The effective evaluation of loads acting on a vehicle is a fundamental challenge in several engineering applications. Where possible, instruments such as load cells are used for a direct measurement of these loads, otherwise local strain measurements can provide an indirect determination of forces or pressures reaction. In this case, an adequate number of strain measurements in proper location is required to achieve correct load measurements, using a pseudo inverse method. In the present work, a variation of the classical method of applied forces calculation from the deformation data is presented for automotive applications, in particular in the case of reduced detected deformations number, lower than necessary for loads determined by static equilibrium. Finally, the method is tested on a real case study, where the aerodynamic downforce generated by the rear wing of a high-performance car is measured.