The objective of this paper is focused on the computer modelling and dynamic simulation of a coach with damaged wheel and the assessment of these negative effects on a track. The article is composed of two parts. Firstly, problems about the operation of rolling stocks with damaged wheels are described. There are also mentioned diagnostic systems installed on a track for detection and assessment their negative impacts on a track. The second part of the article is dedicated to computer modelling of a coach running on a railway track with the damaged wheel, in this case with the wheel-flat. For these purposes the virtual model of a coach were created. After simulations of its running there were performed analyses needed for the evaluation of its negative impacts on a railway track.