An off-road tire model has been developed for use in vehicle handling studies.  A baseline force and moment model was first developed for the studied tire by performing force and moment testing on a rolling road.  Forces and moments were recorded in response to slip angle, camber angle, and vertical load inputs and a Pacejka Magic Formula model was determined.  This baseline force and moment tire model is applicable for a dry asphalt driving surface.

Next, off-road tire testing was performed on a passenger tire by using a portable tire test rig.  The tire was subjected to slip angle sweeps at various vertical loads while being driven on dry asphalt, dirt, and gravel.  Lateral force scaling factors for use in the Magic Formula were obtained for the dirt and gravel driving surfaces. The scaling factors were then applied to the studied tire to extend its lateral force behavior on dry asphalt to dirt and gravel.  The off-road tire model was then used in commercially available vehicle simulation software to simulate vehicle handling behavior on dirt and gravel driving surfaces.  The vehicle simulation results were compared to actual vehicle data for maximum speed vs. radius for the vehicle going into sliding.