During a Seat Time event at Summit Point I noticed a vibration during my 3rd session. It got so bad I cut my session short. After inspecting each tire I found the driver's rear to have a bulge in the tread pattern. only one section of the tread was deformed, the rest of the tire was fine. I guess that's what I get for running cheap street tires on the track.

Ryan

http://f3.yahoofs.com/users/41e733cazc4b75088/6862/__sr_/7839re2.jpg?ph4KPdEBV4CUreot

http://f3.yahoofs.com/users/41e733cazc4b75088/6862/__sr_/8d70re2.jpg?ph4KPdEBTMgMrkGL

What tire/brand and how old were they?

Sumitomo HTR Z ll

They are about 4 years old.

I bet the age significantly contributed to its failure.