POSSIBILITIES OF REDUCING THE ROLLING RESISTANCE OF COMMERCIAL VEHICLE TYRES AND EFFECTS ON FUEL CONSUMPTION

For commercial vehicles the rolling resistance of the tyres constitutes a high portion of overall tractive resistance and hence of fuel consumption. Tyres were extensively drum tested to establish the influences of the operating conditions, the viscoelastic properties of materials and the design parameter variations on the rolling resistance. The testing schedule was devised to enable factors of influence to be determined. The limits imposed by other performance characteristics such as riding comfort, road adhesion, abrasion behaviour were in many cases deliberately exceeded so that less pronounced tendencies could also be pinpointed. Altogether approximately 150 types of tyres were tested. In addition, small slip angles were included in the tests thus permitting the losses due to transverse forces (e.g. Side wind) to be calculated. In a second series of tests several individual factors were combined, while ensuring that the remaining performance characteristics were not essentially impaired. The systematic preparatory work led to a reduction in the rolling resistance of 20 to 25 per cent. Apart from rolling resistance values the fuel consumption was recorded on the vehicle. These tests were restricted to constant speeds on a level roadway. There was a good correlation between rolling resistance values ascertained on the test rig and fuel consumption recorded on the vehicle. For a truck train of 38 tons at long-distance traffic a reduction of rolling resistance by 20 per cent resulted in a reduction of fuel consumption by 5 to 8 per cent per car according to different operating conditions. (Author/TRRL)