Racing game troubles

Hi, I have started working on a racing game and I am having a few problems. The first is that once the car starts to drive the shocks rase it up quite high, would that be an animation or a coding thing, second is that the car flips VERY easily, I believe it is because the shocks make once side of the car extreamly low and the other high.

here is the file I have started with the vehicle in it so you can see for you're self what is happening, I know it doesn't have a texture with it (the car) that is because I have to re-do it lol.
FILE HERE