1. A method for determined a frictional value between a motor vehicle tire and a road surface, which comprises: ascertaining values of vehicle speed, angular acceleration of a vehicle wheel, and brake pressure; calculating a wheel slip from the values; approximating a dependency of a coefficient of friction between a road surface and a vehicle tire from the wheel slip with a non-linear approximately equation; estimating a current estimation value for the coefficient of friction with a recursive estimation algorithm from measurement values previously ascertained during a preceding measuring instant; and determining a frictional value between the motor vehicle tire and the road surface from the coefficient of friction estimated with the recursive estimation algorithm.