Various mountain bike trails exist in South Africa, but their difficulty ratings are generally unknown. By classifying the trails, risk of injury and uncertainty can be limited as information are provided on the difficulty of the trail. In creating a Trail Classification System (TCS) the principles of Vehicle-Pavement Interaction (V-PI) can be applied to develop an objective evaluation of trail difficulty. The objective of this paper was to describe the different aspects that contribute to the degree of difficulty of a mountain bike trail and adopt an existing trail rating system through application of V-PI data. Based on the information in this paper, it is concluded that trail roughness affects the measured riding quality value of a section and trail gradient is the main contributor to difficulty of a mountain bike trail in terms of physical exertion. It is recommended that the proposed TCS be implemented on mountain bike trails.