Steerring Effect

Vehicles with power steering often have more positive caster than vehicles with manual steering. The positive caster helps to overcome the tendency of power steering to hold the front wheels in a turn. The additional positive caster requires greater steering effort. However, the driver does not notice because of the power assist. Positive caster tends to make the wheels toe in and negative caster tends to make the wheels toe out. Therefore excessive positive caster may cause increased steering effort, steering wheel snap-back after a turn, low speed shimmy.