System for measuring motor bearings consumption of railway vehicles, comprising: a phonic wheel, arranged to be fixed to a shaft of a rotor, having a profile including an alternation of teeth and holes; a sensor, arranged to measure a punctual air-gap between the teeth of the phonic wheel and said sensor during rotation of the shaft, said sensor generating a basic sinusoidal signal function of said profile, wherein the basic sinusoidal signal is superimposed to a modulating wave, representative of a radial motion of the shaft, the basic signal and the modulating wave forming a complete signal; characterized in that the sensor further comprises: a control unit arranged to measure a maximum and a minimum amplitude value of the complete signal, said maximum and minimum amplitude values representing the maximum and minimum air-gap between the phonic wheel and the sensor, and for calculating an air-gap swing value; memory means arranged to store said air-gap swing value; wherein said sensor is arranged to send to an external control unit said air-gap swing value when the shaft stops rotating.