A method for evaluating instantaneous frequency of a mechanical excitation exerted on a motor vehicle wheel by the uneven surface of a road, based on measurements of observable parameters such as those related to the instantaneous height of the chassis and/or the wheel of the vehicle. The method includes a filtering procedure producing successive estimates of the instantaneous height of the chassis and of the wheel, a lag extracting procedure, producing an estimated value of the time lag between the height estimations, and a frequency estimating procedure, producing the desired evaluation of the frequency based on the estimated time lag value.