The best electric drivetrain 2025: Sram XX Eagle Transmission vs. Shimano XTR Di2
Stefan Frey
· 21.12.2025
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When Shimano presented its first electronic mountain bike drivetrain in 2014 - still eleven-speed and wired at the time - it was like a revolution. Even back then, shifting via electrical technology fascinated with its effortless, direct response. However, the first Di2 did not find its way onto the mass market. Even experienced mechanics often despaired when untangling the tangle of cables or handling the separately positioned power supply, display and control unit. However, "Uncle Sam" dealt the fatal blow to the competition from Japan when the Americans launched an electronic MTB drivetrain in 2019: the XX1 Eagle AXS. It wirelessly shifted twelve instead of eleven gears on a cassette with an enormous range. Result: No more cables, no more front derailleurs, simplified assembly.
Sram leads the way with the transmission drivetrains
Even before Shimano was able to counter the AXS with a wireless version of the XTR, Sram surprised us with its next innovation in 2023. The new transmission technology made the derailleur hanger obsolete, fixed the rear derailleur directly to the frame and thus created a direct reference point to the cassette - making the adjustment screws on the rear derailleur a thing of the past. Setting up a mountain bike derailleur has never been so simple. Score one for Sram.
Shimano XTR Di2 - Much remains the same
We were therefore almost a little disappointed with Shimano's big comeback in the middle of the year: although the new XTR Di2 finally does without cables, it is fixed to the derailleur hanger in the classic way, which makes adjusting the rear derailleur a little more complicated than with Sram. On the other hand, the Japanese have completely dispensed with new standards. The initial assembly and coupling of the components is similarly simple. Fine-tuning the gear steps via the app is a real benefit compared to fine-tuning via the tension of mechanical groupsets. However, while the AXS app automatically recognises available components, the Di2 has to be manually set to connection mode - and disconnected again. Annoying if you've already put your smartphone back in your trouser pocket.
A matter of taste - the controllers
The first big difference is immediately apparent when you set off. While the AXS is ready to shift immediately, the Di2 needs a few metres to wake up from sleep mode. With the compact Pod Controller, Sram is consistently committed to digital, as shifting via the two crisply defined buttons is almost like gaming. The somewhat clunky Shimano shifter, on the other hand, has real mechanics and is more reminiscent of the feel of a classic gear lever. Both paddles can be adjusted extensively, but are quite close together and feel less defined. There is agreement on the function: if you hold down one of the levers, both derailleurs will shift the chain once across all twelve sprockets if required. The Shimano shifter offers a little more functionality overall: if you press the button, the Di2 shifts two gears at a time - the function can also be deactivated if required. The Di2 lever also has a third button that can be individually assigned. For example, for controlling a bike computer.
XTR Di2 - shifting like at speed
Even in the middle of five selectable speed modes, the Di2 is extremely fast. At the highest level, the chain flies over the sprockets like a weasel at speed. At a low cadence, however, this is too much of a good thing and the gears easily get bogged down. The fact that the AXS can't quite keep up in terms of speed is due to the design of its cassette. Shifting only takes place at clearly defined shifting lanes - Sram calls this technology X-Sync. However, in conjunction with the extremely stable connection of the rear derailleur to the frame, this results in ultimately smooth gear changes.
XX Eagle Transmission - Precision above all else
In general, the XX Eagle Transmission lifts the chain onto the sprockets with almost surgical precision. Up and down, when rolling as well as under full load. The Sram also reliably engages several gears at a time - one after the other - and does so almost silently. The slight delay from gear to gear is more a matter of getting used to than a disadvantage, because in practice there is hardly a situation in which the XX would be too slow - especially after the latest update, which now speeds up shifting slightly when using more than three gears. In terms of precision, the Shimano with its Hyperglide+ cassette, which we already know from the mechanical XTR, comes out on top. Don't get the wrong idea: The Di2 also changes gears extremely reliably. However, under load and when shifting through the gears quickly, the rear end can get a bit banging.
Special components for e-bikers - Shimano Linkglide
If you want smoother gear changes under the high load of the motor torque, especially on an e-bike, you should take a look at Shimano's Linkglide components. These have been specially designed for use on E-MTBs, have a more robust construction and are equipped with similar shifting lanes as the transmission drivetrains. We have already been able to test Linkglide on the new XT Di2. The gear changes here are indeed somewhat smoother and quieter. However, the shifting speed is noticeably slower than with the "normal" Di2 drivetrain, even at the highest level. You also have to do without the twelfth gear with Linkglide. The system runs on a cassette with only eleven gears.
Fallback functions protect the technology
Incidentally, both rear derailleurs also have a slip function to protect the expensive technology. Shimano and Sram rely on a slipping clutch that enables the rear derailleur to move inwards in the event of rock contact, for example. The rear derailleur then returns to its original position. While Shimano relies on rounded shapes for better sliding over obstacles, Sram enables its rear derailleur to move backwards via the full-mount connection.
In practice, we have had good experiences with both systems so far. The option of resetting the Sram rear derailleur after a crash by hand or by opening the thru axle is particularly practical. In our opinion, this is a better solution than continuing to rely on the derailleur hanger as a predetermined breaking point.
Electrical circuits - the subtle differences
The picture is similar to that of shifting gears on bumpy descents, where the firm rear shock reliably keeps the Sram rear derailleur under tension and thus ensures calm, while the Shimano rear derailleur with double tension spring bounces more easily and sometimes rattles. It's the little things that make all the difference: The derailleur cage cannot be decoupled for wheel removal as with Sram.
Although the battery is well protected in the rear derailleur cage, removing it is fiddly. In addition, the battery status is not automatically displayed on the rear derailleur. These are nuances - and yet they are the decisive factor in the lack of the next big XTR revolution 16 years after the invention of the first electronic shifting system.
In my opinion, both manufacturers offer absolutely top gears. Personally, I like the feel of the new XTR shifter. Outside of racing, however, I can do without the speed of the Shimano and would rather opt for the smoothness of the Sram drivetrain. - Jan Timmermann, BIKE test editor
Shimano XTR M9200 Di2 - Info, weights, prices
Prices / Weights
- Rear derailleur (long cage) 665 Euro / 390 g
- Controller (clamp mounting) 235 Euro / 105 g
- Cassette (10-51 teeth) 505 Euro / 367 g
- Chain (126 links) 79 Euro / 268 g
- Crank handle (170 mm / 32 teeth) 500 / 593 g
- Battery 64 Euro / 23 g
- The Shimano XTR M9200 Di2 groupset is, for example available here
Translation / Options
- Bandwidth / gradation 510 % / 10-12-14-16-18-21-24-28-33-39-45-51
- Chainrings 28 / 30 / 32 / 34 / 36 / 38
- Crank lengths 160 / 165 / 170 / 175 mm
- Cassettes 10-51 / 9-45 teeth
- Special featuresAdjustable shift paddles; shift speed adjustable in five stages; auto-shift with Shimano / Bosch motors; sprockets 10 to 18 individually interchangeable
Rating Shimano XTR Di2
Advantages and disadvantages of the Shimano XTR Di2
+ High shifting speed
+ Shifter extensively adjustable
+ can be retrofitted to all frames
- more complex setup
- less defined shifting feel
- less precise under load
- higher noise level
With the XTR Di2, Shimano missed the opportunity to deliver a truly innovative wireless drivetrain. In terms of setup and shifting precision, the Transmission is clearly ahead. No derailleur currently shifts gears more smoothly. I only know of one situation in which the XX Eagle reached its limits in terms of speed, but this problem has been resolved with the latest update. Stefan Frey, BIKE test editor
Sram XX Eagle Transmission - Info, weights, prices
Prices / Weights
- Rear derailleur 700 Euro / 441 g
- Controller (clamp mounting) 240 Euro / 46 g
- Cassette (10-52 teeth) 660 Euro / 377 g
- Chain (126 links) 150 Euro / 274 g
- Crank handle (170 mm / 32 teeth) 600 / 549 g
- Battery 63 Euro / 25 g
- The Sram XX Eagle Transmission groupset is, for example available here
Translation / Options
- Bandwidth / gradation 520 % / 10-12-14-16-18-21-24-28-32-38-44-52
- Chainrings 30 / 32 / 34 / 36
- Crank lengths 165 / 170 / 175 mm
- Cassettes 10-52 teeth
- Special featuresRemovable bashguard; no derailleur hanger and adjustment screws; setup sprocket; cage lock for setup/wheel removal
Rating Sram XX Eagle Transmission
Advantages and disadvantages of the Sram XX Eagle Transmission
+ clear and simple setup
+ highest shifting precision
+ strong friction damper
+ very quiet
+ rear derailleur override function
+ spare parts for rear derailleur
- very expensive
- only fits frames with UDH derailleur hanger
Weights, prices and the overall rating in comparison
Stefan Frey
Editor
