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.
See Figure 1
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.
See Figure 2
Camber is the slope of the front wheels from the vertical when viewed from the front of the vehicle. When the wheels tilt outward at the top, the camber is positive. When the wheels tilt inward at the top, the camber is negative. The amount of positive and negative camber is measured in degrees from the vertical and the measurement is called camber angle.
See Figure 3
Toe-in is the amount, measured in a fraction of an inch, that the wheels are closer together in front than at the rear. Some vehicles are set with toe-out, that is, the wheels are closer together at the rear, than the front, to prevent excessive toe-in under power.