See Figures 1, 2, 3, 4 and 5
Correct alignment of the front suspension is necessary to provide optimum tire life and for proper and safe handling of the vehicle. Caster and camber cannot be set or measured accurately without professional equipment. Toe-in can be adjusted with some degree of success without any special equipment.
Caster is the tilt of the front steering axis either forward or backward away from the vertical. A tilt toward the rear is said to be positive and a forward tilt is negative. Caster is calculated with a special instrument but one can see the caster angle by looking straight down from the top of the upper control arm. You will see that the ball joints are not aligned if the caster angle is more or less than 0 degrees. If the vehicle has positive caster, the lower ball joint would be ahead of the upper ball joint center line. Caster is designed into the four wheel drive front suspension. Small caster adjustments can be made on four wheel drive front axles by the use of tapered shims between the springs and the axle.