Shimano Di2 electronic shifting on a da Vinci Tandem
Di2 on a tandem is absolutely amazing, as long as you can get the range of gear you need. We have a real advantage here. At the time this was written, the only Di2 triple available is a Shimano XTR and only work with chainring that are way too small for a traditional road tandem. Our drivetrain and little chainrings work perfectly with the XTR Di2 triple front derailleur. We build our Di2 bikes with the 11 rear cassette range of your choice and three chainrings equivalent to 26, 42, 58 tooth (physically 13, 21, 29 tooth). You can shift the front derailleur under a load as easily as the rear.
Another great feature of the Di2 is the digital display unit. This bike-computer sized display shows what front and rear gear you are in, shifting mode, battery level, and provides a convenient place to charge the battery. The battery last very long and most teams might only need to charge it once or twice a season.
The Synchro shifting is working incredibly as well. Imagine going through all the best usable gears with just a touch of the button with your right hand. When you need a front shift, the system automatically shifts the rear to give you a smooth and consistent gap.
Gear range examples
11-40 cassette, 13-21-29 chainrings, 700c wheels = 17.5 to 142.5 gear inches.
11-36 cassette still has a 19.5 to 142.5 gear inch range.
There are option to use smaller left side freewheels and drop the gear range even lower.
We just shipped a Symbiosis full suspension tandem with 650b (27.5″) wheels 19 tooth freewheels and that tandems had a 16 to 130 gear inch range.