Typical production vehicle testing includes testing of a vehicle towing a trailer to evaluate powertrain thermal performance. In order to correlate tests with simulations, the aerodynamic effects of pulling a trailer behind a vehicle must be estimated. Since during real world conditions a vehicle encounters crosswinds most of the time, the effects of cross winds on the drag of a vehicle–trailer combination should be taken into account. Improving the accuracy of aerodynamic forces for a vehicle-trailer combination should in turn lead to improved simulations and a better prediction of thermal performance. In order to best simulate real world conditions, a study was performed using reduced scale models of an SUV and a pickup truck towing a medium size cargo trailer. The vehicle and trailer combinations were tested in a full scale wind tunnel. Utilizing a full scale wind tunnel allowed for very low blockage conditions and testing at large yaw angles, with both the vehicle and the trailer on the wind tunnel balance pads. This unique setup allows for the measurement of all aerodynamic forces and moments on the vehicle, which could be used to improve vehicle dynamics modeling of a vehicle-trailer combination. The results of this paper show that the forces and moments on a vehicle-trailer combination change significantly at large yaw angles, and that zero yaw testing is not sufficient to predict the aerodynamic performance.