Abstract — A Scalable Axial Flux Motor (AxMDM) with geometrically adjusted U-core laminations and an NdFeB-magnet equipped GRP disc rotor was developed, assembled and tested. The novel machine concept is easy to fabricate and can be scaled by the number of the phase elements and the number of the rotor-magnets to meet different requirements for output torque and power. It shows a high torque-to-weight ratio and has an excellent utilization rate of the magnet material. In this paper, the geometry of the U-core laminations is investigated in depth. Therefore, the tooth width of the U-core laminations was varied under adjustment of slot width and stator MMF (ampere-turns). The corresponding output torque was simulated for each combination, and the simulation results were verified with the measurement results of the latest prototype. With this investigation, an optimum between the active weight and the torque output can be found. Furthermore, design rules for the U-core geometry in terms of torque smoothness and torque overload capability can be derived.