In this paper an adaptive observer-based method is proposed for the estimation of the side slip angle of road vehicles. The method is based on a Linear Parameter Varying (LPV) model of yaw-roll dynamics, which contains unknown parameters and time varying variables. In order to estimate the unknown parameters of the model a grey-box identification method is proposed. Since the adhesion coefficient changes during vehicle maneuvers this variable is estimated as a scheduling variable in the control-oriented LPV model. The three-step estimation procedure is illustrated through simulation examples. lf lṙ ψ c c © © Fb,fl