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Sram Eagle Powertrain in laboratory and practical testsPower house with smart auto-shifting

Florentin Vesenbeckh

 · 07.05.2024

Srams Eagle Powertrain is not yet to be found in many bikes. Our test bike is a Gasgas ECC.
Photo: Georg Grieshaber
Sram's Eagle Powertrain wants to revolutionise the e-bike market with automatic shifting. But the motor is an old acquaintance. We have extensively tested the Brose Drive SMag in Sram guise in the lab and in practice.
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The unique selling point of the Sram Eagle Powertrain is not the motor itself, but the combination with Sram's Ecosystem and in particular the wireless AXS wireless shifting system. This enables the Americans to provide automatic shifting functions and gear changes while rolling. Details can be found in our detailed presentation of the Sram e-bike system. However, this test is explicitly about the "motor" component. And here Sram relies on hardware from Brose. Specifically, the Drive SMag, which is also the Specialized Turbo Levo drives, is used.

Looks like a Brose motor, is actually a Brose motor. The Drive SMag in the Eagle Powertrain is equipped with a software controller from Sram. However, the hardware is identical to other versions of the Berlin unit.Photo: Georg GrieshaberLooks like a Brose motor, is actually a Brose motor. The Drive SMag in the Eagle Powertrain is equipped with a software controller from Sram. However, the hardware is identical to other versions of the Berlin unit.

On the software side, Sram emphasises that the powertrain has a completely unique configuration. Specialized also attaches great importance to the fact that the turbo motor in the Levo cannot be compared with other Brose bikes. In our experience, however, the basic character and power delivery of the various Drive SMag versions are very similar.

The facts about the Sram Eagle Powertrain

  • Weight: 3.1 kilos
  • Battery sizes: 720 Wh (4.1 kg) or 630 Wh (3.1 kg)
  • Optional: Range extender with 250 Wh
  • Drive modes: Range, Rally
  • Performance data (max.) from the laboratory: 87 Newton metres, 544 watts
  • Automatic gearstick in combination with Sram Eagle AXS Transmission
  • System updates possible via the app
We measured all drives on a roller dynamometer in the PT Labs test laboratory. The power is measured at the rear wheel.Photo: Adrian KaetherWe measured all drives on a roller dynamometer in the PT Labs test laboratory. The power is measured at the rear wheel.

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The character of the Sram e-bike motor

Although the Brose Drive SMag is particularly powerful with its enormous torque, the e-bike motor does not feel impetuous at all. The thrust is rather uniform and discreet. Together with the comparatively pleasant background noise, this results in a well-rounded, unagitated riding experience. The motor sound is not drastically quieter than a Bosch or Shimano, for example, but the low frequency makes the noise subjectively more pleasant. Nothing rattles downhill, which is also due to the solid bolting of the battery. Sram's Eagle Powertrain is the quietest candidate among the power motors in our test. However, the latest version is no longer as whisper-quiet as the Brose motors used to be.

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The powerful Brose motor shows its strengths on steep and steeper climbs. It pushes stoically over obstacles with massive torque.Photo: Thomas WeschtaThe powerful Brose motor shows its strengths on steep and steeper climbs. It pushes stoically over obstacles with massive torque.

The power delivery of the Sram Eagle Powertrain

The strong thrust from the bottom and the highest torque in the test set the tone for the powertrain. At low cadences, the powerhouse pushes really hard. Off-road, this is particularly helpful on steps when you run out of momentum while riding. The motor then heaves the bike powerfully over obstacles. No other motor in the test offers such strong support when the cadence drops towards zero and the situation already seems lost. The propulsion is more uniform than overly lively and reactive. Together with the comparatively pleasant background noise, this results in a well-rounded, unagitated riding experience. Good: Even at a very high cadence, the Drive SMag pulls away well.

Sram's Eagle Powertrain has the highest torque (in Nm, right ordinate) of all test specimens. The power curve (in watts, left ordinate) is correspondingly high at low cadence (X-axis, rpm). Pulls well at high cadences, on a par with Bosch and Co.Photo: PT LabsSram's Eagle Powertrain has the highest torque (in Nm, right ordinate) of all test specimens. The power curve (in watts, left ordinate) is correspondingly high at low cadence (X-axis, rpm). Pulls well at high cadences, on a par with Bosch and Co.With 87 Newton metres, the Eagle Powertrain is the motor with the highest torque in the EMTB lab test. The maximum power output is on a par with Shimano and Bosch. Even with low rider input, it pushes powerfully.Photo: EMTB MagazinWith 87 Newton metres, the Eagle Powertrain is the motor with the highest torque in the EMTB lab test. The maximum power output is on a par with Shimano and Bosch. Even with low rider input, it pushes powerfully.In the lower cadence range (X-axis, rpm), the Sram Powertrain is above all other test specimens. This shows its very high torque. The peak power is roughly on a par with Shimano and Bosch, but the power is slightly lower between 60 and 90 rpm. Pulls well when cranking fast.Photo: PT LabsIn the lower cadence range (X-axis, rpm), the Sram Powertrain is above all other test specimens. This shows its very high torque. The peak power is roughly on a par with Shimano and Bosch, but the power is slightly lower between 60 and 90 rpm. Pulls well when cranking fast.

Display & Remote

Keep it simple is the motto at Sram. Instead of a wide range of options and crazy features, the Eagle Powertrain only has a stylish but minimalist display. The AXS Bridge Display sits in the top tube and also serves as the interface between all AXS system elements. Only the riding mode, battery status and autoshift mode are displayed, there is no more information. The stylish screen in the top tube doesn't even reveal the speed.

Keep it simple: The AXS Bridge display only shows the riding mode, battery status and autoshift mode.Photo: Georg GrieshaberKeep it simple: The AXS Bridge display only shows the riding mode, battery status and autoshift mode.

Operating the system is very intuitive, partly because Sram only provides two support levels and a very reduced display. The control levers for the new Sram drive are the push buttons (called pods), which we already know from Sram's AXS wireless drivetrain. They work wirelessly, something that hardly any other remote unit for an e-bike motor on the market can do. Special feature: The operation is fully harmonised with other Sram components such as the AXS dropper post and AXS drivetrain. The entire system can be configured and fine-tuned via the AXS app.

The AXS pods work wirelessly. At the top, you switch back and forth between the two U-steps, while the AXS telescopic support is operated at the bottom.Photo: Georg GrieshaberThe AXS pods work wirelessly. At the top, you switch back and forth between the two U-steps, while the AXS telescopic support is operated at the bottom.

The batteries for Srams Eagle Powertrain

Two compact Intube batteries with 720 (4.1 kg) or 630 watt hours (3.1 kg) are available for the Sram system. The small version has a strong weight-to-capacity ratio, while the 720 is worse. A range extender with 250 Wh also fits on the down tube - but this is not yet available on the market.

The 630 battery for Srams Eagle Powertrain is light at 3.1 kilos. It can be tightened in the down tube without rattling using the solid screw.Photo: Georg GrieshaberThe 630 battery for Srams Eagle Powertrain is light at 3.1 kilos. It can be tightened in the down tube without rattling using the solid screw.

App and connectivity

The familiar AXS app from Sram also works for the new e-bike drive. All AXS components on the bike are controlled via the bridge display - which in turn establishes the connection to the app. All system components can be updated here. Updates are therefore possible directly "over the air".

The support levels can also be fine-tuned via the app. This is particularly important with the Eagle Powertrain, as it is not exactly well equipped with two modes. The function will therefore probably be used more frequently here than on most other drives. In the factory set-up, the range mode is already much more powerful than the familiar eco levels of the competition. Each mode can be tuned in two parameters: Maximum power and percentage of assistance, i.e. how hard the rider has to pedal for full thrust. Great: The settings for the automatic gearstick can be made very intuitively using the buttons on the handlebars. There's no need to use the app.

The entire system with all AXS components can be configured and fine-tuned via the AXS app.Photo: Georg GrieshaberThe entire system with all AXS components can be configured and fine-tuned via the AXS app.

EMTB review of the Sram Eagle Powertrain

The motor sound is not drastically quieter than a Bosch or Shimano, for example, but the low frequency makes the noise subjectively much more pleasant. Nothing rattles downhill. The thrust is uniform and very powerful, especially at low cadence.Photo: EMTB MagazinThe motor sound is not drastically quieter than a Bosch or Shimano, for example, but the low frequency makes the noise subjectively much more pleasant. Nothing rattles downhill. The thrust is uniform and very powerful, especially at low cadence.

Strengths

  • High torque
  • Intuitive operation
  • Quiet, even downhill
  • Roller shifting and automatic shifting

Weaknesses

  • Little information on the display
  • Only two U-steps
  • Heavy

Conclusion on the Sram Eagle Powertrain

Innovative complete system with smart shifting features and intuitive operation. The motor scores with its high torque and pleasant background noise. Lightweight 630 battery! - Florentin Vesenbeckh, Deputy Editor-in-Chief EMTB Magazine
Florentin Vesenbeckh is deputy editor-in-chief at EMTB Magazine.Photo: Max FuchsFlorentin Vesenbeckh is deputy editor-in-chief at EMTB Magazine.

Bikes with Sram Eagle Powertrain

The selection of bikes with Sram drivetrains is currently still limited. Propain, Gasgas, Transition and Nukeproof rely on the motor concept from Schweinfurt. You can find all the information and details about the e-MTBs in the links:

Florentin Vesenbeckh

Florentin Vesenbeckh has been on a mountain bike since he was ten years old. Even on his very first tour, he focussed on single trails - and even after more than 30 years in the saddle of an MTB, these are still the quintessence of biking for him. He spent his youth competing in various bike disciplines and later his cycling career was characterised by years as a riding technique coach. Professionally, the experienced test editor now focusses on e-mountainbikes. In recent years, the qualified sports scientist and trained journalist has tested over 300 bikes and more than 40 different motor systems in the laboratory and in practice.

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