Caster

Caster is the tilting of the front steering axis either forward or rearward from the (1) vertical. It is measured in degrees. A rearward tilt is positive and a forward tilt is negative. On the short and long arm type suspension you cannot see a caster angle without a special instrument. However if you look straight down from the top of the upper control arm to the ground, the ball joints do not line up (fore and aft) when a caster angle other than 0 degrees is present. With a positive angle, the lower ball joint would be slightly ahead (toward the front of the vehicle) of the upper ball joint center line.

Incorrect caster may result from damaged control arms and other related front suspension parts.