Wide tyre impact results a cornerstone for change

The Truck Industry Council (TIC) and the National Heavy Vehicle Regulator (NHVR) have released the findings of the latest research project investigating the impacts of wide tyres.

Although wide single and ultrawide single tyres have been available for decades internationally, until now, TIC said, there has never been a substantial study focusing on Australian road construction – in particular sprayed seal unbound granular pavements.

According to TIC, this knowledge has always been a barrier to the adoption of next generation wider tyres in Australia.

To address this, a large-scale testing program using the National Transport Research Organisation’s (NTRO) Accelerated Loading Facility was conducted.

Nine identically designed pavements were constructed, with each loaded repeatedly to determine the relative rate of pavement wear for each tyre.

The results showed the pavement deformation rates for both the dual tyres and single tyres were within a similar range, and the 255/70R22.5 dual tyres caused the highest deformation rate.

The comparative pavement wear of super single tyres was not as sensitive to modest variations in inflation pressure, when compared to duals.

“Taking a real-world perspective on the comparatively small differences in pavement wear found, the pavement damage exhibited by the commonly used 11R22.5 dual tyre configuration was notably influenced by inflation pressure, with the highest damage observed when these tyres were over-inflated – a common occurrence in practice,” said TIC Technical Officer, Paul Caus.

“In addition to the finding, day-to-day use of single tyres make it easier for drivers to check tyre conditions, monitor inflation pressures, and inspect brake components reducing the risk of overheating brakes and wheel end fires.”

In real world conditions, Caus said, it can be expected that the wider adoption of wide tyres would not cause a discernible increase in road pavement wear.

“TIC’s view is that there is no justification in limiting axle masses when using appropriate wide single tyres given the improved vehicle stability and efficiency they bring,” he said.

“They should be permitted to operate at the same mass as equivalent dual tyred axles.”

The project, led by TIC, was funded by the NHVR’s Heavy Vehicle Safety Initiative and supported by the Australian Government.

NHVR Chief Safety and Productivity Officer, David Hourigan, welcomed the report’s findings.

“The findings of this report will be of great importance to equip road managers and the NHVR with the knowledge needed during consideration of vehicle load limits and the benefits provided by super single tyres,” he said.

According to Smedley’s Engineers Managing Director, Robert Smedley, this will become a cornerstone piece of research.

“It will lead to industry wide improvements in safety and environmental impacts of transport,” he said.

“I’m proud to have been a contributor to this body of work that will have a positive impact for generations to come.”

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