The vibration monitoring is largely used to detect the defects in the revolving machines. The determination of the best sensor positions is one of main research goals in the domain of the conditional maintenance. This paper proposes a numerical methodology based on a finite element model and a spectral analysis in order to find optimum sensor positions. The bearing is considered as a key component in vibration propagation from the moving parts to static ones. In this paper, we use an analytical bearing model and its numerical implementation in a FE code. The tangent stiffness matrix of the bearing element is calculated by the Newton-Raphson method and then introduced into the modal and spectral analysis. The technique of “Mode Shape Summation Plot” (MSSP) is adopted to find the most sensitive zones to usual defects. The proposed numerical approach gives good agreements with the experimental results. A real grinder modeling shows its interesting industrial applications.