The work examines the causes of wear of carbon inserts used in current colectors of urban passenger public electric transport. The study of the contact wire and carbon inserts wear causes using various methods, including testing the hardness of samples of carbon inserts and contact wire is described. A research to determine the chemical composition and microstructure of contact wire samples was also carried out. The wear of the carbon inserts over a time period of 100 hours was determined on the testing equipment. Based on the data of the chemical analysis of the material samples and their microstructure, the research results the reasons for the increased wear of the carbon insert. The conclusions analyse the main aspects leading to increased wear of carbon inserts.