The principle of the method specified is vertically compressing a length of pipe supported horizontally between two parallel flat plates moved at a constant speed which is dependent upon the diameter of the pipe, measuring the force and the deflection, plotting the force versus deflection, and calculating the ring stiffness as a function of the force necessary to produce a deflection of 0,03 nominal diameter diametrically across the pipe. Applies to pipes having a circular cross-section.