For years, off-road and MX riders have hassled with the inner tubes inside their spoked rims, while the vast majority of road bikes have switched over to one-piece wheels that allow a tubeless tire to be used. The reason spoked wheels are used for off-road bikes is their ability to “take a licking and keep on ticking”, to quote an oft-used saying. The spoked design allows a certain amount of flex to help absorb impacts that would crack one-piece wheels, and if the rider breaks a spoke or two he can usually continue riding – not to mention that he can repair the wheel simply by replacing the broken spokes and re-truing the wheel, rather than replacing it entirely (as would be necessary with a damaged one-piece wheel).
However, it seems that dirt riders may soon be rolling on a wheel that combines the best of both worlds – a spoked off-road design that is able to run without the use of an inner tube. Italian wheel manufacturer Alpina has been offering their “Tubeless A-System” wheels to European supermoto racers for a while now, and to coincide with the release of its enduro/MX tubeless system, the company has partnered with former World MX Champion Trampas Parker to promote and distribute their products in the USA.
How does the Tubeless A-System work? From what I can understand of Alpina’s translated-from-Italian press materials, the holes in the rim that the spokes would normally pass through are now threaded, and a small “terminal” is installed into each hole – complete with a gasket to prevent air from leaking out around the terminal. Each spoke is then connected to one of the terminals, joining the rim and the hub. The results? All the durability advantages of a standard spoked wheel, plus lighter rotating/unsprung weight and a claimed greater resistance to punctures. Even if the tire did puncture, tubeless tires tend to deflate slowly unless they have a massive hole in them, while a punctured inner tube will rapidly lose all its air pressure.
As of the last AMA Supercross race in Houston, three teams are running Alpina wheels: Butler Brothers MX, Star Racing, and Team Motoworld.com. However, all of the teams reportedly fitted their rims with tubed tires during the race, although the Motoworld.com team went tubeless in practice. So it’s clear that the teams are going to take their time testing things out before commiting to run tubeless tires, but once they’ve been proven in the crucible of professional Supercross racing, we’re sure weekend riders and maybe even the OEMs will catch on to this simple, yet innovative new product.
