I thought it would be interesting to have a thread about physics engines and tire models of various racing sims. If you have some information or thoughts about these things, you can post them here, or if you know good web pages about this, you can post them too. I have been playing rFactor 2, game stock car extreme and assetto corsa recently, so i am especially interested about differences between those, but discussion about any sims would be appreciated. Also information about how things are done for different sims would be nice. For examble that is test drivers who have driven the real thing used for getting feedback?