Is a Self-Inflating Tire Worth The Extra Cost?
Images credit PumpTire
Air is drawn from the atmosphere through the one-way valve, which protrudes from the rim like a regular valve stem. Instead of going directly into the inner tube, however, the air goes into one end of a lumen, which is a small tube running along the center of the tire [on the outside]. As the tire rolls against the ground, the lumen is compressed, forcing air out of its other end and into a second valve - this one on the inner tube. The resulting absence of air in the lumen creates a vacuum effect, drawing more air in through the first valve.
There are two versions, a city cruiser with a fixed pressure setting, and a pro version that is adjustable, from 65 to 95 PSI.
In the very clever video, you can see that it actually does work quite well. It's not cheap, at US$ 129 for the city version and $US 149 for the City Pro, but it does appear that it would keep your tires at the proper pressure. More at the company website.
This is not the first time we have seen one of these; Warren showed the Nakano Air Hub five years ago. My issue with it is that I have almost never had a low tire where I didn't have a puncture. So if you are doing serious riding, you are still going to need a repair kit and a pump handy. Or if you are an urban cyclist, you are still going to need a taxi. What do you think?