In 1996 the European Commission started the COST1 Action 334 ,"Effects of Wide Single Tyres and Dual Tyres" for trucks. The main objective of the action was to establish the relative effects of wide base single tyres and dual tyre assemblies in respect of road pavement damage, vehicle operating costs, vehicle safety, vehicle comfort and environmental aspects (e.g. tyre/road noise). This paper only describes the vehicle safety aspects. The practical research work (mathematical simulation of the truck driving behaviour) was carried out by order of BASt by the former Institute of Automotive Engineering of the University of Hanover and was part German input to the COST 334 action, which will be finished in 2001. To study the driving behaviour and safety of various trucks and units with different tyre combinations and loading conditions was the aim of the study. In this research project a computer-aided simulation in ADAMS was used to investigate and compare the driving behaviour and driving safety of heavy goods vehicles with wide single tyres on their driving axles on the one hand and standard vehicles with twin tyres on the other. The different tyre widths also enabled alterations to be made to the vehicle's chassis, e.g. changes in the frame width, the spring suspension width and the stabiliser setting. Alterations in driving behaviour and driving safety are mainly dependent on the tyre characteristics (cornering stiffness) of the tyre itself. The wide single tyres showed a higher level of lateral stiffness which was reflected by a higher degree of under-steering i.e. safer driving behaviour. This tendency is beneficial with regards to the steerability of a vehicle combination. The altered width of the spring suspension on the drive axle had no influence on the side-tilt stability of the vehicle combination. Only the solo truck profited from the higher roll stiffness of the rear axle, which means a lower danger of a roll over accident. As far as the driving safety is concerned no factor spoke against using wide base tyres on the drive axle. The investigation into the driving stability with defect tyres on the drive axle showed for the very seldom case of tyre defect in a bend (assuming 40 per cent max. transferable side force) no increased danger when using wide base single tyres. In addition to the described safety aspects some more advantages and disadvantages of wide single tyres should be mentioned but without further explanations: The rolling resistance of a single tyre is about 20 per cent less compared with twins. This leads to lower fuel consumption (about 2 per cent for a 40 t unit) and lower CO2 emissions; a higher pay load (130-150 kg) can be realised; the tyre road noise is nearly equal for both tyre combinations; the road wear (rutting) is higher for single tyre equipped trucks, especially on secondary roads. This can be nearly compensated if 385 size tyres are used on steering axles. (A) For the covering abstract of the conference see ITRD no 207828. The reprints are also available at the web - http://www.vti.se/pdf/reports/K18APart1.pdf; http://www.vti.se/pdf/reports/K18APart2.pdf and http://www.vti.se/pdf/reports/K18APart3.pdf.
Abstract