Shimano's Di2 electronic shifting system is one of the premier component sets for road cyclists. With electronic shifting available for the Ultegra and Dura-Ace group, these professional-level components are now available for everyone, if you're willing to pay a premium price. Understanding the quirks of the Di2 system will help you optimize your performance.
What Is Electronic Shifting?
The Di2 system uses small servos in the front and rear derailleurs to shift gears. These derailleurs are controlled using an electronic signal, integrated neatly into two buttons on the shifter. The result is incredibly smooth and precise shifting under any conditions, a big jump in quality from a mechanical, cable-actuated shifting system. The brakes on a Di2 system are still mechanical dual-pivot caliper brakes, and many other components like the pedals, bottom bracket and hubs are unchanged. A battery pack can be mounted internally or externally, depending on your frame specifications.
Ultegra vs. Dura-Ace
The newer Ultegra group with Di2 integration uses most of the same technology as the Dura-Ace group. However, with slightly less efficient servos, you'll see about 30 percent less distance between battery charges. The Ultegra system uses a newer wiring system than the Dura-Ace group, and testers see little to no difference in performance between the two group sets with the exception of the shifting quality of the rear derailleur, and possibly the increase in weight of the crank set on the Ultegra system.
Using Di2 to the Fullest
Unlike riding with a traditional mechanical system, it's difficult to muck up your shifting with the Di2 system. It's safe to shift under cadence, uphill or even in a full sprint. Testers report clean and precise shifting under all conditions, even after thousands of miles of riding. Because of the intuitive controls of the Di2 shifters, you'll likely integrate the system into your riding routine seamlessly. Learning to fully take advantage of the ability to shift under heavy cadence may require you to break some old habits.
Dead Batteries and Button Issues
While critical reviews of the Di2 system are few and far between, it is possible to run out of juice or miss a shift with the buttons. Since each gear shift through the 11-speed system requires a button press, fast shifts from the top of the cassette to the bottom are still slightly slower than lever-based systems like Campagnolo's Ergo-Power system. In addition, the reliance on a battery means you could run out of juice midride. Luckily, the battery lasts for more than 1,000 miles between charges, and it charges in about an hour for 500 charges, many more than any cyclist is likely to use in his bike's life span.
- Photo Credit Thomas Northcut/Photodisc/Getty Images
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