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See Inside December 2005

Easy Rider

Automatic transmission makes cycling a breeze
FREEWHEELING:



JOHNNY JOHNSON
There are two kinds of cyclists in Manhattan: the quick and the dead. This narrow island between the Hudson and East rivers is possibly the least bicycle-friendly place on the planet. Delivery people, couriers and casual cyclists face the challenge of crossing six-lane avenues choked with heavy trucks and honking taxis. And even if you make it to the oasis of Central Park, you must contend with packs of riders on high-end racing bikes who seem to be engaged in a perpetual Tour de France.

As a mild-mannered graduate student from California who was spending the summer in New York City, I sensed that I needed some high-tech edge to compete in this torrent of two-wheeled traffic. I soon learned that Shimano, the Japanese manufacturer of bicycle components, produces the ultimate accessory for recreational cyclists: a digitally controlled automatic transmission that takes all the guesswork out of gearshifting. I called up Shimano's U.S. headquarters in Irvine, Calif., and convinced the company to let me evaluate this voguish velocipede for Scientific American.

Just to be clear, I don't have an aversion to hard pedaling. On the West Coast I use my bike to commute to school and cart my groceries. I don't own a car and have no use for a moped or scooter. Bicycling is how I get my exercise. But even as a bike-lane veteran, I'm often stymied by the gearing on a standard bicycle. Take my commuter ride, for example, a hybrid road/mountain model made by Specialized Bicycle Components. It has three chain rings--small, medium and large--bolted to the pedals; working with the bike chain, each of these toothed rings can drive one of seven sprockets on the hub of the rear wheel. In theory, that gives me 21 gears to choose from. The problem is that some of those 21 configurations are redundant. For example, pairing the biggest front chain ring with one of the larger rear sprockets delivers the same gear ratio as combining the smallest chain ring with one of the smaller sprockets.

Furthermore, the chain is stretched diagonally in some gear combinations, which can wear down the chain links or tear the teeth off the sprockets. In reality, I get only about seven gears out of my bike--and a bit of a headache from trying to figure out the proper pairings. Often I find myself in the wrong gear, which is bad for the bike and terrible on the knees. Legs have an optimum rate for going around in circles; ideally, you should be cranking the pedals at about 90 revolutions per minute.

The solution for cars is an automatic transmission, which shifts the vehicle's gears so that the engine can hum along in its own preferred range (2,000 to 3,000 rpm) no matter what the car's speed. Not surprisingly, automatic transmissions for bicycles have been in development for more than 30 years. The largest market for the most up-to-date models is Europe. Jasen Thorpe, consumer marketing manager for Shimano's American division, notes that in the U.S., "We have our Lance Armstrongs and Greg LeMonds," but the Europeans are more likely to rely on bicycles for their everyday needs.

In the U.S., Shimano is after the leisure market. Racing cyclists want complete control over acceleration, but the typical weekend rider will often take convenience over performance. The bicycle that Shimano sent me was a Bianchi Milano, an Italian model with a somewhat retro look. It was equipped with a seven-speed Nexus internal hub, a transmission system that looked like an oversize beer can enclosing the bike's rear axle. No shift levers were on the handlebars; instead the gears were selected by Shimano's Digitally Integrated Intelligence (Di2) system, which was controlled by a computer chip in a gray, molded-plastic enclosure mounted on the bike frame.

"Take this bike to the coffee shop," Thorpe suggested. Appropriately, the Bianchi Milano sported a decal of a cappuccino cup with the words "Caf¿ Racer." I cruised down the bike path paralleling Manhattan's waterfront, admiring the variety of refuse floating between the piers. I was impressed with how smooth and reliable the automatic transmission was. One of my concerns had been that I would have to cross a busy street starting from a dead stop and that the bike would leave me stranded in high gear and heaving wild-eyed on the pedals as a yellow cab careered toward me. But no--every time I came to a stop, the transmission would start from the lowest gear. As I accelerated, it geared up as naturally as I would have done myself. There were no alarming clunks as the gears shifted, either.

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