🔧 Caster
The backward tilt of the steering axis. More caster = more stability and on-power steering; less = more aggressive off-power steering.
What it actually does
Caster is the backwards tilt of the steering axis viewed from the side of the car — the same geometry that makes a shopping trolley wheel self-centre. It is what makes a car track straight on its own and return to centre after a corner.
In practice
More caster generally gives more straight-line stability and more steering as the car loads up in the middle of a corner, at the cost of some initial turn-in response. Less caster gives sharper, more immediate turn-in but a twitchier car. It is usually adjusted with caster blocks or shims.
Worth knowing
Caster interacts strongly with camber gain as the suspension moves, so change it in single steps and re-check how the car turns in versus how it holds a line.