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A steering geometry where the inner wheel turns at a greater angle than the outer wheel during cornering, matching the different turning radii of each wheel. The amount of Ackermann effect is a setup variable that affects tire wear and cornering behavior.
Jazar's Vehicle Dynamics Theory and Application explains the speed dependency: "The inner wheel of a vehicle in a high speed turn must operate at a lower steer angle than kinematic steering. Reducing the steer angle of the inner wheel reduces the difference between steer angles of the inner and outer wheels. For race cars, it is common to use parallel or reverse steering." Seward's Race Car Design adds the practical observation: "There is very little difference between the inner and outer wheels at up to 5 degrees of steering angle." At low speeds and large steering angles (like autocross or tight hairpins), full Ackermann reduces tire scrub. At high speeds with small steering angles (like fast sweepers), parallel or anti-Ackermann is preferred because the heavily loaded outer tire benefits from a larger slip angle than the lightly loaded inner tire — a direct consequence of tire load sensitivity.