Like the guys say Alvin,these caster shims are there to fine tune the geometry.
These affect the KPI (king pin inclination)
Generally if the axle(king pin) is tilted forward at the top in relation to the rest of the truck,the steering would become lighter and more prone to wander,it's self centering ability is reduced.
i.e. If you were to turn a corner and release your grip on the wheel it would continue turning.
Whereas if it were tilted back it would make the steering slightly heavier but much nicer at speed,the centering will be increased.
When I used to work on lowering VW Bugs where the front was radically lower than the back end we would lose caster,so we would add extra shims(upto 6 degrees)for the same reason.
Last edited by jockbolter50; 04/01/2012 9:33 AM.
