An existing wind tunnel setup for measuring full scale automobiles with an external under floor balance is modified for accepting a long articulated six-axle truck models of 50% scale. These exceed by far the dimensions of the existing wheel supporting pads. The tests require the measurement of all six force and moment components at yaw angles up to 16°. Therefore, the front of the truck model extending beyond the ordinary test section is supported with instrumented air bearings under the wheels. In this manner friction forces altering the drag and side force measurements of the balance are reduced to a minimum.