Introducing Energy Return Wheel, the world’s first airless bicycle tire. It’s essentially made from two steel hoops – one is nestled within another and suspended by a series of springs and the outer hoop has a rubber casing like a normal tire, along with an inner membrane. Its inner hoop comes with studs that attach the springs to the wheel, which can be torqued to make the tire more or less springy. Continue reading for a video and more information.
The inventor likens the dynamic of the tire to a garage door, which while very heavy, is balanced with springs to significantly reduce the energy of moving the door up and down. The outer ring of the ERW moves upwards over a bump and springs back while the inner ring stays in relatively in the same place.
This means that at cruising speed all those little bumps and vibrations in the road are absorbed and returned to the road by the tire in the form of forward momentum. A typical inflated tire simply absorbs the bumps by flexing the sidewall, creating friction, which reduces efficiency.