Tires of the Future?

http://www.autofieldguide.com/articles/020508.html


If automotive tire upstart Amerityre can perfect its polyurethane tires, we may soon have to revise the phrase "where the rubber meets the road." By Kermit Whitfield, Senior Associate Editor

Unlike the traditional process that builds tires in layers, Amerityre's polyurethane tire production method pours polyurethane directly into a mold spinning at 300 rpm. Centrifugal force then distributes the material evenly around the beads and belts which sit on a core in the mold, producing a monolithic structure. Two key advantages to this approach: there are no layers that can delaminate and lead to tread separation, and the tire can be made perfectly round, which reduces rolling resistance.

Rubber tires' many inherent weaknesses—tread separation, dry rot and a complicated and time-consuming production process—all argue for the development of an alternative tire material. Attempts have been made. As far back as the 1950s tire companies were experimenting with making tires out of polyurethane, but they couldn't concoct a formula that would yield performance as good as that of rubber, so they gave up. Now Amerityre (www.amerityre.com; Boulder City, NV), a small company that currently specializes in tubeless tires for bicycles, golf cars and wheelbarrows, has developed a polyurethane auto tire that it claims can go toe to toe with rubber. "Goodyear, Firestone, Pirelli and others all tried but none of them are true inventors and their chemistries were not correct," says Richard Steinke, Amerityre's president and CEO. But after 25 years spent testing polyurethane formulations, Steinke claims to have hit on the right compound. His company has produced prototype run-flat tires based this proprietary formulation that have passed the Federal Motor Vehicle Safety Standard No. 109, which is the first step toward commercialization. This has been enough to get some people in the automotive world to take notice. Lee Iaccoca has signed on as an advisor with the startling assertion: "In my 40-plus years experience in the automotive industry, Amerityre's car tire technology has the most potential to change the industry as we know it." The key word here is "potential." But as Steinke explains, polyurethane tires could enjoy some clear advantages over their traditional rubber counterparts.

Chemistry and Production. First, there's the material itself. Polyurethane is a fully reacted polymer in which every molecule bonds with another so it is chemically inert, which keeps it from oxidizing or leaching chemicals, theoretically extending tire life. With rubber, unbonded elements are left over from the vulcanization process that continue to react as the tire ages, leading to hardening, cracks and more frequent trips to the tire store. Then there is the cost of production. Making rubber tires is a complex undertaking requiring expensive equipment like banbury mixers, calendars, extruders and vulcanization presses, and because of the lengthy vulcanization process cycle times can be 30 to 40 minutes. Steinke says his proprietary manufacturing process eliminates all of that in favor of a simple spin-casting operation that can produce a new tire every three minutes. He estimates total investment in a plant that can make over a million tires a year at about $5 million, or less than 10% of a traditional tire plant with a similar capacity. Assuming raw material costs are roughly similar, Amerityre would clearly have much lower production costs.

Performance. But even cheap polyurethane tires won't sell if they don't perform as well as rubber. Prototype polyurethane tires of the distant past ran into not-so-niggling problems during real-world testing such as poor wet traction and melt down during braking. But Steinke says his formulation has gone head-to-head in track tests against top-of-the-line run flat rubber tires and met or exceeded their performance numbers. In fact, in the key metric of rolling resistance he claims his tire is 45% better than the competitive test tire, leading him to estimate that a car equipped with polyurethane tires could get up to 10% better fuel economy. According to Steinke, figures like those have drawn the attention of at least three unnamed automakers interested in the technology, one of which is already testing prototypes.