When brake force is applied, if the level of braking is increased to the levels of co-efficient of friction, mu, the wheel can no longer support the force being applied to the rubber, and hence the available stopping force begins to diminish.
Operation at the peak of the mu-slip offers the highest braking efficiency. Research suggests that a skid develops that may lock the wheel and blow the tire if unchecked.
Modern anti-skid brake control systems measure the speed of the wheel to find slip and developing a correction signal. The control unit finds out where the tire is operating on the mu-slip curve and sends a correction signal to the antiskid valve to reduce applied brake pressure. This helps the vehicle to avoid skidding.