Car Guys/Mechanics: what the heck happened?

[Bax]

Yep, bad alignment wore out the rubber casing near the edge then the radial plies took care of the rest. There is a lot of force from the steel belts pushing upwards to help stablize the tire. Once the rubber is gone and you eat into the nylon wrap it just pops up. You can tell from the scalloped edges on the other side of the tire that you have alignment issues.

New tires then aligment should fix the problem as long as there's nothing else wrong in your stearing.

Also, Sumitomo tires aren't known for their quality. Try looking into Yokohama for some well priced replacements. (Tirerack.com) has the best prices but you get nailed on the install.