SRAM has today launched a completely new e-MTB ecosystem called Eagle Powertrain, which is designed around existing key SRAM technologies such as Eagle Transmission, AXS wireless tech, and its associated software to build a complete system that could be one of the best e-MTB motors on the market.
The Chicago-based brand has always done things differently, whether removing multiple front chainrings and gear cables, or creating fully automatic suspension systems, and Eagle Powertrain looks to continue this revolutionary form. While specifics of the new motor have only just been made available, it's been hiding in plain sight for a while now – not least with a prototype on a GasGas bike at Eurobike.
The system is a full-fat MTB race setup with a powerful motor and large battery options. It's already seen success at the highest level with Yannick Pontal, who won the 2022 EWS-E series onboard the then unnamed system on his GasGas race bike.
SRAM tech working in harmony
Different manufacturers make many components on modern bikes, for example, a motor from Bosch, a drivetrain from Shimano, brakes from Hope, etc. SRAM is pretty unique as it is made up of many different component brands that are designed to all work together. This enables the company to design pretty much everything, bar the frame and tires and Powertrain now ties everything together giving a high level of integration and simplification for the rider.
The AXS wireless system has been a solid performer for years. Eagle Powertrain harnesses the AXS hardware and software already available for its controls. Powertrain uses a Pod wireless shifter as the main means of operation, which helps to give a clutter-free handlebar setup with controls that can be configured to best fit the rider's needs.
Used with an Eagle Transmission drivetrain, standard setup means motor and AXS dropper controls come via the left-hand Pod shifter and gear shifts from the right – using a combination of short and long button presses on each two-button Pod controller.
There's no handlebar-mounted display, but a top tube-mounted screen is referred to as the AXS bridge display to show basic info, much like Fazua and Specialized’s current setups. In keeping with the less complex nature of the new system, there are only two support modes, Range and Rally, instead of the usual four or more modes from eco to boost or turbo. Range mode is designed for longer routes or anywhere you need the extra distance, while Rally gives you access to full power.
SRAM has also taken the current AXS shifting and turned it up a notch with Auto Shift. It’s a system where the rear mech shifts automatically into the perfect gear based on a pre-determined cadence range and can even change gear when you are freewheeling thanks to the Coast Shift feature. Here the motor spins the chainring and chain separately to the crank arm and changes gear without you having to move your feet. Now this isn't the first time we've seen an e-MTB with Auto Shift function, as the current Shimano EP801 when paired with Di2 Linkglide, has an auto coast and shift setup, but the combination of the ability of the T-Type Transmission drivetrain to shift under load and the various accelerometers and sensors used on the Eagle system promise to make this the most natural feeling automatic shifting system out there.
What’s most interesting though is the seeming simplicity of the system. Currently Auto Shifts are only triggered by cadence (how fast you’re pedaling) while Coast Shifts are triggered by changes in wheel speed. This is monitored by six magnets on the rear hub disc brake mount and engages the motor to spin the chainring and chainring to shift the gears even if your feet are still.
A new motor from a familiar partner
The motor has been developed with Brose, which might surprise a few as SRAM purchased the motor company Amprio earlier this year. They have worked together to develop a motor to use Brose’s proven belt technology but address the shortcomings of other motors used for hard riding and the demands the EDR race series can put on them. SRAM has always used its athletes on the Blackbox program to develop and push its technologies, and this is no exception.
The e-MTB motor has humble beginnings, Brose being one of the early adopters adapting power steering motors to add power to trekking bikes, but the needs of a high-level e-enduro rider are a far cry from those early days. The Brose motor system uses a system of internal belts, instead of the more common geared systems, which results in a quieter operation. SRAM says it has also spent a lot of time addressing heat build-up issues that can plague other high-end race-orientated systems by using materials that are more resistant to overheating and a heat shield. In fact, it claims it has the best-in-class derating figure – which is the rating given to the difference between heat versus power loss.
SRAM Eagle Powershift first ride impressions
Our technical editor, Guy, has already been testing riding a SRAM Powershift equipped Nukeproof bike and has been seriously impressed...
"Despite deliberately picking the worst possible trails for sudden, almost completely flow free changes in speed, steepness and power requirements Powertrain blew me away. Within a few minutes I’d worked out what mode worked best for me and from then on I just surrendered gear control to SRAM.
"I’m not going to claim the system is perfect but even with over 40 years experience pre-judging gear selection, it was at least as good as I am. It’s definitely better than me in Coast Shift mode – where it spools up the chainset to shift into the appropriate gear for your speed without your feet moving. As someone with hard wired reflexes I was amazed just how quickly interaction became intuitive. You can still use the Pod controllers as over-ride shifters, but within a couple of runs up and down the hill I was just slightly adjusting my pedal speed to control the Auto Shift instead.
"From there on, it was just a case of marveling at just how good the rear mech performed while I kept charging full power. Auto Shift did its thing so seamlessly that apart from the cadence change, only an occasional gear growl told me something was happening. One unexpected side effect was that chasing the next upshift rapidly became the best game ever. Perhaps it’s more of a reflection on me and is something that will fade with familiarity charging up twisting tech singletrack at downhill speeds while laughing like a maniac because the only control you’re touching is the the rear brake is an absolute blast."
Find out more on why Guy gave the system a full five stars, in his SRAM Eagle Powertrain first ride review.
Numbers-wise, it has nailed the current sweet spot for EWR racers and e-MTB trail riders alike, with up to 90Nm of torque (5Nm more that Bosch CX or Shimano EP801) and 680W of peak power for those occasional super-techy climbing sections, married with a quiet natural ride feel.
Two batteries will be available at launch, a more compact 630Wh option or a full-size with a 720Wh capacity. There will be two versions available to manufacturers – a uniquely C-shaped clip-in version or a more standard slide-in style. There will also be an aftermarket range extender available with an additional 250Wh for those backcountry epics.
Four MTB brands have already been working with SRAM to run Eagle Powertrain on their forthcoming e-bikes, with models from Propain, Nukeproof, Transition and GasGas on their way.
For more information, check out SRAM.com.
Tech specs: SRAM Eagle Powertrain
- Motor torque: 90Nm
- Peak power: 680W
- Power modes: Range and Rally
- Drive unit weight: 2.9kg
- 630Wh battery weight: 3.1kg
- 720 battery weight: 4.1kg