Caster refers to the rearward tilt of the steering axis (kingpin) when viewed from the side of the kart, creating a fundamental aspect of steering geometry that significantly influences front-end grip, steering feel, and the kart's ability to lift the inside rear wheel through corners.
Caster adjustment effects:
- Increased caster: Provides more front grip, heavier steering feel, improved chassis lift, but requires more driver effort
- Decreased caster: Lighter steering, less front grip, reduced jacking effect, easier for younger or less experienced drivers
- Typical range: 0-6 degrees depending on class regulations and driver preference
The caster angle is adjusted using eccentric washers or shims on the kingpin mounting points. Greater caster creates a mechanical advantage that helps lift the inside rear wheel during cornering (the jacking effect), which is essential for proper kart rotation. However, too much caster can make the steering physically demanding and cause excessive front tyre wear. The optimal setting balances grip, steering effort, and chassis dynamics to suit the driver's strength, experience level, and track characteristics.