TRUCK TIRE PAVEMENT CONTACT PRESSURE DISTRIBUTION CHARACTERISTICS FOR SUPER SINGLE 18-22.5 AND SMOOTH 11R24.5 TIRES. INTERIM REPORT

Within the last 50 years truck sizes, allowable wheel loads, and tire inflation pressures have increased. In order to establish pavements capable of sustaining the increased loading, the actual loading mechanisms and their magnitudes had to be identified. To identify the magnitudes, static testing was performed at The University of Texas at Austin on a specially manufactured Armstrong 11R24.5 LR-G smooth tread tire and also on a commercially available Goodyear 18-2.5 LR-H wide-base, newly-recapped super single tire. Contact pressure distributions were obtained for the 11R24.5 radial tires at inflation 90 and 105 psi and loaded to 5,000, 6,000, and 7,000 pounds. The 18-22.5 recap bias tire was inflated to 85 and 100 psi and tested at wheel loads of 8,000, 10,000, and 12,000 pounds. The pressure data acquisition system used to obtain the tire contact pressures consisted of three main components: a load frame (powered by a manual hydraulic system) for mounting and loading the test tires, Fuji pressure sensitive film to record pressure distributions, and a film analysis package using the Adage 3006 Graphics system to process the pressure distribution data. The contact pressure data were presented as numerical pressure distribution maps and also illustrated as two-dimensional spectral graphics and three-dimensional surface plots. The experiments indicated that for the 11R24.5 tire and the 18-22.5 tire, increased wheel loads at constant inflation pressures generally resulted in more uniform contact pressures throughout the contact area. The same increased wheel loads were also accommodated by a lengthening of the contact area. On the other hand, increased inflation pressures at constant wheel loads resulted in a reduction of contact area and increased contact pressures in the contact patch's central region. Low inflation pressures tended to cause the wheel load to be distributed more heavily to the contact patch's central area for the radial tire and more heavily to the sidewall contact area for the bias tire.