When lifting the front of a Super Duty 2.5″, caster will be reduced by 1°. The 2° shim specified with our 2.5″ lift systems not only restores caster but increases it by 1° from the stock spec to ensure proper tracking with larger tires.
Our 4.5″ lift systems drop the radius arm pivot point 4.5″ to match the lift; thus, caster is maintained. We include the 1° shim to increase caster 1° over stock for the abovementioned purpose.
If running Carli Radius arms, it’s not necessary to run any additional caster correction as they increase caster 1°.