Wheel Alignment Terminology — Positive Caster In steering geometry, caster is called positive when the top of the steering axis (kingpin or virtual kingpin line) is inclined toward which direction?

Introduction / Context:
Caster is one of the primary wheel alignment angles (along with camber and toe). Understanding positive versus negative caster is essential for diagnosing steering return, straight-line stability, and steering effort characteristics.

Given Data / Assumptions:

• Front-wheel steering with a defined steering axis (kingpin or steering knuckle pivot line).
• Vehicle stationary reference axes: front–rear and left–right.
• Small angles typical of road vehicles (a few degrees).

Concept / Approach:
Positive caster means the steering axis tilts rearward at the top (like a shopping cart caster trailing behind its pivot). This geometry promotes self-centering and directional stability because the contact patch trails the steering axis projection on the ground, generating a restoring moment when the wheels are turned.

Step-by-Step Solution:
Visualize the steering axis in side view.Tilt direction check: top toward rear → positive caster.Therefore, select “rear of the vehicle”.

Verification / Alternative check:
Most modern cars use positive caster to enhance straight-line stability; specifications list positive degrees of caster.

Why Other Options Are Wrong:
Front of the vehicle: defines negative caster.Left/right: describes camber/toe asymmetry or SAI differences, not caster direction.Vertical: zero caster, offering little self-centering.

Common Pitfalls:
Confusing caster with camber (front view tilt of the wheel).

Final Answer:
rear of the vehicle