Wheel Alignment Parameters

Wheel alignment parameters are the angles and geometric relationships of the wheels and steering system that ensure proper handling, stability, tyre life and steering performance.

1. Camber Angle

Definition

Camber is the angle between the wheel centre plane and the vertical, when viewed from the front of the vehicle.

Types

• Positive camber → Top of wheel tilts outward.

• Negative camber → Top of wheel tilts inward.

• Zero camber → Wheel is vertical.

Merits

• Proper tyre contact with road

• Improves cornering stability

• Reduces uneven tyre wear when correctly set

Demerits of Excessive Camber

• Uneven tyre wear

• Reduced tyre contact area

• Poor straight-line stability

• Increased rolling resistance

Key point:
Camber → Front view → Wheel tilt → Tyre contact & wear

2. Caster Angle

Definition

Caster is the angle between the steering axis and the vertical, when viewed from the side of the vehicle.

Types

• Positive caster → Steering axis tilts rearward at the top.

• Negative caster → Steering axis tilts forward at the top.

Merits of Positive Caster

• Better straight-line stability

• Provides self-centering of steering

• Improves steering returnability

• Better high-speed stability

Demerits of Excessive Caster

• Higher steering effort

• Increased steering wheel kickback

• Uneven steering effort if left/right caster differs

Key point:
Caster → Side view → Steering stability → Self-centering

3. Toe

Definition

Toe is the difference in distance between the front and rear edges of the two wheels of an axle, when viewed from the top.

Types

• Toe-in → Front edges of wheels are closer.

• Toe-out → Front edges are farther apart.

Merits of Correct Toe

• Improves straight-line stability

• Reduces tyre wear

• Provides proper steering response

• Compensates for small changes during vehicle motion

Demerits of Incorrect Toe

• Rapid tyre wear

• Increased rolling resistance

• Vehicle pulling or wandering

• Poor steering response

Key point:
Toe → Top view → Wheel alignment → Straight running & tyre wear

4. Kingpin Inclination (KPI)

Definition

Kingpin inclination is the angle between the steering/kingpin axis and the vertical, when viewed from the front.

Merits

• Reduces steering effort

• Provides self-centering

• Reduces steering kickback

• Helps maintain directional stability

• Reduces scrub radius

Demerits of Excessive KPI

• Increased tyre wear

• Increased steering effort

• Can affect steering geometry

• May produce undesirable steering behaviour