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Caster

Car culture term

What is Caster?

The rearward or forward tilt of the steering axis when viewed from the side of the vehicle, affecting straight-line stability, steering return-to-center, and high-speed handling.

Caster is one of the three primary wheel alignment angles, alongside camber and toe. It describes the tilt of the steering axis (the line through the upper and lower ball joints or strut axis) when viewed from the side. Positive caster means the steering axis tilts backward at the top (the contact patch trails behind the steering pivot point), which is the standard setup for virtually all modern vehicles. Negative caster tilts forward at the top and is rarely desirable.

Positive caster creates a self-centering effect because the tire contact patch trails the steering pivot, creating a mechanical tendency to return to straight-ahead. More positive caster increases straight-line stability and return-to-center feel, which is why performance and track cars often run more caster than the factory baseline. The trade-off is increased steering effort (more caster makes steering heavier).

Caster is not adjustable on most stock vehicles. Lowering a car can alter effective caster depending on suspension geometry. Aftermarket upper control arms or strut mounts on some platforms allow caster adjustment. Track-day and autocross competitors often maximize caster within the available range for stability and feel benefits. Caster imbalance between left and right wheels causes the car to pull to one side.

Related terms

CamberToe AlignmentCoiloversWeight transferOversteerUndersteer

Frequently asked questions

What is the difference between caster, camber, and toe?
All three are alignment angles. Camber is the inward or outward tilt of the wheel when viewed from the front. Toe is the direction the wheels point (inward or outward) when viewed from above. Caster is the tilt of the steering axis when viewed from the side. All three affect handling and tire wear.
Is more caster always better?
Not necessarily. More positive caster improves stability and return-to-center, but also increases steering effort. On power steering cars, this is largely masked. On manual steering cars, high caster can make steering quite heavy. Most performance setups run as much caster as the geometry allows while maintaining acceptable steering effort.
Can caster affect tire wear?
Directly, less than camber or toe. However, caster imbalance (different caster left vs right) causes pulling and uneven wear across the axle. A vehicle that pulls to one side often has a caster or camber asymmetry. Even caster across both front wheels is important for neutral handling.
Does lowering a car affect caster?
It can, depending on the suspension design. Strut-based front suspensions often see caster change as the strut angle changes with ride height. Wishbone (double-A-arm) suspensions may have less caster sensitivity to ride height. This is why an alignment check after any suspension height change is essential.
How is caster adjusted?
Most factory suspensions do not have caster adjustment. Aftermarket solutions include adjustable upper control arms, eccentric bolts at certain pivot points, or strut mounts with caster correction built in (common for lowered cars). Alignment shops can measure your current caster; correcting it requires the right hardware for your suspension design.
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