This thesis presents a preliminary dimensioning methodology for the architecture of a racing motorcycle prototype positioned, in terms of target geometry and performance, between Moto3 and Moto2 categories. The objective is to identify a coherent set of geometric and functional parameters suitable for the early design phase, with particular focus on the rear vehicle layout, final transmission, chain pull and anti-squat behaviour. The work is based on a parametric and iterative approach. First, a geometric benchmarking activity was carried out using CAD models and 3D scans of reference motorcycles, in order to define plausible design ranges for the main vehicle parameters.