This paper presents a fast method to take into account three dimensional effects in reinforced brushed DC motor used as starter in automotive application. Due to their low cost and simplicity, reinforced starters are used in micro-hybrid vehicles. The specific geometry of such devices induces axial component of the flux which cannot be accounted for by 2D models. 3D finite element models are suitable fur this purpose but their excessive need of CPU time complicates their use in an automatic optimization procedure. The authors propose to identify the overhang effects by using an adapted and corrected 2.5D finite element model which is validated by 3D computations and experiments. Finally, the 2.5D model is implemented in a multi-objective optimization procedure.