This project aims to provide insights and a better understanding of power losses in cycling, with a particular focus on professional road cycling and the vibration losses experienced during rough road stages such as Paris–Roubaix. While aerodynamic drag and pure rolling resistance are well-documented, vibrational losses, caused by the excitation of the bicycle-rider system over uneven roads, are often overlooked or inadequately modeled. This thesis investigates vibration-induced losses up to speeds of 30 km/h using a controlled coast-down experiment over a simulated cobblestone surface, isolating their contribution from aerodynamic and classical rolling resistance forces.
The results show that vibration losses can reach up to 350 W and account for as much as 60% of total power losses under certain conditions. A clear quadratic trend with respect to speed was identified, challenging the conventional assumption that such losses can be included in the speed-independent rolling resistance term. Posture and tire pressure were also found to significantly influence these losses: riding out of the saddle consistently reduced vibration losses, while higher tire pressures led to greater total power loss due to increased vibrational dissipation. In contrast, rider behaviour, defined by varying levels of muscle contraction, did not yield consistent trends under the current experimental results.
To describe and better understand these dynamics, a simple empirical model was proposed, incorporating a quadratic dependence on speed, a linear dependence on pressure and a posture-dependent scaling factor. While intentionally limited in complexity, the model fits the observed data well and captures key interactions between the main influencing variables. These findings support the need to model vibration losses as a separate, speed-dependent component of total resistance. They also offer a useful starting point for future research focused on refining resistance models and enhancing energy efficiency in cycling.