Animation - Car following track and wheel rotation, where to find how to tutorial

I need to animate a car and I want to make the Wheels rotate when I drag the car forward.
I have manage to solve how to do this with a curve and while one Wheel is following that curve the Wheel rotate.
But now I want too have 4 Wheels and since the front Wheels will rotate att a different speed when you make a turn, does anyone know how to solve that?
Example on animation that I also want to do, see this Youtube clip:


Hey; Check out DanPro 's Vehicle rigging tut on youtube (link below) Not sure if he explains how to get the wheels to turn at different rates - that is a bit involved, post back if you need more help…