[![enter image description here][1]][1]

*Figure 1. The castor point is the intersection of the pivot axis with the floor.*

[![enter image description here][2]][2]

*Figure 2. For travel to the right we have three situations: (a) No castor action. (b) Correct castor action as the castor point is ahead of the point of contact of the wheel. (c) Reverse castor action which will be problematic in service.*

What matters is where the axis of steering hits the road. For castor action that needs to be ahead of the point of contact between the wheel and the road.


  [1]: https://i.sstatic.net/I1VYTm.jpg
  [2]: https://i.sstatic.net/XuPJZ.png