The paper presents the analysis of reasons, form and wear of elements of V-belt transmission. Syndromes of loss of driving properties for chosen wheels and V-belts are specified. Methodology of failure evaluation of wheels and V-belts with the application of optical microscope is proposed. The applied measuring set allows for universal analysis of the measurement results. Operation principle of this device and its measuring and analysing abilities are shown. Failures of chosen V-belts and the influence of these failures on accuracy of kinematic features of chosen driving units are evaluated.