@rene4406 posted:The Bump steer depends on several parameters, the main ones, far ahead of all the others, are the position of the steering rack, in height and lengthwise, and on the position of the articulation point of the steering rods which must be located in the shot of the four triangle joints on the frame. What is true on one car, your '65 Shelby GT 350 for example, is therefore not necessarily true on another.
It is generally possible to reduce the bump steer by adjusting the position of the steering rack with shims.
I am aware that there are differences. I used the 65 GT350 only as an example of owners not even knowing that they had it or what it is.
What are your measured bump steer changes before the castor changes and after?
All cars are going to have some since the joint center lines move in arcs, not strait lines. You can only retain what exists, increase the change or reduce the change.
Bump steer is going to occur with toe changes due to suspension moves up and down.