Wheel reference poses in vehicle


I dont know how to set the wheel reference poses (red circle, or what else is represented by that?) which is not in the center of my wheels, the problem is when you have different wheel radius (like a tractor for instance) it messes up with the balance and the wheels sink into the ground when in play mode.

I found out that you can lock the constraints in rigidbody which fixed most of the vertical offset, but I still have strange offsets I cannot explain.
If someone could provide a sample which goes a bit more into the details than the documentation which is really basic would be much appreciated.