Suspension geometry — the complete picture of all wheel angles and positions — is fundamental to how a car handles, steers, accelerates and brakes. Understanding geometry is valuable for anyone modifying a car's suspension, preparing for track days or simply trying to understand why their tyres are wearing unevenly. In 2026, this guide covers the complete suspension geometry picture.

Front Suspension Geometry

Camber Angle

Camber is the vertical inclination of the wheel — the angle between the wheel's centreline and the vertical, viewed from the front of the car. Most road cars have slightly negative camber on the front wheels — the tops lean slightly inward — to improve cornering grip when the body rolls. Typical road car camber: -0.5 to -1.5 degrees.

Caster Angle

Caster is the fore-and-aft angle of the steering axis — the line through the upper and lower ball joints or the strut top mount and lower wishbone mount. Positive caster — where the steering axis is inclined backward — creates the self-centring effect of the steering. More caster improves straight-line stability. Typical road car caster: 2 to 6 degrees positive.

Steering Axis Inclination (SAI)

Steering Axis Inclination is the angle between the true vertical and the steering axis line — combining camber and caster angles. SAI primarily affects steering weight — a steeper SAI makes the steering heavier but improves straight-line stability.

Toe Angle

Toe angle on the front wheels determines straight-line stability and tyre scrub. Slight toe-in — wheels pointing slightly inward at the front — is the most common road car setting, providing stability. Slight toe-out — wheels pointing slightly outward — improves initial steering response but can cause instability at high speeds.

Rear Suspension Geometry

Rear wheel alignment is increasingly important on modern cars with independent rear suspension. Key considerations:

  • Rear camber: Too much negative camber causes inner edge tyre wear. Slight negative camber improves cornering grip
  • Rear toe: Incorrect rear toe causes the car to feel unstable or to drift sideways under braking
  • Thrust angle: The angle of the rear axle relative to the car's centreline — affects straight-line tracking

Performance vs Road Geometry

Street Performance

Performance road cars often benefit from slightly more negative camber than standard — typically -1.5 to -2.5 degrees — to improve cornering grip. However, this increases tyre wear on the straight and requires careful setup to balance grip against tyre longevity.

Track Day Geometry

Track day alignment prioritises grip above all other considerations. Typical track geometry:

  • Front camber: -2.5 to -3.5 degrees
  • Rear camber: -1.5 to -2.5 degrees
  • Reduced or zero toe on both axles
  • Increased caster if adjustable — for improved steering feel and camber gain in corners

Why Geometry Matters for Tyre Life

Incorrect geometry causes specific tyre wear patterns that reveal which angle is wrong:

  • Inner edge wear: Too much negative camber
  • Outer edge wear: Too much positive camber or inadequate camber
  • Feathering: Incorrect toe
  • Patch wear: Incorrect toe combined with other issues

Correcting the geometry saves tyre costs that can quickly exceed the alignment cost many times over.

Geometry and Suspension Modifications

When modifying a car's suspension — fitting lowering springs, coilovers or new suspension components — the geometry must be checked and corrected:

  • Lowering a car changes the camber angle on most suspension designs
  • New springs may require different spring perch positions to achieve correct ride height
  • New dampers may affect geometry if they are a different length than the originals
  • Aftermarket control arms and wishbones may require geometry adjustment to fit correctly