Flat tyres have always been an inextricable part of riding — even without the occasional road hazard, tyres lose pressure as air diffuses through the sidewall, requiring routine re-inflation. But, one San Francisco start-up has a plan to eliminate all that extraneous pumping with the PumpTire.
The PumpTire consists of an inner tube, the tyre itself, and a special uni-directional air valve that screws into the stem of the inner tube. When the pump is active, it uses the tyre's rolling motion to draw in air from the atmosphere, through the one-way valve and into a lumen that runs along the outer edge of the tyre. As the tyre rolls, it squishes the lumen flat, forcing air into the main tube and when the weight of the tyre is removed, the lumen re-inflates before it's rolled over again. The system automatically shuts the valve when the desired pressure is reached. The doesn't require any special modifications or rims.
The PumpTire comes in two varieties; the City Pro — a high performance 700c x 28mm tyre with a max 100psi, and the City Cruiser— a 26 x 1.5 inch tyre with a maximum 65 psi. They are a Kickstarter project, so there's no guarantee these will see actual pavement time, and they are still a ways from their $US250,000 goal with 40 days to go. [kickstarter]