and put four new tires on the car.
Efficient bunch, Maynard and Lesieur. (Thanks for repeating the pointer, frotz.) They had the new tires on and torqued down within 25 minutes of my walking in the door to ask about tires. (And the next day, they retorqued them to make sure everything was tight.)
Boy, does having new tires with actual tread ever make an incredible difference. It's almost like driving a different car. Driving through the downpour we had the last few days was easy with brand-new tires. Hydroplaning rarely happened, and the grip, wet or dry, was impressive. With the old tires, I often used to spin the tires when coming off the line; now I just accelerate cleanly when I let out the clutch, regardless of how hard I push it.
Of course, now I have seven wheels (two donut, five full-sized) and six working tires (five full-sized and one donut) for the car. I wonder what I should do about the extra donut wheel. I imagine should probably just dump the bad donut tire, but that would require removing it from the donut wheel.