SRAM Eagle Powertrain: Features, Specifications, and Reviews for Australian E-MTB Riders

The Eagle Powertrain is SRAM's foray into the world of e-bike motors and arrived late last year, but due to product and factory availability this is one of the first available in Australia. We were able to spend some time on the Eagle Powertrain in the new Gas Gas MXC 5, which was a pleasure. While the unit still seems quite large compared to other new offerings on the e-bike market, it has some very unique features that make the Eagle Powertrain stand out in the ever-busy e-bike market.

The Eagle Powertrain makes sense with SRAM: it is fully integrated with its Transmission drivetrain that combines its power delivery with its ability to shift under load. Based on Brose's Drive S Mag motor (which some of you may know from Special E-bikes) the unit is heavily developed by SRAM in terms of software. The Powertrain boasts the same technology as the Brose Drive S Mag with belt drive power and a double clutch system, with updates to remove some of the critical issues encountered in previous Brose units. These updates ensure that there is no noticeable resistance when moving without motor assistance, and you can still pedal easily in the event of an empty battery or when you switch to high-speed assistance.

Like the Brose S Mag, the Powertrain drive unit produces 90 Nm of torque and weighs 2.98 kg. With its maximum power of 680 watts, this makes the Powertrain even more powerful than the ever popular Bosch Performance Line CX with its 600 watt size.

Batteries and Range Extenders

There are two different battery options to power the engine; the smaller 630 Wh weighs 3.1kg, and access goes under the bottom tube. There is a screw under the battery cover that must be loosened before you can remove the battery with the metal guard clips that hold the battery in place, so that it doesn't just pop out of the frame once you've loosened the screw (it will take a little pulling to loosen it and take it out, more of an intentional act than an accident).

The larger 720 Wh version can slide out the bottom tube end or be permanently integrated. At 4.1kg, it weighs a kilogram less than the smaller compact size version. It is up to the types of bikes and their concepts to decide which battery they choose to be permanently integrated or removable.

For the long-distance riders among you, SRAM also offers a 250 Wh range extender that looks and fits like a water bottle, using a special extended mount. SRAM has designed a bottle cage that attaches to the distance extender bracket, so you don't have to remove the bracket every time you want to carry a water bottle instead of the distance extender.

What you should be aware of before buying a range extender is that the engine can only go into the range extender if you put it in Range Support mode, as Rally mode draws its power from the main battery to preserve battery integrity. More on Range and Rally modes below.

Technologies, Modes and Applications

SRAM has developed its own software that should help reduce load peaks and further reduce strain on the belt system. With a huge investment, knowledge and brains trust all things with bikes, SRAM software (which helps with the above driving problems) improves their knowledge of batteries, electronic controls, and application integration; everything designed for the Powertrain from the ground up.

The two driving modes are Range and Rally. SRAM's idea is that riders focus on two things: increasing the range of long travel, or having a powerful, high-speed ride. These two options occurred during the test and appear from the feedback given by their 'Black Box' riders, where they usually used the eco style mode or the full power mode and didn't really use the middle ground. Personally, I tend to agree…but I may be from a small group that goes both ways. Maybe this is because I spent a long time on the Powertrain system.

While there are only two modes compared to the seemingly endless options of other motors, SRAM allows you to tune these modes around power and assistance to the rider. Just find the unit in the SRAM app, go to Eagle Powertrain, and tune into Ride Mode. From here, you can set up advanced car support, assistance and adjust the level of assistance in each mode. You can also check the battery life of all SRAM components and set your desired control preferences.

On the router, you can move between modes using the pod shifter or the integrated top tube display. What you choose here can also depend on your Reverb AXS going down and how much you end up relying on SRAM's automatic shifting feature…

Automatic switching and coasting

Both SRAM and Shimano released their automatic transmissions in 2023 to improve e-bike drivetrain performance. SRAM says the auto-shift allows the rider to fully concentrate on the track without worrying about changing gears. You can remove your shifter completely: an unusual idea.

As a digitally controlled system, SRAM will continue to provide software updates and evolutions of SRAM Transmission, meaning that auto-shift is always evolving and improving and users will not be left behind.

SRAM says the average rider makes about 200 gear shifts per hour, but the SRAM auto-shift currently makes about 700 gear shifts per hour depending on the terrain, to ensure smoothness and efficiency. However, it cannot move stationary as the motor can only turn the chainring when the rear wheel also turns, allowing the cassette to turn. In the default setting, the algorithm takes 85 RPM as the ideal cadence and selects the gear accordingly.

Something you may notice on Powertrain bikes is that the derailleur is not always powered by a separate AXS battery, rather it is connected directly to the main battery. This means you can only change gears when the system is on, which can be annoying when you're working on your bike, if you don't want help or the battery is completely flat.

You can use the pods to move your desired cadence up or down in three steps while riding. However, you can always shift manually, even if you have activated auto-shift (unless you ride without shifter pods or limit them to another task). Doing so bypasses the algorithm and disables it for about 5 seconds. I think if you find yourself making this automatic switch it might not be for you. Not for me, yet.

The coast-shift function is one of the best features and is very Honda-esque of the early 2000s downhill racer. What allows you to shift without having to step is always available, even if the automatic shift function is disabled and it is bright. Not much to add to this other than it does what it says, works great and I want it for my analogue bike. Knowing you can be in the right gear going into a climb or as the trail opens up and not need to pedal is a novelty that never gets old.

Additional Combinations: Hammerhead

Those of you out there looking for more information or data and lucky enough to own a new generation Hammerhead Karoo head unit can use the ANT+ LEV E-Bike support on Hammerhead to get a range of useful and cool data fields related to your Powertrain. A useful tile for those who want to ride in Rally mode is mostly rider vs motor power; it is a good judge of how you burn your physical energy and build up fatigue in your legs.

Being able to keep less fatigue in your legs when pushing around the e-bike should lead to less fatigue and help you ride more trails faster and have more fun. If your legs are gone the descent won't be as fun or faster, and it's more difficult if you have tough technical parts when you're maneuvering a 20kg bike. If you're that way inclined, you can also use this to see how well the Clips vs Flats debate works and whether it's fast or fun that you're looking for.

Final thoughts

To me, a system like SRAM's Powertrain makes a lot of sense especially as a current SRAM Transmission user. The way it all works with the rest of the AXS ecosystem is bright, incredibly customizable (yet usable) and hard to fault. The downside to all the upside is that you need a Transmission to get the full benefits of the Powertrain, but it set the benchmark for me on how I would want a racing drive system setup: and the shifter is just the best thing ever. and you can't change my mind.