Tire manufacturers are obsessed with understanding the wet grip properties of their tires. Researchers from Michelin have now found a way to visualize what happens when tires lose their grip on wet surfaces. They hope it will support the design of more efficient tread patterns.
, the track was flooded with a layer of water 8 mm thick. This represents fairly extreme flooding, and so guarantees hydroplaning. In a separate paper to which I was given advance access, the authors say that in practice,In many experiments , fluorescent dye can be mixed into this water, to improve the image contrast between it and the tyre contact patch. Here, they used an additional technique.
What they found surprised them. In each of the wide, longitudinal grooves that go around the central circumference of the tire, they saw two white filament-like features or columns within the water. In the narrower longitudinal grooves closer to the sidewalls of the tire, just one of these white columns was visible.
within the tread patterns. You can think of cavitation as very tiny cavities that continuously form and collapse in liquids that have been accelerated to high speeds. They’re common near propeller blades or in pumps, and they have major implications in how water behaves. The bubble columns also weren’t perfectly symmetrical and parallel to the groove walls – counter-rotating swirls or vortices appeared at the junctions between the grooves and the lateral slits. This is first time such flow behavior has been seen. The authors say that this might be due toas water moves from the slits and into the grooves.
** In addition to this ‘indentation’ form of grip, in dry conditions, tire rubber can make an even more intimate form of contact. Called molecular adhesion, it involves chemical bonds between the tire and road surface continuously forming, stretching and breaking as the tire rolls along.PS: This article was inspired by my upcoming book, Sticky: The Secret Science of Surfaces. Chapter 5 of that book delves into much greater detail on all things tires .