If an Electric Bike Is Ever Going to Hit It Big in the U.S., It's This One

CAMBRIDGE, Mass.—On a sunny but brisk spring morning near the Charles River in Cambridge, I took a test ride on the bicycle of the future. No rockets or lasers (alas), the bicycle of the future looks pretty much like the bicycle of the present. But with the first pumps of my feet on the pedals, I felt the difference. The bike wasn't just moving, it was pushing, adding extra propulsion to my own pedaling, giving me a boost with every revolution of the pedals. Faster than expected, I reached the end of a quiet block leaning into a corner. I took a straightaway for a few blocks and pushed 20 miles an hour without hardly trying. My feet were putting out a solid paper-route effort, but the bike had me racing in the Tour de France.

The bike I tested was equipped with the Copenhagen Wheel, an electric pedal-assist motor fully contained in the oversized red hub of an otherwise normal back bicycle wheel. Inside that red hub is a delicately crammed array of computing equipment, sensors, and a three-phase brushless direct current electric motor that can feel the torque of my pedaling and add appropriately scaled assistance.