Loading…
A conceptual model showing that a tire's total available grip is shared between cornering, braking, and acceleration. The combined forces form a roughly circular boundary — you can trade lateral grip for longitudinal grip, but the total is limited.
Segers explains in Analysis Techniques for Racecar Data Acquisition: "A racing tire can develop approximately equal power in acceleration, braking, and cornering. Plotting the maximum forces that a tire can develop in each direction gives the traction circle of the tire." He describes how to read a full-lap plot: "Let's take every single data point for a full lap around a circuit and plot the results in an X-Y chart. An example of such a chart for a lap around the French Nogaro circuit is known as the traction circle." Gillespie's Fundamentals of Vehicle Dynamics adds the tire-level physics: "The general effect on lateral force when braking is applied — as the brake force is applied, the lateral force gradually diminishes due to the additional slip induced in the contact patch." The ideal driver keeps the combined forces near the edge of the circle at all times — any time spent in the center means grip is being left on the table.