Agricultural energy usage is an important topic among agricultural industry producers, manufacturers and regulators. Zoz and Grisso (2003) stated that prior research shows between 20 and 55% of tractor energy is lost at the soil-tire interface. This transfer of power between axle and drawbar has been identified as one of the greatest inefficiencies in agricultural field operations. Understanding the stresses at the soil-tire interface would provide insight into the current state of tire traction development, data for soil-tire interface discrete and finite-element models, and information for future tire designs.

This paper presents a measurement system to quantify the shear and normal stresses at the soil-tire interface of an agricultural tractor tire, allowing associations to be made concerning the distributions of these stresses across and along the tire footprint. Shear and normal stress measurement systems were developed in the laboratory and the normal stress sensing system proven in the field. Additionally, a dedicated data acquisition system was also developed and proven in the in-field environment. Test results show the system capabilities as well as information on the challenges of drawing general, consistent conclusions concerning the stresses developed between a tire and the soil at field working speeds in agricultural soils.