Folding bicycles are wonderful, but by and large they have to strike a compromise: large wheels and limited portability, or small pack-size but with tiny little wheels. This slightly strange hubless bike promises a solution to that problem.
The Sada Bike promises standard bicycles dimensions—it uses 26-inch wheels—but its hubless design means that, as the frame folds away, it comes apart from the wheels to maximise portability. Gianluca Sada, it's designer, explains:
The wheels have no spokes, the system folds with a single movement, the packaging container can also be used as a backpack... It uses a system anchoring the wheels using smaller wheels held by a small frame and a specific quick clamping device. They allow you to fold the bike quickly and easily, using its special package like a trendy backpack.
It certainly lives up to its claims in terms of folding; check out the frame once collapsed in the image below. Obviously you have to move the wheels, too, but they're probably not particularly cumbersome given they have no hubs or spokes. They might even make a good impromptu hula hoop.
But there's one downside we can see from the off. Bicycle wheels typically get their strength from the tension in the spokes; removing them means that the strength has to be put into the rim instead. That's fine, but it adds masses of weight to the outside of the wheel—and that, if you remember your physics classes from high school, is a problem. Rotating weight is where you notice it most, because you have to get the mass spinning.
Sada doesn't really seem to address this problem—but then, perhaps given that it's a city bike, it's not a big a deal breaker as it could be. At any rate, the bicycle is still a prototype seeking, so we should perhaps hold off real criticism until we can try the finished product. [Sada]