College of Technology & Computing

### Negative Caster

Negative caster is the forward tilt of the ball joint or king pin from a true vertical, as seen from the side of the wheel. With negative caster the rear part of the pivot point contact providing drag or friction tends to turn the wheel further from the straight ahead position. When both front wheels have negative caster, the vehicle tends to lean in, or bank, on turns. Negative caster reduces steering effort at low speeds. Excessive negative caster causes a front tire and steering wheel shimmy or shake.(many of you have experienced this at the grocery store) Vehicle tends to pull to the side with the least positive (most negative) caster. This usually has to be greater than half a degree.

### Positive Caster

Positive caster is the rearward tilt of the ball joint or king pin from a true vertical, as seen from the side of the wheel. With positive caster the front part of the pivot point contact provides drag or friction and tends to turn the wheel closer to the straight ahead position. When both front wheels have positive caster, the vehicle tends to lean outward, or roll outward, on turns. Positive caster increases steering effort at low speeds. Positive caster assists directional stability by keeping the vehicle on a straight ahead path. Positive caster also helps to return the wheels to a straight ahead position when completing a turn. Vehicles tends to pull to the side with the least positive (most negative) caster. This usually has to be greater than half a degree.

### Neutral Caster

Caster is the forward of rearward tilt of the ball joint of king pin from a true vertical, as seen from the side of the front wheel. Neutral caster does not have a forward or rearward tilt from true vertical. This causes a wander condition of the vehicle. Caster also helps the steering wheel to return to center after a turn. Caster angle has only a minimal effect on tire wear. It also controls steering effort. Cross caster difference from right side to left side will cause a pull to the side with the least positive caster.

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