Puncture-proof tires that incorporate a flexible internal matrix instead of air are nothing new, in and of themselves. In the past several years, we’ve seen prototypes from the likes of Michelin, Amerityre, Goodyear and Bridgestone. Colorado-based Britek Tire and Rubber has also been developing something similar, known as the Energy Return Wheel. While the ERW is intended mainly for cars, the company recently released a video showing a prototype set of the wheels in use – on a mountain bike.
The automotive version of the ERW is said to not only eliminate flats, but also improve fuel efficiency and performance. Each wheel has a layer of rubber at the center, that is stretched and held taut by adjustable rods. A rubber tread is on the outside (as with a regular tire), while a series of elastic cushions occupy the space between the two – this is the area that would ordinarily be filled with air.
According to Britek founder Brian Russell, the stretching of the internal rubber layer allows elastic potential energy to be stored within the wheel. As that layer is compressed by bumps transmitted from the road, the stored energy is supposedly returned (hence the name) and converted into forward momentum. It is also said to press the tread onto the road instead of allowing it to bounce off, as is sometimes the case with pneumatic tires.
It’s an intriguing concept, but needless to say, if any engineers or physicists would like to weigh in on the matter in our comments section, we welcome your input.
The new mountain bike version of the wheels incorporate lightweight 29-inch carbon fiber rims, and (like some of the automotive prototypes) are open on the sides. Russell is wisely considering adding thin sidewalls, to keep mud and trail debris from accumulating within them.
Although there is no air pressure that riders can adjust, they can instead adjust the rubber-tensioning rods to make the wheels run harder or softer.
The mountain bike ERWs can be seen in use in the video below.