Caster Angle

          A caster is the angle between an imaginary line drawn through the upper and lower steering pivots (viewed from the side of the vehicle). If the top of the line tilts rearward, the vehicle is said to have a “POSITIVE” caster. If the top of the line tilts forward, the vehicle is said to have a “NEGATIVE” caster. The positive caster can also be defined as when the spindle is tipped so that the pivot support centerline the road surface of the initial tire contact. The negative caster would then be the center line intersection to the road surface tire contact.

         Most vehicles produced today do not have adjustable caster angles. Many early-model vehicles have adjustable casters (along with camber). By setting the caster angle on the driver’s side a particular (half) degree less than the passenger side for positive caster specifications or half a degree more for negative caster specifications.