This paper aims to present the new method developed to generate optimized spiral bevel gear surfaces. Thanks to a complex non linear finite element model, the geometrical gear meshing positions under operational loads are first precisely computed. These meshing positions are then used as inputs of a calculation process that seeks to define the best tooth surface topography. So far, this activity was based on sensitivity studies conducted directly by the designer, which led to repeat calculations whose progress was difficult to control. EUROCOPTER uses now optimization algorithms to compute automatically the surfaces of the tooth contact flanks. This approach leads to higher performances of the gear while reducing the development time. This paper describes the new process implemented to design the tooth shape, and illustrates its interest through an example.