SRAM Unveils Eagle Powertrain | Here’s 7 reasons we’re excited about the long awaited e-MTB system from SRAM

After years of spy shots and speculation, SRAM has finally unveiled its e-MTB system — Eagle Powertrain.

Unsurprisingly, it’s designed to leverage everything that’s already under the Eagle AXS umbrella, like the T-Type Transmission, the wireless protocol and the app, into a slick, highly integrated system — for better or for worse.

There’s plenty to cover with this hotly anticipated new e-MTB system, so let’s power up and dive in.

1| So that’s what the extra button on the shift pods was for

When SRAM launched the T-Type Transmission, we were left scratching our heads as to why the left side shifter pod had two buttons. While one made sense to incorporate the AXS dropper, SRAM killed the front derailleur long ago, so this dummy button was a bit of a mystery, and Flight Attendant is still a little exclusive.

In a similar fashion to the UDH, there was a larger plan in motion, and now, all has been revealed. SRAM has utilised that extra button to replace the bar-mounted remote control for the e-MTB system.

Using the left-side buttons, riders can activate the dropper post and toggle between two different ride modes, Range and Rally  — more on this later.

The setup of the pod controllers can be totally customised through the AXS app, and they are smart enough to know the difference between a short and long push. So effectively, you can program eight functions into the four buttons covering shifting, dropper post and the e-MTB control without having to bolt anything else onto your handlebars.

Up to this point, the Eagle AXS parts have been more or less universally compatible — you can pair a T-Type rear mech to the AXS paddle shifters or even the drop bar shifters. However, SRAM says the Powertrain e-MTB functions will only work with the new pod shifters.

SRAM does say the Powertrain can be paired with mechanical or non-Transmission Eagle AXS drivetrains, but you’ll lose the Auto Shift and Coast Shift functionality. While there are probably some workarounds that are yet to come to light, we’d speculate that product managers aren’t going to spec bikes with limited functionality on purpose.

The same goes for the dropper. There aren’t any compatibility issues running something other than the Reverb AXS, but trying to fit the lever next to the pod controller would create an ergonomic nightmare. So you’re likely to be handcuffed to the Reverb AXS.

SRAM has designed a holistic system that leverages the unique features of the parts it makes, and with that, we don’t expect you’ll see many bikes with incomplete Powertrain systems. This does limit the system to a slightly higher price point, given the cost of entry into Transmission and a Reverb AXS are more costly than the cable-driven alternative.

2 | Auto Shifting and Coast Shifting

Following on from what Shimano introduced with its EP801 motor, SRAM’s Powertrain will also offer Auto Shift. This is precisely what it sounds like, and the system monitors your cadence and aims to keep it in an ideal range by managing shifts up and down the cassette without any rider input. Given how well the new Transmission shifts under power all of the time, we’re very interested in trying this one out in the real world.

All of the shifting decisions are based on your cadence, and SRAM tells us it does not utilise tilt sensors, like with Flight Attendant, to react to what the terrain is doing to make predictive shifts. These shift parameters can be customised in the AXS app, and according to SRAM, the system offers seven different steps to help riders find their ‘sweet spot.’ It also appears you can assign Pedal Speed to a long push on the pod shifters and change the target cadence on the fly — how cool!

Being that the drivetrain isn’t taking the terrain into account, Auto Shift can also be overridden by shifting as normal, say if there is a steep bump in the middle of a corner where you’ll need to drop a couple of gears. After a few seconds, it will revert back.

The new Powertrain also has the ability to Coast Shift, meaning you can move the chain up and down the cassette without pedalling. Again, similar to what Shimano’s EP801 system offers, the motor will advance the front chainring independently of the cranks, just far enough to advance the chain up or down the block.

There’s also Push mode, which is there to help you push/walk your bike up a steep hill by delivering up to 6kph of assistance.

3 | SRAM Powertrain by Brose

SRAM has outsourced the actual drive unit to German outfit Brose, who also produces the Specialized e-MTB motors. The brand tells us that the hardware is more or less the same as what you’ll find bolted into the current Specialized Levo. With that said, it has slightly different mounts, so you won’t be able to bolt a Powertrain into your Levo.

SRAM says it wanted to leverage an experienced hardware supplier rather than go at it totally alone. The brand was attracted to Brose in part because of how well the Specialized motors perform, but another big factor was how much has been done to address the issues with some of the early motors. While the hardware may be more or less the same as the Specialized 2.2 full-power motor, SRAM tells Flow all of the software was designed in-house.

And with that, SRAM has been able to eke out a bit of extra performance from the drive unit, offering 90Nm of peak torque and a quoted peak power of 680W — the Specialized unit tops out at 565W. That’s a lotta grunt!

Using a belt-driven motor, the power delivery is quiet and smooth, and it doesn’t sound like there is a percussion band chasing you down every descent like with the Shimano and Bosch units. The trade-off is that there’s a fair bit of resistance when you exceed the 25kph cutoff.

However, with SRAM utilising existing hardware and its own software, it brings up an interesting proposition in that software could potentially be adapted to a Bosch motor or an SL motor like TQ. This means the shift pods would run the show for a clean cockpit, and the same user interface could be applied but still have all the advantages these systems have to offer. As to how realistic that is, we can only speculate.

4 | Eliminating the Netflix effect by limiting power modes and adjustments

We’ve all opened a streaming service and have been completely overwhelmed by the sheer number of options, succumbed to decision fatigue, and ended up watching episodes of The Office you’ve already seen 400 times.

Some e-MTBs have half a dozen different assist modes and as many sliders in the app that can adjust when and how much power is applied, which can also induce decision fatigue — most people only use two or three anyway. To complicate things further, every brand has its own term for modes and the adjustment parameters — to the point we’ve even written LONG explainers to try to help folks decode what the heck all these buttons and sliders do.

Related:

• 10 Tuning Tips to get the most out of your Specialized Turbo e-MTB
• 9 tuning tips to get the most out of your Bosch electric mountain bike | Bosch Smart System Review

To remove this decision fatigue, SRAM is only offering two assist modes — Rally and Range — and within those, it only has two sliders to adjust.

While SRAM says Rally mode is for hooning and Range mode is for conserving battery, with the adjustments available in the app, you can make them do whatever you’d like.

Adjustments are limited to a pair of sliders. The first is max power, which puts a cap on how many watts the motor will deliver. The second slider is a range between dynamic and support, which tells the motor how to apply the power. The closest proxy we can come up with is the ‘Response’ slider in the Specialized Mission Control app.

With a dynamic bias, the motor will adapt to your inputs in the power it puts out, whereas the support side will give you full noise the moment you apply pressure to the pedals.

5 | One battery to rule them all — sort of

With all the components talking to one another, the big battery in the downtube can power the motor and your derailleur. While we have seen this a few times in the past, it hasn’t been a feature made prominent by the brands.

SRAM is offering a 630Wh and a 720Wh option and will also sell a 250Wh range extender. Claimed to weigh 3.9kg and 4.1KG respectively, SRAM says it came to these capacity numbers based on what its OEM partners were asking for.

This means you have fewer batteries to remember to charge, which, in our book, is a win. According to SRAM, if the motor runs the battery dry mid-ride and the AXS Bridge Toptube display shows 0%, the battery hangs onto a small reserve that should offer two hours of shifting and power for lights.

Interestingly, if you are using the range extender and you riding in Range mode, the system will drain the add-on battery first, whereas in Rally mode, it does the opposite.

With that said the wireless nature of AXS means the pod shifters still need coin cell batteries, and the Reverb AXS dropper post also does not wire into the main battery.

6 | There’s an app for that

SRAM’s AXS app is already well-polished for keeping your drivetrain shifting crisp and reminding you to keep your batteries charged. Instead of designing a totally new app for the e-bike system, Powertrain will integrate what you already have on your phone.

Inside, you can customise the ride modes, tailor auto shift parameters and assign functions to the buttons on the pod shifters with both short press and long press.

The app will also be able to conduct over-the-air firmware updates, diagnostics, and battery health, and display a drive unit odometer.

7 | What bikes will Eage Powertrain be available on?

At launch, SRAM says Eagle Powertrain will soon (ish) be available on bikes that are set to launch from Propain, Nukeproof, Transition and Gas Gas. That last one isn’t available in Australia — though we’re about 97% sure it’s coming, given the brand now has an Australian Instagram account — while the others have a pretty limited presence, especially for their e-MTBs.

So, until more brands jump on board with the SRAM Powertrain, it will be a little while before we start to see them in Australia, but watch this space!