Road contact stresses and forces under tires with low inflation pressure

Many field trials have been undertaken to demonstrate the benefits of reduc ing the inflation pressure of the tires of heavily loaded haul vehicles, bu t few carefully controlled laboratory studies have been performed. An earli er full scale laboratory study indicated that tire inflation pressure had f ar less effect on subgrade strains for unpaved, single-layer granular road structures than the tire loading itself, so attention was directed to the b ehaviour of the granular base at the tire tread - road surface interface. I n the present paper, the results of full scale tests performed using a labo ratory apparatus designed to measure the dynamic vertical, transverse, and longitudinal contact forces under tires with varying loads and inflation pr essures are reported. Vertical contact forces were observed to be highly no n-uniform, both across and along the contact patch.