>>is simply a follower of the forces Yes, but on a car, that amounts to being a self-centreing action. To see this, probably the best way is to draw out the force vectors acting at the contact patch. In a car (not a bike), whether you choose to implement trail by moving the "king-pin" axis forward, or tilting it, as long as the projection of the swivel axis is ahead of the contact patch, you get self-centreing action.