Generally, there are two kinds of resistance in the car during braking: one kind of resistance is the frictional resistance generated between the brake friction plate and the brake drum or brake disc.This resistance is called the resistance of the brake system, because it provides The braking force during braking is also called the braking force of the braking system; another type of resistance is the frictional resistance generated between the tire and the road surface, also known as the ground braking force. The limit value of the ground-to-tire tangential reaction force is called the tire-road adhesion force, and the magnitude is equal to the product of the ground-to-tire normal reaction force and the tire-road adhesion coefficient. If the braking force of the braking system is less than the tire-road adhesion, the car will maintain a stable state when braking. On the contrary, if the braking force of the braking system is greater than the tire-road adhesion, the car will lock and slip. shift.The ground braking force is restricted by the ground adhesion coefficient. When the braking force of the braking system generated by the brake increases to a certain value (greater than the adhesion), the car tire will slip on the ground. The difference between the actual speed of the car and the circumferential speed at which the wheel rolls is called the slip rate of the wheel.The definition of the slip rate S is