Threshold braking
Encyclopedia
Threshold braking or limit braking is a driving
Driving
Driving is the controlled operation and movement of a land vehicle, such as a car, truck or bus.Although direct operation of a bicycle and a mounted animal are commonly referred to as riding, such operators are legally considered drivers and are required to obey the rules of the road...

 technique most commonly used in motor racing, but also practiced in road vehicles to slow a vehicle at the optimum rate using the brakes.
The technique involves the driver controlling the brake pedal (or lever) pressure to maximize the braking force developed by the tires. The optimal amount of braking force is developed at the point when the wheel just begins to slip
Slip (vehicle dynamics)
In vehicle dynamics, slip is the relative motion between a tire and the road surface it is moving on. This slip can be generated either by the tire's rotational speed being greater or less than the free-rolling speed , or by the tire's plane of rotation being at an angle to its direction of...

.

Kinetic and static friction

Braking beyond the slipping point causes the tire to slide and the friction
Friction
Friction is the force resisting the relative motion of solid surfaces, fluid layers, and/or material elements sliding against each other. There are several types of friction:...

 adhesion between the tire and driving surface is reduced. The aim of threshold braking is to keep the amount of tire slip at the optimal amount, the value that produces the maximum frictional, and thus braking force. When wheels are slipping significantly (kinetic friction), the amount of friction available for braking is typically substantially less than when the wheels are not slipping (static friction), thereby reducing the braking force. Peak friction occurs between the static and dynamic endpoints, and this is the point that threshold braking tries to maintain.

Other factors

Because available friction at a given moment depends on many factors including road surface material, temperature, tire rubber compound and wear, threshold braking is nearly impossible to consistently achieve during normal driving.
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