A battery-powered derailleur by Shimano promises to bring ease and accuracy to changing gears by enabling riders to shift with a light touch to two electronic switches. The Dura-Ace Di2 7970, is being used by three professional teams competing in the Tour of California: Columbia High Road, Garmin Slipstream and Rabobank. A full set of components with electronic gears will cost about $1,250 more than the newest mechanical version, which sells for about $2,750. ($4000 total!) Upgrading an existing Shimano system is expected to cost about $2,200. The system will fit onto nearly all racing bicycles. Two paddle-shaped electronic switches that sit behind the brake lever allow riders to shift gears. Tapping either paddle lightly in Di2 sends an electronic signal through a wire to a small motor inside the derailleur, moving the body and thus the chain by turning a worm gear. The biggest innovation is with the electronic front derailleur which is able to make constant readjustments to reflect changes in the chain’s position caused by shifting with the more frequently used rear derailleur.
More at the New York Times
