Estimation of Tyre Deflection and Contact Area of Tubeless Tyre on Firm Surface for Traction Studies

The objective of this study was to investigate the effects of normal load and inflation pressure on the deflection and contact characteristics of a tubeless tyre, which are important factors for determining the performance and efficiency of agricultural tractors. The tubeless tyre was tested at four levels of normal load (7.35, 9.81, 12.26 and 13.73 kN) and eight levels of inflation pressure (68.9, 82.73, 96.53, 110.32, 124.1, 137.9, 151.69 and 165.47 kPa). The results showed that the normal load had the most significant influence on both contact area and deflection of the tubeless tyre, followed by the inflation pressure and their interaction effect. The Komandi model with new coefficients was most suitable for estimating the contact area of the tubeless tyre, as indicated by high R² (0.979), low RMSE (4.465 × 10⁻³) and low MAPE (3.61%), and the Krick model with new coefficients was most appropriate for predicting the deflection of the tubeless tyre, as shown by high R² (0.973), low RMSE (2.34 × 10⁻³) and low MAPE (3.60%). The findings of this study can help to improve the design of tubeless tyres and to select the operating parameters for optimal performance and efficiency of agricultural tractors.