Dubbed "Energy Return Wheels," new prototype airless wheels from Colorado-based Britek Rubber and Tire could mean the end for bike pumps. An internal rubber layer is stretched taut over adjustable rods, surrounded by a series of elastic cushions (where air would typically be) and a rubber tread along the exterior. 29-inch carbon fiber rims and open sides reduce the weight of the wheels, while the inside rubber layer allows potential energy to be stored within the wheels themselves. According to Britek founder Brian Russell, the stored energy is returned and converted into forward momentum. Additionally, the rubber-tensioning rods can be adjusted to make the wheels to run harder or softer, depending on the surface condition. Check out the wheels in action in the video below.