Tretta AWD Bicycles put that lazy front wheel to work
Although they’re very seldom seen, 2-wheel drive bicycles have existed in one form or another almost as long as their traditional rear-wheel-drive counterparts. While most of them have been one-off experiments or short-run production models, Japanese bicycle manufacturer Arte Co Ltd has decided to give the 2WD thing a shot nonetheless, with its Tretta AWD Bicycle line-up.
Tretta AWD bikes have been available in Japan since the beginning of the year, but just made their U.S. debut this September at the Interbike trade show in Las Vegas. While there are no immediate plans for North American availability, the Interbike appearance was aimed at gauging stateside receptivity to the rather unusual bicycles.
Pedaling power is delivered to the rear wheel using the usual right-hand-side crankset/chain/cassette arrangement. On the non-drive side of the rear hub, however, is a cog that drives quite a long chain. That chain stretches from the rear hub up to a set of small cogs located near the top of the down tube.
A much shorter chain goes from those cogs to yet another cog, mounted on an arm that extends from the head tube. A flexible universal joint connects that cog to another one, that is mounted on an arm that is attached to (and that turns with) the front fork. Finally, a third chain extends from the cogs/universal joint down to a drive cog on the front wheel hub.
It’s a set-up that’s difficult to describe, and that Arte unfortunately hasn’t provided any close-ups of, but it’s what allows the system to work even when the front wheel is turned to one side.
The Tretta bikes were initially designed to provide Japanese commuters with increased traction in adverse weather such as snow and rain, although the applications for mountain biking are pretty obvious, too. Unfortunately, all those extra chains and cogs add to the bike’s weight and will require more maintenance, plus they can’t be used with a suspension fork.
It also looks like that one long chain could rub against the inside of the rider’s leg – that problem and other limitations may be addressed in future versions of the bikes, according to a representative from the company.
Tretta buyers in Japan can currently choose between mountain, cyclocross, beach and city models. They range in price from ¥33,000 to ¥75,000 (about US$402 to $912).
Source: Tretta (Google translated from Japanese)