Method for identifying a change of rubber mixtures with an extruder for producing tyre components, comprising the following steps: a) providing a first rubber mixture, comprising different mixture constituents, with an extruder, b) continuously changing the first rubber mixture for a second rubber mixture at the extruder, wherein a rubber material is delivered from the extruder opening over a certain time period as a mixture comprising the first and second rubber mixtures, c) positioning an x-ray device comprising a signal source for generating an x-radiation and a detector for receiving an x-radiation in the outlet region of the extruder, d) irradiating the surface of the rubber material (2, 4, 5, 6) emerging from the extruder with the signal source of the x-ray device, wherein at least part of the irradiation is adsorbed by the rubber material (2, 4, 5, 6), e) receiving the radiation allowed through the rubber material (2, 4, 5, 6) with the detector for receiving the x-radiation, f) evaluating the received x-radiation and determining an absorption coefficient, g) determining the change in the measured absorption coefficients during the change from the first rubber mixture to the second rubber mixture, wherein the absorption coefficients are established by the specification of the mixture of the rubber compound to be produced, h) identifying two transitional regions (7, 8) in the rubber material in the outlet of the extruder, wherein the first transition is the mixture transition from the first rubber mixture to the mixture comprising the first and second rubber mixtures and the second transition is the mixture transition from the mixture comprising the first and second rubber mixtures to the second rubber mixture, i) identifying the rubber material comprising the first and second rubber mixtures, j) removing the unpure rubber material from the first and second rubber mixtures from the production process, k) continuously carrying on with the extrusion process with the second rubber mixture. a) providing a first rubber mixture, comprising different mixture constituents, with an extruder, b) continuously changing the first rubber mixture for a second rubber mixture at the extruder, wherein a rubber material is delivered from the extruder opening over a certain time period as a mixture comprising the first and second rubber mixtures, c) positioning an x-ray device comprising a signal source for generating an x-radiation and a detector for receiving an x-radiation in the outlet region of the extruder, d) irradiating the surface of the rubber material (2, 4, 5, 6) emerging from the extruder with the signal source of the x-ray device, wherein at least part of the irradiation is adsorbed by the rubber material (2, 4, 5, 6), e) receiving the radiation allowed through the rubber material (2, 4, 5, 6) with the detector for receiving the x-radiation, f) evaluating the received x-radiation and determining an absorption coefficient, g) determining the change in the measured absorption coefficients during the change from the first rubber mixture to the second rubber mixture, wherein the absorption coefficients are established by the specification of the mixture of the rubber compound to be produced, h) identifying two transitional regions (7, 8) in the rubber material in the outlet of the extruder, wherein the first transition is the mixture transition from the first rubber mixture to the mixture comprising the first and second rubber mixtures and the second transition is the mixture transition from the mixture comprising the first and second rubber mixtures to the second rubber mixture, i) identifying the rubber material comprising the first and second rubber mixtures, j) removing the unpure rubber material from the first and second rubber mixtures from the production process, k) continuously carrying on with the extrusion process with the second rubber mixture.