Heading away from my house, I noticed my bike was bouncing up and down, and discovered a big bulge in my rear tire. So I put it back in the garage, and took the other bike.

Upon un-mounting the tire, I discovered that the cords on the inside of the tire were badly frayed, over roughly an inch. On the outside, plenty of rubber left, but two large punctures on either end of where it was frayed. The punctures look like a vampire bite from an old horror movie. The tire was still holding pressure -- it has a MrTuffy liner.

The tire is a Cheng Shin C637, and fortunately I had a new one to install right away. It's a cheap tire, but I've gotten good lifetime out of them with the liner -- this one is probably four or five years old, ridden for daily commuting, about 8 miles round trip.

I'm curious as to what caused this. Maybe something went through the tire but not the liner, wandered around inside while fraying the cords, and then bored its way back out, like some little stone.

The picture is of the inside of the tire, splayed open with a spring clamp in my workshop.