The new technology, said the Japanese rubber and tire company, is expected to lead to the development of winter tires “with dramatically improved ice performance”.
When running on ice, the tire’s inability to make firm contact with the road surface due to the watery film generated by the icy surface reduces the tire’s grip.
Studless snow tires use water absorbing agents and tread patterns with high drainage performance to counter the watery film.
However, when observing tires’ contact with the road, it has been difficult to distinguish the area where water is between the road surface and the rubber from the area where the rubber is in direct contact with the road surface, e.g. the real contact area, Yokohama explained.
This impacts the accuracy of degree of real contact.
As part of the joint project, Yokohama and Kanazawa University developed a specialised testing machine equipped with a high-speed camera that enables visualisation of the tires’ contact with the ground and identifies the real contact area.
By establishing an analytical technique for digitising contact images, Yokohama Rubber said it had also succeeded in numerically evaluating the water absorbency and drainage of tire rubber.
The testing machine is able to observe frictional behaviour between a rubber sample and ice or a smooth transparent disk used to replicate ice at speeds of up to 50km/hr.
The high-speed camera can take one million micro-level images per second of the tire rubber’s contact area with the road surface. It also can simultaneously measure the frictional force during the test.
Images taken with this testing machine are dark only in the real contact area. Rubber that includes a water-absorbing agent shows darkness over a wider area than rubber that does not include the water-absorbing agent.
Yokohama unveiled its three-year consumer tire strategy, the Grand Design 2020 (GD2020), this year. Among others, the blueprint aims to gain “performance leadership” in winter tires supplied in the Japanese, European, and Russian markets.
Yokohama said it was using the new technology widely in its development of winter tires, from studless snow tires for Japan to winter tires for the European market and all-season tires.