Behold the Hankook iFlex, the auto industry's latest attempt at an airless tire. Tire companies have been trying for years to make a tire that doesn't need air. The reason is simple: Although tires are more reliable now than they've ever been, they're still totally dependent on the pressure that holds them up (even run-flat tires aren't designed go very far without air). But it's not an easy task. Tires operate in a highly stressful environment—they are not only supporting the car but also absorbing bumps, enduring wild temperature swings, and dealing with the forces from cornering, acceleration, and braking. The trick to the airless tire is finding a combination of materials that can withstand all that pounding over the course of many years and tens of thousands of miles while still offering comparable performance to a pneumatic tire. The last time a tire company tried this in a high-profile way was in 2011, when Bridgestone showed off its Airless Tire Concept. Like the Bridgestone, Hankook's iFlex combines the wheel and tire in one unit. Hankook's design has the wheel spokes extending all the way out near the edge of the tire. TThe company claims that this distributes the loads on the tire in a way that compresses the bottom but stretches the top. The construction is made from polyurethane elastics, and Hankook says that 95 percent of the tire can be recycled.