A number of vehicle users pay attention to the impact of changes in the car body geometry during long-term use on the safety level. However, this issue has not been properly dealt with in research studies. The aim of this study was to identify changes in the floor panel, to develop a model to forecast the geometry during the car use and to identify the points which undergo the maximum displacement. The paper presents the effect of the car mileage on the floor panel condition, taking into account variable environmental factors. In the course of the study, the position of points fixing the front suspension, front bench and rear suspension was determined, as was the position of points situated on parts of the load bearing structure of the car body. The results were used to develop a model for forecasting changes of the floor panel geometry during car use. The probability of changes in the floor panel geometry was found to increase with the mileage. The probability of reaching the maximum permissible geometric changes (3 mm) in a floor panel is accurately described by the probabilistic model in the form of the Rayleigh distribution. Diverse models of the floor panel geometry changes were obtained depending on the environmental conditions and type of the base points under analysis.