i need to very simple tutorial or example for understanding car physic. i was found “RaceDemo” but its very complicated and not understandable for me. Anybody can give me very tutorial ?
Well, the problem here is that getting vehicle physics right is far from “very simple”, and may require in-depth physics knowlegde. If you want to get into the matter, this presentation from Unite '07 may provide some good insight:
http://unity3d.com/support/resources/unite-presentations/physics-the-right-way
Also, you may possibly want to have a look at this old example code. Not physically correct at all, just a quick attempt to make a car which plays and feels ok.