Braking Forces

When the brakes are applied, brake force counters the inertia of the moving vehicle. This force is created by the brake pads acting on the rotors and through the wheel and tire to the roadway. Even in the best of conditions, some wheel slip occurs. Up to a point this wheel slip is acceptable and in most cases it can even be helpful.

When braking, the transmitted brake force concentrates at the tire "foot print", where the rubber meets the road. This causes a distortion which, when excessive, promotes wheel slip.





When controlled, the distortion can actually enhance the transmission of brake force. Therefore, the ABS logic allows wheel slip up to 20-25%. Beyond that the ABS system limits the application of additional brake force. This allows the transmission of maximum brake force while reducing the stopping distance.

The transmission of braking forces and the retention of Lateral Locating Forces are inverse. That is to say as braking forces increase the locating forces decrease.

As indicated in the chart, the rolling wheel has a wheel slip value of 0% which provides the best Lateral Locating Forces.

As the applied brake force increases the locating force decreases. Depending on the prevailing road surface friction, the optimum transmission of brake force is at the end of the "stable range" with a wheel slip value of 20-25%.

Additional brake force at this point is clearly counter- productive as the additional brake force only increases wheel slip and reduces Lateral Locating Forces.





Therefore the ABS system limits wheel slip by regulating the application of brake force while providing the shortest possible stopping distance.