Impact of High-Pressure Tires and Single-Tired Axles in Oregon

Abstract

The growing concern in Oregon in the early 1990s that the use of single tires on the nonsteering axles of trucks may be growing and leading to increased damage to pavements is addressed. An associated concern was that tire pressures may be increasing and contributing to increased damage. Single tires are used in two ways on nonsteering axles. Wider-than-normal tires (wide-base) may be used instead of traditional dual tire assemblies, or singling out of dual tires may be done, where the inside tire of the duals is removed. An extensive survey of trucks was conducted at Oregon's five ports of entry in 1992 to establish the pattern of use of single tire and tire pressures. The data were compared with those available from studies conducted in Oregon in 1986 and 1989. There did not appear to be a growth in use of single tires or a trend of increasing tire pressures. However, the data collected previously for single tire use was limited. The surveys conducted in 1992 showed that single tire use varies throughout the state, depending on the commodities hauled in an area. Singling out tends to be used where relatively light articles are being hauled, whereas wide-base tires appeared to be concentrated with trucks hauling forest products. The surveys indicated that less than 10 percent of trucks used single tires on nonsteering axles. The use of single tires on nonsteering axles does not appear to be a significant problem. However, on the basis of the analysis conducted in this study, some control may be appropriate because such tires could cause more damage than similarly loaded dual tires. Partial singling out of tandem axles has the potential to be particularly damaging. Such axles have six tires instead of the usual eight. However, there are many options for using single tires and some are used with axle configurations that cause less pavement damage than alternatives using dual tires. An example of this would be a tridem axle with single tires versus a tandem axle of the same weight using dual tires. Any control of single tires should not limit their use with less damaging axles.