Car not turning on plane.

I've made a car, although not with wheel colliders cos i don't have a clue how to script for them, so it's just using addForce and AddTorque, it drives perfectly on a terrain, but put it on top of a plane or cube, and it won't turn, only drive in a straight line. How do I fix this and/or how do I make a really cimple script for a car that will allow turning and straight line movement using WheelCollliders In unity?

If you're making any sort of vehicle, not using a Wheel Collider is a dumb move, especially if your only reason is "because I don't know how to script for it". There are quite a few examples out there of using Wheel Colliders with Unity, have you searched the forums, Google, and the Unify Community Wiki?

And most important of all, read the Wheel Collider Documentation, which outlines all the functions and how you use them (there's even example code in there).

If you use a Wheel Collider, turning your car is really easy (using steerAngle).