Everything You Need To Know About Electronic Drivetrains

Upgrading or updating your bike to an electronic drivetrain is slowly becoming more affordable, and makes a lot of sense.


By Joe Lindsey |

Now that Shimano, SRAM, Campagnolo, and FSA all make electronic drivetrains, and the technology has been tested, tweaked and developed in the last decade, almost every high-end bike comes with a charging cable.

If you’re still riding a bike with mechanical shifters, you may be considering an upgrade to electronic bike shifters. All of that begs the question: Should you make the shift? (Sorry.) If you’re intrigued by electronic bike shifting, here’s what to know in advance.

Yes, you can upgrade your bike to electronic shifting.

A switch from mechanical to electronic bike shifters can involve as little as swapping four parts, says Shimano’s Road Brand Manager Nick Legan: the Di2 shifters and derailleurs (and adding the wiring harness and battery). But that’s only for current 11-speed drivetrains. Electronic shifting is controlled by firmware, but no company has released a firmware version that allows for adjusting the number of drivetrain speeds. So if your bike has older 10-speed stuff on it, you’ll need to also upgrade the crankset, cassette, and chain. (Yes, you can get by for a time with 10-speed chainrings, but the tolerances from a 10-speed ring to an 11-speed chain are so tight that it’s not recommended.)

For SRAM, similar rules apply. Neither company officially says you can mix parts but we’ll say it here: Unless you’re super finicky, a Shimano chain on a SRAM cassette or vice versa works fine with 11-speed drivetrains. It’s just a little noisier. But no part of SRAM’s AXS groups will work with any non-AXS component, since they changed the chain pitch and roller size slightly.

Electronic doesn’t always play well with older frames.

If your bike has external cable routing, you’ll have to zip-tie the wiring to the frame. It’s entirely doable technically, but the aesthetics aren’t great. As well, Shimano’s new Di2 drivetrains are based around cigar-style internal batteries, which won’t fit on all frames. Most frames made since 2012 have internal routing with cable stops that can be swapped for mechanical or electronic cables. You may have to buy new stops through a dealer.

On the other hand, SRAM’s wireless eTap provides a great retrofit option to older frames, both because you don’t have to deal with a wiring harness and because the batteries are mounted to the derailleurs. “You install the derailleurs and shifters, pair them, and you’re good to go,” says SRAM road product manager Brad Menna.

It may be better to just buy a new bike.

If your bike is, ahem, of a certain age (say, pre-2010), then it may be better to look at a whole new bike, says Chad Nordwall, owner of Bay Area shop Above Category Cycling. It’s difficult to retrofit electronic shifting to some frames (see above) and if you’re already looking at spending close to $2,000 on a new groupset, “then from a cost-effectiveness standpoint, you should probably just get a new bike,” Nordwall says, and benefit from innovations like oversize steerer tubes and lighter, stiffer carbon fibre frames, plus disc brakes if you’re currently running rim brakes on your road bike. Di2-equipped bikes start around R60 000—no one’s idea of a bargain—but if you’re set on switching, it may be the smarter choice.

No, the battery won’t go dead.

Shimano makes no outright claims on battery life, says Legan, citing the broad range of terrain and conditions riders encounter. But, he adds, even pro riders don’t charge the batteries on their training bikes more than five to six times a season. Quarterly is probably enough for most riders. Far more common: A dead battery results because they last so long you forgot to charge it. (Tip: Set up a regular calendar reminder for, say, Friday evenings at the end of the month.) And don’t worry about outlasting the unit’s charge cycle life. Above Category has sold Shimano Di2 and Campagnolo EPS groups since they first came out, and Nordwall says he’s never seen a rider come back with a battery that’s totally dead. SRAM, the newest entrant, says its batteries last at least 15 hours—and up to 60—on a full charge.

LED indicators warn of low power, but even when it turns red to indicate a depleted battery, Menna says, you’ll have at least five hours of ride time before it goes dead. Plus, the front and rear derailleur batteries are interchangeable. If one does go dead mid-ride, “you can swap the live battery to the front derailleur, put it in the proper chainring and then put it back on the rear for shifting in back until you get home,” Menna says. You can also buy a spare battery and have one fully charged in your pocket if you’re out for a long day on the bike. When traveling, make sure your battery is removed while flying with your bike (the airline may ask about it), and recharge when you reach your destination, as some people report batteries draining during flights.

But you will need a charger.

Make sure what you’re buying—bike or group—comes with a charger. Shimano’s new internal battery system uses an E-Tube charger box that connects to any USB adaptor, but your bike will have to be stationed near an outlet to charge. Campagnolo uses an external charger setup. SRAM’s eTap also uses an external charger. With separate, smaller batteries for each derailleur, SRAM says a full charge takes just 45 minutes per unit—but there’s only room for one battery at a time, so make sure to leave enough time to power up both.

You can add an additional charging cradle to the system if you want to charge both batteries at once. You’ll also need to replace the CR2032 batteries in the shifters every one to two years, depending on how much you ride. Consider setting up a charging station in your garage with your bike lights, cycling computer, and your bike so you never run low.

Electronic shifting won’t go out of adjustment.

Di2 initial installation and setup are best handled by shops, says Legan, a former pro team mechanic for CSC and RadioShack. But once it’s done, an electronic drivetrain should shift exactly the same every time. “There’s no cable stretch, and the motor shifts the chain at the same speed, the same distance, every time,” he says. Indeed, that kind of bulletproof reliability is one of the biggest selling points for electronic shifting.

If your shifting’s not working, the culprit is likely a dead battery or a loose wire—check all connections. Shimano does make a (PC-only) software tool for customisation like reversing the shift button function or adjusting shift speed, but unless you’re a constant tinkerer, it’s probably easier just to take it to a shop. SRAM says a decent home mechanic can set up eTap. Since there’s no wiring harness except from the shifters to the stem-mounted CPU, Menna points out that once the derailleurs are bolted on and paired, setup is mostly a matter of adjusting limit screws and the B-tension screw on the rear derailleur. Then, adjust with the app: The SRAM AXS app lets your check your charge, change component behaviour and personalise controls, and update your firmware as needed.

Take care with tools.

Be mindful with any sharp tools, which could damage electrical wiring. And take care even with mundane tasks like re-wrapping the handlebar tape. “If the E-Tube wiring is under tension along the handlebar, when the tape compresses it, it can pull on the harness just enough to pop the E-Tube connector out,” says Legan. Leave just a bit of slack under the bars and double-check the harness connections to make sure they’re snug. Also: Never pull on the wires themselves. With SRAM, you won’t have to worry about spare wires, but if you’re using additional remote “Blips” shifters, take care when cutting handlebar tape so you don’t nick the wires from the Blips to the shift lever connection. You also will want to be more careful when washing your bike: Avoid pressure washing in general, but if you are spraying down a muddy bike at the car wash, be even more careful to skip the bottom bracket, handlebars and derailleurs.

Don’t ignore maintenance.

Precisely because electronic shifting is so good, Nordwall says, people are neglecting their bikes more. “Before, people had this kind of imposed maintenance alarm where their shifting would start to get bad and they’d bring their bike in,” he says. “Electronic is so good that by the time people bring in a bike it’s toast—the cassette is worn out, the chainrings are effed, and the jockey wheels are full of crud.” The problem is that stuff’s expensive—a Dura-Ace 9000 outer ring can be as expensive as R3 500. Regular cleaning, and swapping chains before they get too stretched and prematurely wear out the cassette and chainring teeth, can prolong the life of any drivetrain. Just because your shifting works fine doesn’t mean your bike doesn’t need a little TLC.

—Additional reporting by Molly Hurford

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