Calculation and operational assessment of tyre contact areas in the tractor-and-trailer unit

This paper deals with the verification of models for the calculation of the contact area with the soil using data measured during the testing of a tractor-and-trailer unit. The main emphasis was put on the method of calculating the contact area by means of a super ellipse. The comparison included calculation models with the input parameters of contact length and contact width of the tyre. These parameters were compared with values measured in the field where the main variables were tyre dimensions, inflation pressure and load. Results of comparisons show that the method of calculating the contact area using a super ellipse exhibited the best match with the measured values of all compared calculation models (81% in super ellipse with measured half-axes and 75% in super ellipse with calculated half-axes). As to trailer tyres, the match of measured values and those calculated using a super ellipse was even 95%. In the second step, also some empirical models for calculating the contact area were compared with the measured data, not entered by contact length and contact width as variables. Some of these models show a very good match with the measured data, which can be compared, or it is even higher than the calculation by means of a super ellipse. With the specified tyre deformation, however, we consider the model of calculation using a super ellipse as more appropriate for determining the size of contact area as it focuses on the geometry of tyre contact with the ground.