The increasing importance of climate change and stricter regulations for greenhouse gas emissions raise the pressure on the automotive industry to develop more efficient products. Besides a reduction of emissions by new combustion engines, electric vehicles are being introduced to lower the fleet fuel economy. Especially this new drivetrain technology benefits from an improved driving resistance of the vehicle, as an increase in range is highly valued for current electric vehicles. The aerodynamic drag, a considerable contribution to the driving resistance, therefore plays an important role in automotive development. With a significant contribution to aerodynamic drag, the wheels and surrounding wheelhouses are considered to have potential for possible improvements and are currently one of the focuses of research. This thesis examines the aerodynamic flow in a rear wheel arch of a low drag electric sedan to identify areas of potential improvement and derive recommendations for future developments. Three major parameters of the rear wheelhouse geometry are therefore modified and their influence on the aerodynamic drag and the flow field is assessed. These include the wheelhouse radius, wheelhouse width and the wheel track. For this purpose, Reynolds Averaged Navier Stokes (RANS) simulations are used to both calculate the effect of the variations on aerodynamic drag and analyse the origin of changes in the flow field. For parameters where it is possible, tests on a detailed full scale model are carried out in a modern full scale wind tunnel.