Apex

The apex is the point in a corner where a driver's chosen line comes closest to the inside edge of the road or track. Racing line theory generally holds that the fastest way through a corner involves using the full width of the track, starting from the outside edge on entry, brushing the inside edge at the apex, and drifting back out to the outside edge on exit, a path that straightens the effective radius of the turn and allows a higher sustained cornering speed than simply following the geometric centerline of the road.

Not every apex is in the geometric middle of a corner. Drivers and instructors distinguish between an early apex, where the car touches the inside edge before the corner's midpoint, and a late apex, where that contact point is delayed until after the midpoint. A late apex is generally favored on corners leading onto a straight, since it allows the driver to get back on the throttle sooner and carry more speed onto the following straight, while an early apex can be useful on a corner that tightens further partway through, sometimes called a decreasing-radius turn.

Choosing the correct apex for a given corner depends on what follows it: the geometry of the corner itself, whether it connects to a straight or another corner, and the car's specific handling characteristics all influence where the ideal apex point falls. Missing the apex, either by turning in too early and apexing early on a corner that calls for a late apex, or by running wide and missing the inside edge entirely, is one of the most common technical errors in performance and track driving, and correcting apex placement is a core focus of most driver coaching and track day instruction.