Is there a non-pneumatic—or airless—tire in your future? Is this a relatively new concept making its way in the tire industry?
Regular readers of Tire Business will have noted a number of announcements in recent months from tire manufacturers around the world concerning non-pneumatic concepts that promise to offer pneumatic-like performance.
While Group Michelin's “Tweel” tire/wheel hybrid has garnered the most attention, Hankook Tire Co. Ltd. has grabbed a few headlines of its own for its “i-Flex” polyurethane airless tire.
Meanwhile, Bridgestone Corp., Sumitomo Rubber Industries Ltd. (Gyroblade) and Yokohama Tire Corp. have all also shown non-pneumatic concept tires in recent years.
Many alternatives to the pneumatic tire have been proposed in the past, including non-pneumatic versions, such as the French Roussel elastic wheel that dates back to the early 1900s.
In fact, in 1906 a demonstration was organized in the form of a public race that took place April 17-26 in France over a distance of 1,314 miles—passing the cities of Dijon, Valence, Lyon, Marseille and Nice, ending in Paris—for the purpose of testing a variety of elastic wheels.
At the start of the race there were 10 contenders; by the time they reached Marseilles, four remained and only three finished the race. The results were pitiful indeed and marked the end of the Roussel elastic wheel and others of this type.
The pneumatic tire remained king (see the accompanying poster touting the Roussel elastic wheel), but now we're seeing a renaissance, of sorts, of the airless tire, or wheel, or hybrid of tire and wheel.
The i-Flex is said to make use of eco-friendly materials, and its construction is reportedly centered on a new polyurethane type of uni-material designed to maximize the tire's eco-friendly potential, with the material enhancing energy efficiency and the tire's recyclability.
Also mentioned was that Hankook is integrating new tire construction techniques to simplify the manufacturing process, thus reducing the tire's carbon footprint.
Unfortunately, neither details of the tire's construction nor tire performance characteristics—such as structural integrity retention, tread life, skid resistance under wet and dry road surface conditions, rolling resistance, tire manufacturing precision and uniformity, etc., nor the cost/price of this new polyurethane tire—have been indicated.
On and off over the last 10 years, Michelin has publicized its Tweel airless tire/wheel system.
The tire maker unveiled the Tweel publicly at the 2005 North American International Auto Show in Detroit, indicating the then-concept “comprises a rigid hub connected to a shear band by means of flexible, deformable polyurethane spokes and a tread band—all functioning as a single unit.”
Last March, Michelin disclosed it was opening a plant in North America dedicated to producing the X Tweel airless radial tires for commercial applications, boosting output of its X Tweel SSL skid steer tires and beginning production of the new X Tweel Turf as original equipment.
The fact that these—and other companies'—airless concepts all seem to be based on polyurethane stirs interest in this material as a potential alternative to rubber.
Years ago, during the radialization of the U.S. tire industry (Ford Motor Co.-Michelin North America Inc.-Sears, Roebuck & Co., 1965-1970) period, I became interested in significantly simplifying tire structures and tire manufacturing processes. I used DuPont Co.'s then-recently introduced “Kevlar” aramid cord material, called “Fiber B,” in conjunction with liquid reaction injection molding, a single polyurethane compound tire body and an styrene-butadiene rubber (SBR) tread compound, in combination with a simpler tire construction, but still based on the radial-ply tire architecture.
I thought this would be a more economical solution to the fundamental problems of ride harshness, boom and tire pull, for which steel cord-belted radial-ply tires were notorious on many vehicles.
Then, in 1970, Firestone Tire & Rubber Co. presented us at Ford with a cordless uni-material polyurethane pneumatic tire, produced by a simplified manufacturing process. No process details were provided, but I suspected that it was based on the use of centrifugal casting and reaction injection molding. Firestone called it the “cast tire.” I never saw it again.
My initial interest in polyurethane was based on the material's unique set of remarkable properties. But the problem of high cost then, as well as today—in fact twice the cost of standard tires made from steel or textile cords and rubber—was, in my view, a severe drawback to market entry, and I decided not to pursue it.
Producing polyurethane pneumatic tires is not as easy as you might think. For example, when using a uni-material (elastomer) for a tire, there is, among other things, the problem of balancing friction (traction) and tread wear resistance.
Besides the very special know-how and talent required, one also needs very deep pockets and a steady, reliable source of reasonably priced oil—actually you are at the mercy of the price of a barrel of oil, which has plummeted as of late. Then you have other raw materials and/or ingredients as well as waste disposal to deal with, etc.
Over the years, many tire producers and others have tried to produce polyurethane pneumatic tires, cord reinforced or not, the Russians included.
The Austrian company LIM (Liquid Injection Molding) also tried, and ended up in receivership.
Here in the U.S., you also have Amerityre Corp., which has been at it for nearly two decades, using millions of dollars of investors' money. Amerityre has put development of a road-going urethane tire on the back burner, for now, choosing instead to develop industrial and bicycle tires.
Will we have another tire revolution? Maybe. And if and when we do, perhaps another public race should be organized.
Jacques Bajer is founder and president of Tire Systems Engineering Inc. in Grosse Pointe, Mich., a consultancy dedicated to road/tire/vehicle systems technology. The French-born engineer was an active participant in the evolution of the automotive and tire industry. His work at Ford Motor Co. from 1955 to 1970 led to the development of the tire uniformity grading machine (1962) and the low-profile tire (1964). Mr. Bajer also was a key figure in the radialization of the American market. The holder of many patents on tire production and design, his work earned him a spot in the Tire Industry Association's Hall of Fame, to which he was inducted in 2006.