I've used the concept of a 3D traction/friction circle to help drivers realize that 'the limit' is not a cliff that they will fall off of if they make a tiny error when exploring the limit; it's just an optimum point on a much larger continuum of tire performance ranging from almost no drift angle to scrubbing the tire sideways across the track.
The 3D traction circle (and it's relationship to the traditional 2D traction circle) are explained on pages 18-25 in this
document.