Having enough air in our tires is a safety check American's just don't seem to be able to handle. Now, Michelin may take air out of the safety equation with their revolutionary new "Tweel," a combination of tire and wheel that rides on rubber permanently attached to flexible spokes fused with a flexible wheel that deforms to absorb shock. Checking tire pressure, fixing flats, highway blowouts and balancing between traction and comfort could all fade into memory-if the Tweel becomes real.
Over a hundred years ago, in the 1890s, the Michelin brothers were the first to use air-filled tires on a racecar. Almost 60 years ago, the company introduced the radial tire.
"Major revolutions in mobility may come along only once in a hundred years," said Terry Gettys, president of Michelin Americas Research and Development Center in Greenville, S.C. "But a new century has dawned and Tweel has proven its potential to transform mobility. Tweel enables us to reach levels of performance that quite simply aren't possible with today's conventional pneumatic technology." Gettys said the name Tweel was created to represent the fusion of tire and wheel. He added it is "one of the most exciting breakthroughs in tire technology in my lifetime."
At the Detroit Auto Show, Michelin showed a video with an Audi A4 running on concept auto Tweels. The Tweel doesn't look like a conventional tire, you can see through it, but it has some unconventional aspects that are drawing attention from the U.S. military. Stopping to repair flats can be dangerous for soldiers, making them vulnerable to ambushes. Landmines and other explosives can disable trucks. Preliminary tests by Michelin show that the Tweel can run over explosives and keep on rolling even if some of the spokes are broken and some tread ripped off. It also directs the blast energy of land mines and other explosives outward rather than up and into the vehicle like traditional tires.
"The Tweel automotive application, as demonstrated on the Audi, is definitely a concept, a stretch application with strong future potential," said Gettys. "Our concentration is to enter the market with lower-speed, lower-weight Tweel applications. What we learn from our early successes will be applied to Tweel for passenger cars and beyond."
Michelin has also found that it can tune Tweels so vertical stiffness (which primarily affects ride comfort) and lateral stiffness (which affects handling and cornering) can both be optimized, and enable performance not possible for current inflated tires. The Tweel prototype, demonstrated on the Audi A4, is within one percent of the fuel economy of current tires. Michelin has also increased the lateral stiffness by a factor of five, making the prototype unusually responsive.
Michelin estimates that even with the reliability of today's radials, motorists get a flat every 80,000 miles driven, which can be a nuisance if not a dangerous situation. The National Highway Traffic Safety Administration says that three out of four vehicles have at least one under-inflated tire, which can lead to blowouts, affect the load-carrying capacity of the vehicle, accelerate wear, and reduce performance of the tires. A Tweel, with the same tread depth as a conventional tire, under research conditions, seems to last twice as long. And the Tweel can be re-treaded thereby lengthening its useful life.
Michelin says that radial tire technology will continue as the standard for the foreseeable future, but lessons learned from Tweel research are being applied to improve conventional tires. The first real-world application of Michelin's Tweel is available on a wheel chair-iBOT-invented by Dean Kamen. The iBOT can climb stairs and navigate uneven terrain, offering mobility freedom impossible with traditional wheelchairs. The Segway LLC's Concept Centaur, a prototype that applies self-balancing technology to a four-wheel device, has also been equipped with Tweels to increase its performance potential.
The Tweel probably won't be in the showroom for a least a decade. If all goes well in the lab, Tweels could replace radials, but that is a long-term prediction. It took radials 30 years to replace bias tires and become the universal tire standard.