What does castor DO ? ?
Everybody says use more castor to make it go straight, not wander, and set toe out on a T bucket with a front drag link. King pin inclination. or the center line thru the ball joints also is a major factor in suspension design but is not adjustable so is not discussed.
Suspension 101 Bend some stiff wire making a T. then with one leg pointing out like a spindle stub and the top of the T verticle like the king pin. Now rotate the king pin to simulate turning left and right. The end of the spindle (wheel) stays the same distance from the ground. Large construction, and some semi tractors use 0 or very little king pin angle to have easy steering. Now tilt your king pin adding some castor, Then when you turn your steering you will see that when you turn one direction the "wheel" tries to move down raising the chassis. then when you turn the other direction the "wheel" will raise lowering the chassis, This alternate raising and lowering can create an osillation or death wobble. Shocks can dampen out the bad design.
Now bend the wire to create some king pin angle and start with 0 castor . Now when you turn either direction the "wheel" moves down raising the chassis, the vehicle weight will bring the steering back to neutral straight ahead. Now adding a little bit of castor will increase the lift in one direction and decreasing the lift in the other direction but Not causing a drop. Then you can add more castor to the point where you get a lot of lift in one direction and Drop on the other side of the chassis. A suspension with a lot of king pin angle does not require as much castor for stability
.Front tie rod normally do not take any slack out of the linkage to create more toe out but compress and actually move the wheels to 0 or a little toe in in actual travel.