Effect of weight transfer on a vehicle’s stopping distance

Abstract

As a braking vehicle decelerates, friction forces between the tires and road produce a torque about the vehicle’s center of mass. This effect, called weight transfer, removes weight from the rear wheels and results in a minimum stopping distance that is in general longer than that given in the usual textbook treatment. In this paper we present an analysis of the minimum stopping distance problem taking into account the effect of weight transfer on (i) nonskidding vehicles and (ii) front- or rear-wheels-skidding vehicles. Expressions for the minimum stopping distances are given for both cases in terms of vehicle geometry and the coefficients of friction. In the case of nonskidding stops we obtain an expression for the optimum brake ratio which will allow all wheels to simultaneously brake at the point of incipient skid. Under this condition a minimum ’’textbook’’ stop is achievable in principle, but only on a given road surface. These results are found to be in qualitative agreement with measured stopping distance data.