Self centering

[MikeB]

Originally Posted by alga

One is as good as the other:



Fixing the Sierra's trail inceases positive caster distance, too. It's the distance between the kingpin axis' projection intersection with ground and the centre of the contact patch, and it is precisely the lever that does self-centering.

Just to clarify,
When you move the inserts, it doesn't change the castor angle as the top and bottom pivots are fixed, it effectively moves the centre line of the wheel forward and backwards changing the trail, so in the diagram above the steering axis stays fixed the wheel effectively moves for and aft.

From recollection the only thing that would give you any self centering when stationary is king pin inclination as this causes the body to rise and fall when the wheels are turned so the vehicle mass forces it back down due to gravity. (sorry missed someone already said this!)