The electronic shifting in road cycling is here to stay. Its greater comfort and precision when shifting, avoiding cable tension problems and looseness of mechanical shifting, and its customization possibilities, are arguments that are increasingly convincing even the most experienced cyclists. In addition, in recent years, more affordable groupsets have emerged, inheriting much of the technology from high-end groups to make the product more accessible to a greater number of cyclists. This is the case with Shimano Ultegra Di2 or SRAM Force eTAP AXS. The major component brands, such as Shimano, SRAM, or Campagnolo, already have their own electronic shifting groupsets. But without a doubt, Shimano, a pioneer in this segment with the Di2, and SRAM, with the wireless eTAP group, are market leaders. That’s why we are going to analyze and compare their electronic shifting technologies to help you decide between one or the other.
Shimano Di2: features, advantages and disadvantages
2017/02/Bater%C3%ADa-Shimano.jpg"> We begin with the pioneering electronic shifting group, the Shimano Di2. It began to be marketed in 2009 and over the years has been perfected to better suit the most demanding cyclists, whether professional or not. It currently has specific versions for high-end or mid-high range groups for both road and cyclocross (Dura-Ace and Ultegra), as well as mountain bike (XTR and Deore XT). On the road, the only available gear option is 2x11. These are its key components:
Battery
The Shimano Di2 battery is the power source for the entire electronic transmission, responsible for powering the motors of both derailleurs. Cylindrical and elongated in shape, it is lithium-ion. It can also be installed inside the frame (although there are also specific mounts for external installation), generally inside the seatpost, which must be compatible, or the seat tube. The battery life of the Shimano Di2 electronic shifting with a single charge is approximately 1,600 km.
Junction Box
The junction box is the heart of the Shimano Di2 shifting. It is a small device, no more than 5 cm and 10 g in weight, through which the shifting cables pass to the derailleurs. It is usually installed under the stem with a mount. The device has a battery level indicator light and a small button to configure the different shifting modes, from manual to Syncro-Shift (semi-automatic shifting).
Shifters
The Shimano Di2 shifters resemble the levers of mechanical shifters. They are integrated into the brake lever and their actuation system is much simpler and more intuitive than mechanical ones. By gently pressing the button to shift up the cog or chainring, the one closest to the lever, or the down button, closer to the rider, the corresponding derailleur is activated almost instantly. This guarantees quick and precise gear changes. In this video from Velotique you can see how to use the shifters with Syncro Shift mode activated
Derailleurs
Both the front and rear derailleurs of the Di2 electronic shifting system are activated by a small integrated motor housed under a casing, which protects it from water, dust, or mud. This ensures you can continue shifting without any problems in the rain or other adverse weather conditions.
Software
The Shimano Di2 control unit can be connected to the Shimano E-Tube Project app via Bluetooth. The app is free and compatible with PC, Android phones, iPhone, and tablets. With the E-Tube app software, you can customize the electronic shifting, such as swapping the function of the left shifter for the right one or between the buttons themselves. You can also adjust the shifting speed to your needs or check information on each component and view tutorials.
Conclusions about the Shimano Di2 electronic shifting
Among its advantages, the Shimano Di2 stands out for its reliability, its easy customization capabilities, and the option for semi-automatic shifting (Syncro Shift). As for its disadvantages, we highlight that it has a more complex installation, includes cables, and is heavier than the SRAM eTAP.
SRAM eTAP: features, advantages and disadvantages
2020/01/Desviador-SRAM-Red-eTap.jpg"> The SRAM eTAP arrived on the market in 2015, six years after the Shimano Di2, revolutionizing the concept of bicycle transmission by eliminating cables. Thus was born the first wireless transmission group in history, packed with technology to ensure precise shifting, but at the same time easy to install and use for the cyclist. The first generation of the group used a protocol called AIREA for data transfer between the shifter and the derailleur. This technology encrypted all data to prevent hacking and ensured that only the cyclist had control over the shifting. But SRAM had an ace up its sleeve that it developed in secret over the next four years, called AXS, the new generation of the brand's wireless electronic shifting. AXS, introduced to the market in 2019, offers greater precision and speed in shifting, and integration and connectivity with all the bike's components, not just the transmission, but also the power meter (the new Quarq Dzero from SRAM). At the same time, a new, slightly less elite transmission group emerged to compete in the market with the Shimano Ultegra Di2, the SRAM Force eTAP AXS, with the same wireless technology as the SRAM Red. These are the key components of the current SRAM eTAP AXS:
Shifters
On the electronic shifters of SRAM, the shifting configuration is different from Shimano Di2. The shifter is a small button integrated into each of the brake levers. The left one shifts up the cassette, while the right one shifts down. To change the chainring, both are pressed at the same time. It’s a new system that takes a bit of getting used to. But in the long run, it’s more intuitive and easier to operate, according to the brand. In addition, there are alternative shifters with cables, although they are not connected to the derailleurs, only about 2 cm in diameter, called blips. They can be installed anywhere on the handlebar. A more useful shifter for triathlon handlebars and one that Shimano has also recently included for its Di2.
Derailleurs
The eTAP AXS derailleurs have received improvements compared to the first version. The speed of chainring changes has improved and the rear derailleur integrates the innovative Orbit technology. Orbit guarantees smoother and faster cassette shifts thanks to a silicone fluid inside, which also keeps the chain stable in all its movements. Each of the derailleurs includes its own motor (sealed from water or mud) and its own battery, with about 1,000 km of autonomy and which charges in one hour. In addition, they are interchangeable. If the rear derailleur’s battery runs out, for example, you can use the front derailleur’s, thus avoiding finishing your ride on a single gear.
Single chainring
SRAM is synonymous with single chainring. They introduced it to the market almost a decade ago in mountain biking and now it is also offered for road bikes and with electronic shifting. The SRAM eTAP group is also compatible with double chainring, allowing the cyclist to choose between a 1x12 or 2x12 setup, both in the Red and Force series. [irp posts="3842" name="We analyze the gear ratios of the Rotor 1x13 group for road bikes"]
Wireless system
The wireless system from SRAM is the axis around which the whole system pivots. AXS not only perfectly integrates the eTAP wireless shifting system, but also BLE, which connects the rest of the AXS components to your phone so you can customize them (power meter, dropper post for gravel or MTB), or ANT+, which transmits all the data and parameters from each training session. All of this is controlled from the AXS app, available for Android and iOS devices. In it, you can see the battery status, as well as customize the operation of the shifters, shifting speed, or schedule maintenance reminders.
Conclusions on the SRAM eTAP AXS electronic shifting
The main advantages offered by SRAM’s electronic shifting for road bikes are its easy installation, intuitive use, absence of cables, and the possibility of setting up various gearing options with single or double chainring. As for the drawbacks, it is a more expensive groupset with less battery autonomy than its rival, Shimano Di2.
Electronic shifting with or without cables, you choose
2020/12/road-cyclist-with-road-bike-1.jpg"> Electronic shifting for road cycling is no longer reserved only for competition or the wealthiest cycling enthusiasts. The launch of groupsets like the Shimano Ultegra Di2 or the SRAM Force eTAP AXS has democratized this technology, with prices that remain high but are now somewhat more affordable than a few years ago. In addition, the evolution of the transmission components themselves, which are lighter and more intuitive to use than the first generations, means that more and more cyclists are encouraged to modernize their bikes with this technology. Thus, it's your turn to choose which shifting system you prefer: the reliable and more economical Shimano Di2 or the advanced, wireless, and more elite SRAM eTAP AXS.