Yokohama engineers at the company’s headquarters in Japan have proposed the concept that a "danger zone" exists when ice can be more slippery.
According to the company, understanding what makes ice slippery was the first step in creating a new generation of winter tyres better able to deal with this dangerous condition.
Tyre engineers have long understood that the very act of driving a car on ice makes the ice more slippery. The weight of the car and the friction of the tyre rolling acts to melt the ice under the tyre. The layer of water between the ice and tyre acts like a lubricant, reducing the traction the tyre can achieve. The engineers at Yokohama Rubber Co. studied the phenomenon and discovered that the thin film of water created by the tyre actually grew when the temperature was between minus six and zero degrees.
The engineers learned that it was between these same temperatures that the vehicle’s ability to stop or turn became seriously impaired. Measuring the thickness of a film of water seven times thinner than a human hair became crucial to understanding how to deal with the threat it posed to safe driving.
Yokohama engineers determined that a layer of water thicker than 10 micrometres between the tyre surface and the ice presented a crucial challenge to winter tyres: Tyres that could cope with the thinner layer of water created at colder temperatures suddenly couldn’t handle water 10 micrometres or greater and began to hydroplane. (1.0 micrometre is one/one-thousandth of a millimetre).
The next question was how to get rid of a film of water so thin it could barely be measured. Despite how they appear to the naked eye, neither ice nor the rubber surfaces of a tire are completely smooth. Viewed under a microscope, tiny undulations in both surfaces can be seen – undulations that capture water between them. The challenge for the Yokohama engineers was to find a way to eliminate that water. They turned to two technologies that literally help the tyre to absorb the water between the ice and tyre surface.
The first creates tiny suction cups that pick up water; the second literally absorbs water and then releases it. Both technologies are actually part of the solid rubber areas of the tyre and so small that they aren’t visible without a microscope.
The absorptive compound can handle from 10 to 60 micrometres of water created in the danger zone, says Yokohama. Two new tyres from the company – the Yokohama Ice Guard IG 20 for automobiles and the Yokohama Geolandar I/T G072 for light trucks and SUVs – incorporate the new absorptive technologies.
