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Bike Uses Ball Bearings, Not Gears, To Shift

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With a simple twist of the wrist, the promotional materials read, you can shift this bike in a way that’s “as easy as adjusting the volume on a radio.”

As bike-industry marketing speak goes, the “radio” analogy was about as weird as I’d seen. But this month, while riding a $950 bike new from Jamis called the Commuter 4, I could see the connection.

Jamis city bike does not have gears

The shifting on this city bike does not involve traditional gears. Instead, something called the NuVinci N360 transmission adds and subtracts resistance as you pedal for power and speed.

As the company explains it, the NuVinci N360, which is made by Fallbrook Technologies, is neither a derailleur system nor an internally-geared drivetrain. It is a unique system that uses a set of large ball bearings inside a rear-wheel hub.

X-ray view: NuVinci hub uses ball bearings, not gears, to affect power and speed

No gear cassette is required to “change gears.” Instead the internal bearings rotate off each other in various configurations as you turn a shift knob on the handlebars to give a range of pedal power.

It sounds strange. But in use the NuVinci system is about as easy as adjusting the aforementioned radio dial. On the handlebars of bikes like the Jamis, you control the transmission with a rubbery grip — twist one way for more power, or twist back to “downshift” into an easier setting for a hill.

Rear hub area is a NuVinci “transmission”

There is no clicking or ratcheting of gears. The shifting is seamless and micro-adjustable — you can dial in an exact amount of resistance for the road ahead, be it flat, inclined, or going down.

A huge range of represented gearing comes with the NuVinci N360. At the high end the range is equivalent to about a 50-tooth chainring up front and a 12-tooth cog on back. That setup is powerful enough to blast to 30mph on flat land if you can push the resistance.

Further intrigue: To reveal your transmission setting, a small animated icon of a cyclist on a hill sits in a display window near the shifter. You glance down at the little cyclist to see how steep his animated hill is, and that corresponds with the NuVinci system’s setting.

Grip-shift mechanism has cartoon icon to represent shift level in NuVinci hub

Overall, the transmission setup takes some getting used to. For people who have always pedaled with gears, the “infinite adjustment” of the NuVinci system can be odd. It’s touchy, too: A subtle twist of the shift grip can dramatically change resistance from too easy to too hard.

I am not ditching my regular gears anytime soon, especially on my race bikes. The NuVinci is a heavy hub and not ideal for the rigors of off-road riding. But for a city bike like the Jamis it is an interesting and low-fuss option. “As easy as a radio dial.” I can see that now.

—Stephen Regenold is founder and editor of www.gearjunkie.com.

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