Triathlete’s Complete Guide to Electronic Shifting

For triathletes, the widespread availability of electronic shifting has not only increased the speed, accuracy, and consistency of shifts, but it’s also led to a huge change in the way tri bikes are designed. By breaking the bonds of shift cables and derailleur housing, brands are now able to create frames focused only on aerodynamics and performance, as wires (or wireless systems) allow for greater freedom. This has some triathletes weighing electronic shifting against mechanical shifting when it comes to their bike setup.

But like everything, that freedom comes with a cost (and no, we’re not talking about simply the cost of the components themselves). If you have electronic shifting, are considering electronic shifting, or ever think you might want electronic shifting, read our extensive guide below to help decode the complex world of electronic shifting brands, levels, component compatibility, and more.

A (brief) history of electronic shifting on bikes

The first commercially successful electronic bicycle drivetrain was created by Shimano and available to consumers in 2009. Shimano named this system Digital Integrated Intelligence or Di2. Craig Alexander actually won his first Ironman word title in 2008 using this new Di2 electronic shifting on his bike. It didn’t take long for rapid adoption to occur and consumers were flocking to the Di2 groupsets for ease of use and impeccable shifting performance.

One of the primary benefits for triathletes using the new electronic shifting was the ability to locate shifters on both the bullhorn brake levers and the tip of the aerobar extensions. This meant triathletes could now shift while out of the aerobars just as easily as in the aerobars.

Campagnolo was next to the electronic shifting party when they introduced Electronic Power Shift (EPS) in 2011. While Campy failed to gain mainstream adoption, they did offer three ranges of electronic systems as early as 2012—the same year Shimano introduced electronic shifting into their more budget-friendly Ultegra lineup.

It wasn’t until 2016 that SRAM finally launched their first competitive electronic drivetrain with a wireless electronic transmission. The Shimano and Campy offerings both relied on wires running through the frame (or often taped to the outside of the frame in the early days) to connect the battery to the shifters and derailleurs. This new offering from SRAM promised a reprieve for mechanics and consumers who were overly burdened with trying to troubleshoot and diagnose problems with cable routing and damaged cables inside of frames on Shimano and Campy counterparts.

This new wireless groupset system was called SRAM eTap and it used bluetooth low-energy signals to control the derailleurs which each had external removable batteries mounted directly to them. The new SRAM system was wonderfully wireless, but the first generation had many bugs and wasn’t as reliable as the Shimano system which had already been proven in seven years of racing.

SRAM’s early electronic shifting struggles were soon repaired when they launched the SRAM eTap AXS system in 2019. This new system from SRAM had better shift quality, more reliable operation, and better ease of use. Shimano introduced a “wired less” system in 2021 that included road shift levers that used wireless communication to control the derailleurs, but still required wires to connect the derailleurs to the large internally stored battery. The Shimano 12-speed electronic groupset has mandatory backwards compatibility with select 11-speed bar-end shifters and brake-lever shifters.  In 2023 Campy joined the wireless movement with the introduction of their first wireless groupset, Super Record Wireless (though it’s not yet available for triathlon).

Today we have mass-adopted electronic groupsets from Campagnolo, Shimano, and SRAM, read on for a look at how the systems operate and the benefits and disadvantages of each system compared to good, old-fashioned mechanical shifting.

Triathlete’s Complete Guide to Electronic Shifting: How does it work?

The mechanical derailleur existed for over 100 years before Shimano launched the Di2 electronic derailleur. Why did it take so long? The mechanical derailleur is simple and efficient, and it uses a mechanical control lever, attached to a cable that puts tension on a spring loaded pulley system to change the gears on a bicycle.

An electronic rear derailleur is much more complicated, but accomplishes the same end result of shifting the gears on a bicycle. In an electronic system, digital system switches are used to relay signals to the derailleur servo motor (something a mechanical shifter doesn’t have) which is powered by a battery (internal or external) and uses worm gears to conduct a shift. The system switches are a nice addition to the electronic shifting because they allow for multiple locations for shifters and don’t depend on a clean cable routing path like mechanical systems—allowing for more freedom of frame design and less legwork when installing new cables/housing.

The front derailleur shifting performance massively improved with the addition of electronic shifting. Front derailleurs are very complicated because they must shift a  chain (under a lot of tension) a very large vertical distance between the chainrings attached to your crankset. Mechanical front derailleurs are also prone to rub on the chain, causing added drivetrain friction when the rider cross-chains (a term describing when your chain is stretched across the inside and outside cogs).

The computer-controlled accuracy of an electronic front derailleur means the system shifts much more precisely, with a faster and more powerful force. The electronic front derailleur also auto-trims to prevent the chain from rubbing on the derailleur when it gets to the outer gears in either direction.

Triathlete’s Complete Guide to Electronic Shifting: Why electronic shifting?

Electronic shifting, particularly for triathletes, is a huge boon. No other shifting system allows the rider to change gears while in either the aerobars or on the basebars. SRAM’s wireless system even allows you to put shifter buttons in any position you’d like—regardless of location to the brake levers or bars.

In a sport like tri, where the goal is to increase comfort and focus on the bike, electronic shifting is also beneficial because it requires less physical effort to complete a single shift—find your position on the bike, put out your power, and simply touch a button to change gears as the terrain changes. Similarly, an electronic brain automatically executes precise shifts and adjusts the other derailleur based on position. There’s no need to trim the position of a derailleur due to cable stretch or other considerations. This level of precise shifting also leads to better longevity for drivetrain parts and reduced friction that can create wasted watts.

Triathlete’s Complete Guide to Electronic Shifting: Why not electronic shifting?

Obviously cost is a major consideration when it comes to upgrading to electronic shifting, as many systems cost nearly three times their mechanical equivalent. Though prices have come down substantially in the last few years, the least expensive wired option is Shimano’s 11-speed  Di2 105 R7150 that runs around $1500, as its mechanical counterpart can be found for under $700. SRAM’s wireless 2×12-speed Rival eTap AXS system is also in the $1500 range, while its mechanical equivalent is under $1,000.

Cost aside, there is an argument to be made for the outright reliability of a shifting system that has no batteries to charge nor wires that could be snipped, pinched, or disconnected (while rare, wireless communication issues can surface as well). Same goes for software glitches or firmware bugs that are next-to-impossible to diagnose on your own. Finally, there’s the issue of weight, as systematically mechanical setups are lighter than electronic ones, but of course those differences are marginal and effectively inconsequential for triathletes.

To upgrade your bike to electronic shifting, you need:

1. Electronic derailleur(s)
2. Battery
3. Shift switches (bar end or bullhorn buttons)
4. Battery charging device

If you’re using Shimano’s “wired less” system or Campy’s EPS you will also need internal wires to connect the internal battery to the derailleurs and more wires and junction boxes to connect the shift switches to the battery. SRAM and Campy’s (newest non-triathlon compatible) systems are both wireless so the component list is shorter and simpler.

Read below for our guide to each brand’s offerings and compatibility charts.

Triathlete’s Complete Guide to Electronic Shifting: SRAM

SRAM eTAP AXS

The SRAM eTAP AXS system is available in four distinct, yet interchangeable, lines. All of the SRAM AXS systems are wireless using Bluetooth Low Energy signal transmissions for shifting. At the core of the SRAM 12-speed lineup is the Flattop Chain and the cassettes that use the SRAM XD-R standard, allowing for the small cog to have 10 teeth. The lower tooth count on the small cog allows for equivalent gearing ratios with much smaller chainrings up front. For example, a 55T chainring with an 11T cog is equivalent to a 50T chainring with a 10T cog.

Since the SRAM AXS systems are wireless, each derailleur and shift button must be connected to a battery for power. The derailleurs (front and rear) use the same standard and detachable rechargeable battery—SRAM makes battery charging cradles for these removable batteries.

The shifters either gather their power from non-replaceable batteries like the Wireless Blips, use a replaceable coin cell battery (like Zipp Vuka AXS Shift Extensions), or plug into the Blip Box (which also has a coin cell battery). (Recently SRAM released an update that effectively obsoletes the Blip Box for triathlon use.)

None of the brake lever options from SRAM have integrated shift buttons, and while there are many options available for remote shifters, they are not all compatible with every system. The Wireless Blips ($100 per pair) work with any rear or front derailleur for triathlon and require a smartphone. The Wireless Blips have a non-replaceable battery and a warranty of two years (after which time you will need to discard and purchase new ones).

If you choose to use a Blip Box you can then select the wired buttons in Blips, Clics, or Multi Clics depending your preference for button shape and location. The last option is to use the Zipp Vuka AXS Shift aerobar extensions which have a port for wired shift buttons and a coin cell battery to power the shifting.

SRAM Apex

The entry-level Apex groupset does not have a front derailleur option and is only available in 1x options with large-range cassettes of 10-36 or 10-44. The default Apex cassette is an 11-44 that uses the Shimano HG freehub body making it compatible with more wheelsets but often requiring larger chainrings. Apex also works with all the SRAM AXS drivetrain components including batteries, shifters, brake levers, chainrings, and chains.

SRAM Rival

The second-tier groupset from SRAM has two levels of rear derailleurs: The Rival AXS XPLR rear derailleur is only 1x compatible, while the standard Rival AXS rear derailleur works both as a 1x or a 2x system (with a front derailleur).

SRAM Force

The race-ready Force AXS groupset also comes in both the standard or XPLR rear derailleur options but sees the weight of the components drop significantly, as the speed of shifts increases.

SRAM Red

The top-of-the-line Red AXS groupset nearly doubles in price from the Force lineup and includes nice upgrades like ceramic-bearing pulley wheels in the rear derailleur. The Red lineup also has the standard or XPLR series rear derailleurs and offers the lightest components and fastest shifting speeds from SRAM.

Triathlete’s Complete Guide to Electronic Shifting: Shimano

Shimano Di2

Shimano Di2 offers three lines of their latest 12-speed electronic shifting groupsets for triathlon. While each line works for triathlon, they require you to use old 11-speed brake levers, bar end shifters, and cables. You must also first update the firmware on the brake levers and bar end shifters and then use a small adapter plug to transition the older 11-speed wiring to the newer 12-speed wiring.

While triathlon use may seem like a bit of an afterthought in the latest 12-speed electronic groupsets from Shimano, there is a viable solution to have a functioning groupset. Shimano uses one larger battery that powers both derailleurs and is stored inside the frame and connected to the derailleurs via cables. This large Shimano battery lasts for several months of regular riding on a single charge, and because the system is wired there is no other power required for shifting. Since the Shimano battery is located inside the frame, charging of the battery is accomplished using a USB cable that attaches to the rear derailleur.

Shimano 105

Shimano’s newest budget-friendly Di2 wireless shifting groupset, 105, uses all the same components and features of the flagship Dura Ace groupset but in a slightly heavier and slower form factor. Shimano 105 offers the legendary Shimano electronic shift performance and front derailleur auto trim at a budget price. While there are no dedicated bar end shifters or brake levers for the 105 line, the Ultegra and Dura Ace components are plug-and-play compatible with 105 derailleurs.

Shimano Ultegra

Shimano Ultegra stands for value and race proven performance. While slightly heavier and more sluggish than the premium Dura Ace, the Ultegra lineup offers a nice improvement over the 105 line while still maintaining the essence of Di2. There are Ultegra brake levers that work with 12-speed derailleurs, but only with mechanical cables and not with full hydraulic cables. The brake levers can still be used with disc brake bikes with the use of mechanical or hybrid hydraulic disc brake calipers. These mechanical levers can of course also be used with traditional rim brake bicycles as well.

Shimano Dura Ace

Dura Ace Di2 has always been considered the gold standard for electronic shift performance. It is the standard the competitors use to judge their performance. The Dura Ace lineup still uses the 11-speed brake levers, bar-end shifters, and electronic wires for the cockpit electronics. The Dura Ace brake levers ST-9180 are fully hydraulic and include shift buttons. These levers are not sold with disc brake calipers, making the hydraulic Dura Ace shifting and braking system the most expensive braking system by far.

Triathlete’s Complete Guide to Electronic Shifting: Campagnolo

Campagnolo does have a new fully wireless electronic drivetrain but it is not available for triathlon. However, they do offer a wired electronic groupset in the Super Record EPS.

Similar to the Shimano Di2 system, the Campy EPS system uses a large internal battery that is attached via electronic wires to the derailleurs and shift buttons. There is currently no offering for hydraulic disc brake shifting, but the mechanical cable brake lever can be used with either mechanical or hybrid hydraulic disc brake calipers, just like the Shimano Ultegra levers.

The Campy system is 12 speed and all of the shifters, brake levers, and derailleurs use the same standard of electronic wires. The Campy EPS requires a control box “brain” somewhat similar to the SRAM Blip Box to control the shifting. While the Campy electronic drivetrains have failed to gain mass acceptance, they have proven innovative and performance capable.

Electronic Shifting Comparison Chart: SRAM vs. Shimano vs. Campagnolo

* Mechanical brakes only

** Hydraulic brakes only