Intense competition between top-level track cycling athletes requires research to make optimisation possible. In this context, the energetic efficiency of roller chain drives is studied to improve understanding of loss sources and to propose improvements. Losses in chain drives are mainly caused by the meshing/un-meshing process of chain links on the sprockets. However, a preliminary study shows that losses caused by the motion of rollers along their associated tooth profile have a significant influence. The aim of this paper is therefore to explore this phenomenon. An original 2D quasi static model of a two-sprocket drive is presented. The global drive kinematics (including transmission error) is determined using specific sub-models for the tight and slack strands. A local sprocket sub-model is then introduced to calculate link tension, roller/ sprocket contact force and roller location. This model can be used for different tooth profile geometries. Based on the results provided by the global and local model, the presented model calculates drive efficiency, considering the losses caused by meshing and roller motion. A comparison with literature is done to ensure the model validity.