Car Guys/Mechanics: what the heck happened?

[kaisersozei]

Driving home yesterday, I hear a loud screeching/thudding coming from the right side of my car. I thought it was the engine of this old klunker I was passing, but the noise continued once I got by him, so I pulled onto the shoulder. As I slowed down, the noise turned into more of a rhythmic thumping, like I had a flat tire, but the car was not wobbling at all.

Got out, looked in the wheel well, and could see some damage on the inside tread of the front right tire. Changed it out and this is what I found:







Any idea what could have caused this? Something with the strut, maybe, rubbing onto the inside of the tire? Tread separation from faulty tires? Just a routine blowout? There appeared to be enough clearance between the tire and the strut, and nothing interfered with the spare when I replaced it.

These are low profile radials, less than a year old with maybe 20k miles on them. Unfortunately, they're directional tires and not cheap, so I'll probably be forking over some big $$ this weekend to get two replaced. Wondering if it was related to any kind of mechanical failure or just poor construction.