Last week I was flushing the brake fluid to get ready for an upcoming HPDE event. I leaned on the spare tire but only heard *hssss* as I didn't exactly stop as I should have. Huh. Break out the air compressor to try to figure out why it's so, well, flat.
Wouldn't take any air? What the hell? Upon investigation I found that the entire valve stem was split near the base. No wonder. I took it by a tire shop to plead for a stem replacement. No dice as the tire is "over 10 years old". No crap, it's the original unused spare. Didn't offer me any suggestions, so I left, dejected.
I ordered a stem replacement kit, figuring I'll swap that out and be good to go. Unfortunately the thoughts in the recesses of my brain-matter coaxed me into buying a new tire enTIREly.
While the original 105/95/17 seems to be unobtanium, there are other sizes available. I see a few people talking about a 115/95/17, which is about 0.7" larger in diameter and may have fitment issues in the trunk.
I found a 125/80/17 from Continental, the sContact. It's effectively the same diameter, and about 0.8" wider overall. I ordered it from Tire Rack on Monday, and had it installed today. It almost looks identical to the original (which had never been mounted on the car). The clearance in the frunk is precariously close, but it fits. Applying the tire cover takes a bit more fiddling as well. Now my Boxster has a spare that isn't about old enough to drink. See for yourselves.