Tribological loading changes the microstructure of the materials in contact, e.g. in coarse-grained metals first grain refinement occurs, afterwards cracks form and finally wear particles are removed. The stress field has to be known to be able to analyse the crystallographic systems carrying plasticity. The stress field under tribological load is rather complex based on its multiaxiality, location and time dependency. In our approach, experiments are combined with (crystal plasticity) FEM simulations. The experiments are conducted on single crystals and designed in such a fashion that only in some crystal orientations deformation twins were formed. The activated twin systems were analysed. The FEM was used to calculate stress fields with the experimental parameters. The required complexity of the material model was investigated by varying work hardening behaviour, elastic and plastic anisotropy. These stress fields were used to calculate the resolved shear stresses on the twin systems in the experimentally investigated crystal orientations. If the twin systems with the highest calculated resolved shear stresses arise on the experimentally identified twin systems, the stress field is presumed to be valid. This study shows that a plastic anisotropic material behaviour is required to adequately describe the stress state under tribological loading.