What are you going on about? Doesn't matter which tires you choose in the game, you will always get a faster time than real life. It's like you all of a sudden have an issue with GT5 not being like for like perfect replication of real life. Just looking for an argument or what?
Case end point, lack of fear in a game allows us to push virtual cars well beyond the limits any of us ever would outside of your consoles, stop acting like you didn't know this. It's like every where you look on here it's "oh look, GT5 isn't perfect, let me tell everyone who I can". No matter how close they can replicate anything in the game, you will never ever replicate realistic lap times considering you have no fear at all, no matter how fast you drive in the game you won't care.
Anyway, PD can laser scan all their courses into the game, and get the best tire simulation they can, balance the physics immaculately and precisely and you will still get faster lap times in the game than anyone in real life can. I don't care about matching anything as long as the game can realistically give me something fun to do, especially considering I can't yet go to many of these courses and drive my car around them.