I don’t recall suggesting 315’s… I do remember mentioning a first hand experience with both the tires to help make a decision though. I’m sorry if my story involved a different car with different tire sizes, but it was still comparing the tires to one and another.
The et street bias ply’s are dot legal… I wouldn’t suggest driving to the track with them though. IMHO they are just for people who want to stay on the street class but want to run a really sticky tire. If you are running these tires on the track only, I would stay with the slicks. Why run a less sticky tire?