Slip Angle
The angular difference between the actual direction of travel of a tire and the direction the wheel is pointing.
A slip angle is the angular difference between the direction in which a wheel is pointing and the actual direction of travel of the tire's contact patch. Slip angle is a critical concept in tire dynamics and vehicle handling, explaining how pneumatic tires generate lateral (cornering) force.
As a vehicle corners, lateral force pushes against the tire, causing the rubber tread elements in the contact patch to distort and twist relative to the wheel rim. The tire does not slide; instead, it rolls at a slight angle to the direction the wheel is steered. Cornering force increases proportionally with the slip angle up to a certain limit; if the slip angle becomes too large, the tire loses traction and begins to slide.
If a vehicle has worn suspension bushings or incorrect wheel alignment (especially toe), the tires can run at excessive slip angles even when driving straight. This increases rolling resistance, wastes fuel, and causes rapid tire tread wear. Alignment technicians use slip angle concepts to optimize alignment settings for racing or daily driving stability.