The invention relates to a method for determining the state of surface defects in the running tread of rail vehicles for the determination of an optimum profiling timing of disc-braked wheel sets. The invention is based on the object by means of a reliable monitoring method and in compliance with the respective degree of damage to the wheel tread of rail vehicles to determine an optimum time and a necessary depth of the reprofiling of the tread, so that the running performance of the wheels can be increased significantly by the limit dimension. This is inventively achieved in that
the wheel contact surfaces of disc-braked axles subjected to ultrasonic surface waves, the sound attenuation of the ultrasonic surface waves (Rayleigh waves) according to the relation $${\mathrm{S}}_{\mathrm{w}}\mathrm{=}\frac{\mathrm{20}\mathrm{\times }\mathrm{Ig}\begin{array}{l}{\underset{}{\mathrm{H}}}_{\mathrm{U.N}}\\ {\mathrm{H}}_{\mathrm{U\; n}\mathrm{+}\mathrm{1}}\end{array}}{\mathrm{.DELTA.s}}$$ measured and / or determined, wherein
S _w - sound attenuation
H _U - amount of the net signal amplitude in dB
Δ s defined path in mm
means it determines the width and the depth of the injury, classified this injury in damage zones and damage classes and assigned to and from the necessary Reprofilierungstiefe and Reprofilierungszeitpunkt the wheel tread is determined.