Michelin Debuts Tire that Operates Without Air
DETROIT — At the North American International Auto Show (NAIAS) on January 9, Michelin showcased a potential future for mobility, an integrated tire and wheel combination missing one ingredient normally considered vital for traditional tire performance – air. The company unveiled the first real-world fitments for its “Tweel” — which operates entirely without air. Michelin's Tweel is in production and available as an enhancement for future iBOT mobility systems. Invented by Dean Kamen, the iBOT mobility device has the ability to climb stairs and navigate uneven terrain, offering mobility freedom impossible with traditional wheelchairs. Additionally, Segway LLC's Concept Centaur, a prototype that applies self-balancing technology to a four-wheel device, has also been equipped with Tweel to increase its performance potential.Beyond these first real-world applications, Michelin has additional projects for Tweel on construction skidsteers and a variety of military vehicles. The most intriguing application may be Michelin's early prototype Tweel fitment for passenger cars. The mobility company released video of promising Tweel performance on an Audi A4.The heart of Tweel innovation is its simple looking hub and spoke design that replaces the need for air pressure while delivering performance previously only available from pneumatic tires. Flexible spokes are fused with a flexible wheel that deforms to absorb shock and rebound with ease. Without the air needed by conventional tires, Tweel still delivers pneumatic-like performance in weight-carrying capacity, ride comfort, and the ability to “envelope” road hazards. Michelin has also found that it can tune Tweel performances independently of each other, a significant change from conventional tires. This means that vertical stiffness (which primarily affects ride comfort) and lateral stiffness (which affects handling and cornering) can both be optimized, pushing the performance envelope in these applications and enabling performance not possible for current inflated tires. The Tweel prototype, demonstrated on the Audi A4, is within 5 percent of the rolling resistance and mass levels of current pneumatic tires. That translates to within 1 percent of the fuel economy of the OE fitment. Additionally, Michelin has increased the lateral stiffness by a factor of five, making the prototype unusually responsive in its handling.