The prototype is made of an aluminum alloy frame and has 26-inch wheels. (SadaBike)

A little over two decades ago, Franco Sbarro, the famous Swiss sports car designer, took a stab at reinventing the wheel. His orbital or “hub-less” wheel, would allow for a lower center of gravity, which in theory would translate to better road grip, braking and steering.

Sadly, since then, efforts to incorporate hub-less wheels into a commercial motor vehicle have mostly stalled. Engineers have yet to figure out how to adapt the somewhat fringe idea to a car’s standard drivetrain, suspension and braking systems. Another prohibitive factor is the high degree of precision required to manufacture such a system (not to mention the exorbitant production costs).

(SadaBike) (SadaBike)

Recently, there’s been a resurgence in the concept, as a handful of inventors have begun applying it to bicycles, mainly to enhance aesthetics. Italian designer Gianluca Sada, however, has an entirely practical reason for going hub-less. Without spokes, the foldable Sadabike prototype, which sports an aluminum alloy frame and 26-inch wheels, is claimed to offer ultimate portability without compromising ride quality.

To fold it into the compact position, simply remove the wheels and push forward on the seat until it collapses into a configuration that’s comparable in size to a tote-able umbrella. The hub-less wheels and frame can also be inserted within the lining of a custom-made elastic bag, where it forms a rigid backbone sturdy enough to hold contents such as school books or a laptop. Sada, in an e-mail that was translated, described his approach to coming up with the design:

“There have been numerous efforts to produce an ideal folding bike, with a lot of focus put on reducing the weight and size, which have led to designs that are too small. That’s because to get this kind of portability, they sacrifice stability,” Sada wrote. “The compromise then is that problems with the rider’s position and comfort is further exacerbated by the tiny wheels and changing terrain. I wanted to create something that was a solution that allows for both portability and functionality of transport.”

The advantage of foldable bikes is that city officials tend to be more lenient in allowing passengers to bring them inside buses and subways. They can also be loaded aboard planes as check-in luggage.

To be clear, the Sadabike isn’t the most compact folding bicycle. That title is being claimed by the Kwiggle Bike, which debuted in August at Eurobike, an annual industry showcase held in Friedrichshafen, Germany. It folds down to a configuration that measures 19 x 15 x 9 inches, though the wheels are only 8 inches in diameter.

It remains to be seen whether the Sadabike can actually hold up to day-to-day use in challenging urban environments. The official Web site for the prototype posts only a handful of photos plus a promo video where the inventor demonstrates the ease in which the bike can be ridden on a sidewalk, folded up and carried into a building. The actual folding process isn’t shown, however.

The lack of testable data has led critics to question whether the Sadabike is even close to being a commercially viable product. MSN’s Innovation editor Rob Clymo, for instance, speculates that the rims would have to be “strengthened to compensate for the lack of spokes,” which would consequently make the wheels heavier. Over at the design blog Core77, Kat Baumann lay out her case for why, in this particular case, the implementation of hub-less wheels can be problematic:

As with most hub-less designs, its durability and usability aren’t easy to predict. Normally, if by eliminating the hub you are adding friction or resistance, complex proprietary parts, great expense or weight … you’re probably not striking gold. Without the distributed load allowed by spokes, you’re either dealing with a rigid mag-wheel (yeah, remember those? Comfy, huh?) or, as in the case of the Sada, a super vulnerable rubberized metal hoop. Hit a pothole with your proprietary rim and then come tell me about its efficiency.

Still, Sada seems undeterred. He’s currently looking for investors to help bring it to market at an estimated retail price of 1,500 Euros.