A method for detecting wear of a tire involves at least one sonic wear gauge emitting an acoustic footprint noise that includes several acoustic footprint elementary frequency components. The stable mounting base is in the form of a weighted shallow robust body having a length and breadth substantially greater than its thicknes. Thus, a depletion region of the photodiode, formed when the sensor operates, extends to the exposed surface of the photodiode through the inner region of the photodiode, so that it is possible for the photodiode to normally absorb short wavelength light as well as long wavelength light at its depletion region.