Viper days you can run ANY reasonable/legal tire, as long as your not competing for prize money. I used to run Pirelli's and Tom Sessions knew it, and said no problem. I mean lets not be stupid, and think ET Streets and skinnies would make it on the track, or BFG's but anything thats a good street tire, or road course tire/autocross, I think is more then welcome. Last I remember, I have to PAY to race at viper days. Cant see how they can FORCE me to run a particular brand, when I have to pay to play.
So since Tom is my personal Viper Tech, AND Viper Tech for Viper Days. I think I'll take his word for it.
Feel free to spam me.
Jon