Wear of mechanical components is a problem due to the related material and energy consumption. Its reduction is important for sustainability particularly according with the Goal 12 “Responsible Consumption and Production”. In order to design components with lower wear experimental tests are usually performed. The most common configuration used is the pin-on-disc one where a spherical pin is put in contact with the plane surface of a disc. While in certain real contacts the contact pressure does not vary much, the wear of the surface specimens during running of a pin-on-disc test, commonly performed at constant normal load using a spherical pin, produces variations. The aim of this work is to investigate how significant and rapid the reduction of pressure throughout the test can be. An estimation of the pressure variation is made based on the results of two tests in different extreme conditions: wear occurring on the spherical pin only and wear on the flat surface of the disc only. The analysis shows that the pressure reduction in the first case is faster than the second one.