In the land of e-bikes, there has long been a major player missing from the market. While nearly every other category is ruled by the two big S's of our industry, one has precariously sat by the wayside while others take on the electric assist world. But just like head angles continuously getting slacker, trail gear fitting tighter and tighter, or French racers winning World Cups on French soil, some things in life just aren't that surprising. Introducing SRAM's brand-new eMTB system: Eagle Powertrain. Never a question of if but when, Powertrain weaves together SRAM's AXS and Transmission technologies to deliver riders a simple and natural ride experience. Buckle up. The other S has landed.
Highlights
- 90Nm Brose motor tuned by SRAM
- 680W peak power
- Two assist modes: Range and Rally
- 630 & 720Wh battery (integrated or removable options)
- 250Wh Range Extender sold separately
- Top tube integrated Bridge Display
- No handlebar-mounted display or control switch options
- Integrated with Transmission and AXS Pod Controllers
- AXS derailleur powered by battery (optional)
- Auto Shift and Coast Shift features (only available with Transmission drivetrain)
- Battery life displayed in a percent
- Brands launching Powertrain-equipped models in the near future: Transition, Nukeproof, Propain, Gas Gas
Powertrain Philosophy and Overview
As you'd expect, Powertrain has been baking in the oven for quite some time. Able to observe competitors' products and features, SRAM set out to develop a system that would offer a new take on how riders perceive and experience an e-bike ride. From 30,000 feet above, Powertrain's main goals are to seamlessly integrate its e-components in the simplest way possible, allowing riders to focus more on the trail and less on optimizing the system. The ingredients required to achieve these goals began growing years ago with the introduction of AXS wireless components, and was followed by the UDH, which turned out to be a Trojan horse to enable the mass compatibility of Transmission drivetrains. Powertrain utilizes AXS connectivity to offer riders a wireless and easily adjustable system, while Transmissions' ability to shift under high loads compliments the demands of e-biking and opens the door for Auto and Coast Shift features. In the end, riders end up with a well-cooked product that might offer fewer features up front but aims to offer a holistic ride experience.
The hardware that makes up Powertrain includes a Brose motor, a 21700 cell battery, a rotor-mounted speed sensor, a top tube integrated Bridge Display, two AXS Pod controllers, an AXS Reverb dropper post, and a Transmission drivetrain. A wiring harness connects the motor, battery, and display, and the rear derailleur can be wired to the battery.
SRAM is launching Powertrain with four brands: Transition, Propain, Nukeproof, and Gas Gas. The launch of each bike will follow in the weeks to come.
SRAM-Tuned Brose Motor
Instead of developing their own motor, SRAM teamed up with Brose to create a motor package for Powertrain. Long-time experts in electronic drive units, most mountain bikers are familiar with Brose as they come specced on Specialized e-bikes. Powertrain uses a Brose-supplied motor programmed with SRAM-specific software to achieve unique motor characteristics. So while the hardware might be the same as other Brose-equipped bikes, its designed to work exclusively with Powertrain and the features of the system. Sorry, haters, it's not just a Levo motor with a SRAM logo slapped on the side.
SRAM-tuned software sounds nice and dandy, but what does that translate to on the trail? The defining characteristics of the motor (as described by SRAM) can be summed up as natural, intuitive assistance that responds to rider needs at any given moment. SRAM wasn't after record-breaking power output or having a motor that can pedal for you up the hill. Instead, they wanted an assist profile that anyone could ride and receive assistance to compliment their pedaling habits or riding style.
Keeping the theme of simplicity trickling down through the whole system, Powertrain only has two assist modes: Range and Rally. The self-explanatory names represent SRAM's realization that most e-bikers are either worried about battery conservation or having all the power all the time. Giving riders only two modes takes the guessing out of what mode to be in for any given instance. It also allowed SRAM to eliminate the need for a dedicated assist switch. Instead, the top button on the left Pod controller toggles between Range and Rally. Yes, other systems could operate with a single-button assist switch, but you'd end up with a thumb cramp having to cycle through modes. Both modes can be tuned within the AXS App, allowing riders to adjust max power (between 550W and 650W) and Assist percent.
Battery Options
Powertrain-equipped bikes will come with either a 630Wh (~3kg //6.6 lbs) or a 720Wh (~4.1kg // 9 lbs) battery. The 21700 cell batteries can be integrated or removable, and a water bottle-mounted 250Wh range extender will be available for aftermarket purchase. With the range extender installed, the system will drain the extender in Range mode and the main battery in Rally mode to maximize efficiency. A highlight of Powertrain that we know many riders will appreciate is battery life is displayed in a percent.
Transmission Integration
To think that SRAM has been co-developing Transmission alongside Powertrain for years is impressive and goes to show the foresight of their product developers. When Transmission launched in March, the key takeaways were the robust interface of the derailleur with UDH-compatible frames and its improved shifting durability under load (plus, you can stand on your freakin' derailleur).
Now that the cloak has been completely removed, it seems obvious that Transmission was always destined for e-bike application, even if SRAM was hesitant to say just that a few months ago. The components that make up Transmission are the exact same with Powertrain, the only differences being the additional functions of each Pod button, and the ability to wire the derailleur to the battery. And don't worry, if the Powertrain battery does completely drain, riders still have ~2 hours of shifting.
Auto-Shift and Coast Shift
Transmission's shifting performance under high torque is the secret sauce that allowed SRAM to develop Auto and Coast Shift. That, and the ability of the Brose motor to let the front chainring freewheel without pedaling. Auto Shift, in case the name left you confused, allows the bike to shift gears on its own based on speed and rider cadence. Riders can adjust Auto Shift by changing the cadence range that the motor seeks to keep you within. There are seven preset cadence ranges, and riders can switch between them via the right Pod Controller or in the AXS App. Bikes arrive set in 'Mid,' and the cadence range can be increased or decreased from there. Manual shifts can always be initiated and will supersede auto shifts. The feature can also be turned off entirely.
Coast Shift gives riders the ability to change gears when riding without pedaling. Auto Shift also takes advantage of Coast Shift to change gears based on speed. The easiest example of applying Coast Shift is ripping a descent that leads into an immediate, punchy climb; riders can prepare for the coming climb by dropping a few gears before they need to get on the pedals. The final puzzle piece completing these shifting technologies is SRAM's Speed Magnet and Ring. Instead of using a single magnet, the rotor-mounted Ring has six magnets to increase the accuracy and real-time reading of speed to better anticipate and engage auto-shifts.
All bikes initially launching with Powertrain will come with Transmission to enable Auto and Coast Shift. However, it is possible to pair Powertrain with non-Transmission drivetrains, the caveat being you'll lose the shifting features.
PODS + Integrated Bridge Display = Cockpit Cleanliness
The simplicity and integration of Powertrain can be seen best in the marriage of wireless Pod Controllers with the top tube integrated Bridge Display. Where most e-bike systems add wires to the handlebars, creating the need for additional cable management or the marginalizing headset routed option, a Powertrain cockpit looks the same as any AXS cockpit. The Pods are exactly the same as those sold with Transmission drivetrains, but each button now has two functions depending on if you press or hold it. Of course, the function of each button can be reconfigured in the AXS app to meet rider preference.
The Bridge Display is the only display available with Powertrain (e.g. No handlebar-mounted version exists). The full-color display only communicates select information, including assist mode, Auto Shift settings, if Auto Shift is on/off, and battery life. There are also two buttons on the display that perform multiple functions, the most notable being turning the system on/off and turning off the motor. For riders who crave additional information, the Bridge Display can be paired with ANT+ devices to access speed, remaining range, selected gear, and rider power.
"But wait, I can't run an AXS Reverb, it's too short!" For you long-legged rippers or anyone who wants to use another dropper with Powertrain, you can absolutely do so. However, there isn't a perfect solution for the Pod/dropper lever dilemma. Riders can replace the left Pod with a dropper lever but will lose the ability to change assist modes without reaching down to the display. You also lose Push Mode. The other option is to finagle a dropper lever around the left Pod. We haven't tried this to know if it can be done successfully. However, the thought of having two levers in the same space that weren't designed with each other in mind sounds like it defeats the whole goal of Powertrains' tidy cockpit setup.
On The Trail
Welcome to Bellingham!
Last week, I journeyed north to one of mountain biking's most trafficked riding destinations: Bellingham, Washington. A town filled with an impressive concentration of transplant mountain bikers that's only surpassed by the impressive concentration of trails in the surrounding hills, I've made the pilgrimage to B-ham a lot over the years. The home of Chris Mandell from SRAM and Lars Sternberg from Transition, I spent four days checking out Powertrain aboard a new Transition e-bike that'll launch in the near future.
A quick in-and-out strike mission, time was split between digesting a lot of e-tech and racking up saddle time. With the legality of e-bikes blurry in Bellingham, we rode mostly moto trails and connected zones I'd never ride without the help of a motor. One day, we even managed 30 miles and over 5,500 ft of climbing without touching the critically acclaimed Galbraith Mountain. Three rides and ~7 hours of moving time later, I left with a good idea of the performance and functionality Powertrain provides.
Interacting with Powertrain
Taking off on our first Powertrain ride, the lack of extra components or cables dangling from the handlebars and knowing the function of three out of four Pod buttons was a double win. I've found the learning curve with some e-bikes is steep, as figuring out what button does what and developing muscle memory to engage the correct button takes time. That was not the case with Powertrain and the Pod controllers. I only had to press the upper left button a few times to remember it swapped between Range and Rally, and then I was equipped with the necessary knowledge to operate the bike. Learning the 'long press' functions of each button took a tad longer to remember, but as I'll get into, I rarely engaged Auto Shift or messed with my Auto Shift settings.
The tactile feel of the Pod buttons was definite and solid, and I never accidentally double-pressed the button when changing modes— I can't say the same about nearly every other assist switch I've tested. After three days of riding, I never once wished there was a dedicated assist switch. The same goes for a handlebar-mounted display—with minimal information provided on the display and its low position in my field of view, I rarely glanced down at it. I'm not one to want a ton of information in my face during a ride, but for those who want their ride stats live and on-demand, connecting an ANT+ device is a simple solution. The only thing I wish the minimalistic display included was the time of day, as I don't ride with a watch and hate stopping to pull my phone out.
The Goldilocks of eMTB Motors?
Every e-bike motor on the market claims to provide power in a natural assist profile. Most do a good job amplifying rider input, but they usually require a specific riding style to maximize power, efficiency, and range. Shimano's EP8 motor likes a high cadence to deliver the most usable amount of power, while Bosch's Performance Line CX motor offers unfiltered power (especially in more powerful modes) that feels like someone is pushing you up the hill regardless of your input. In either case, I often cycle through assist modes, trying to match my speed and effort with the motor power to maximize efficiency.
What separated the SRAM-tuned Brose motor from other systems I've tested was its ability to operate in the background and provide the right amount of power regardless of my cadence, pedal input, or speed. Whether I was hammering up a steep climb or trying to get going again after stopping in a technical section, I was given the exact amount of power to amplify my efforts. I never experienced unpredictable power surges at slow speeds or through tight corners, and I received exceptional traction in steep sections.
The main benefit of the motor operating in this Goldilocks zone was the lack of thought I had to put into maximizing the system. If I wanted to cruise and chat on a fire road climb (also known as logging roads in the PNW), I could pedal leisurely. If I was breathing out my eyes, crawling up a nasty climb, I didn't have to question whether I was in the right gear, mode, or cadence. As much as I wanted SRAM's promise of a natural feeling, simpler e-bike experience to fall flat, I can't deny they developed a motor package that always gave me the power I wanted in a controllable manner.
The comparison I'm sure some are waiting to hear is how Powertrain compares to a Brose-equipped Specialized, such as the Turbo Levo. Having spent minimal time on a Levo over a year ago, I'm not going to compare the motor feel based on deteriorating memories. The Levo was an easy bike to hop and ride how I pleased, but a future head-to-head test is needed to understand the differences between the SRAM and Specialized software. Lastly, the motor's constant electric buzz wasn't bothersome or ear-piercing but was on the same decibel level as other full-power motors.
Auto and Coast Shift
After traveling to Europe earlier this year for a Shimano press camp dedicated to showcasing their versions of automatic and pedal-free shifting, it's hard not to wonder if SRAM debuting their first e-bike system with the same features wasn't a subtle dig at their main competitor. Speculation aside, my experience with SRAM's Auto and Coast Shift mirrored my time on Shimano's XT Di2 groupset. In a nutshell, Auto Shift left me yearning for more responsive shifts, while Coast Shift was a feature I used constantly throughout an entire ride.
AutoShift on Powertrain was significantly easier to comprehend and adjust than Shimano's version. Only having one parameter to worry about minimized tinkering and got me closer to an ideal setting faster. I increased the Auto Shift to +1, increasing the cadence window and allowing me to spin faster before the bike would shift up. I played around with Auto Shift on fire roads, undulating single track, and rough technical climbs, and found myself in every situation tossing in manual shifts to be in the right gear. It's great that technology is opening the door to such features, but it seems like there is room to improve how fast the system can read terrain. For now, Auto Shift seems best suited on trails with gradual speed and pitch changes to allow the system a brief moment to keep up and change gears.
Coast Shift functioned exactly like Shimano's Free Shift feature, allowing me to change gears to match upcoming terrain. I used Coast Shift most to drop a few gears going through awkward corners so I could exit in a pedalable gear, or to shift up a few gears on descents when I knew the gear I stopped pedaling in last was too low for my current speed. A feature I never thought would have such an impact on how I decipher a trail, I dream someday I'll be tossing in pedal-free shifts on my regular mountain bike.
It feels unjust to leave out any mention of how Transmission performed, even though we've praised its abilities a few times this year. This isn't the first e-bike I've ridden with Transmission, but I was again reminded of how the added power of a motor highlights its shifting capabilities. Transmission is legit, and its incorporation into Powertrain enabling Auto and Coast Shift is yet another feather in the cap of a truly durable and robust shifting platform.
Room For Improvement?
After three test rides, my general impressions of Powertrain were positive. Besides the complications of mounting a non-AXS Reverb dropper and the time of day missing from the display, I was impressed. I look forward to hearing how other riders perceive SRAM's simplistic approach and the calm feel of the motor.
What's The Bottom Line?
SRAM has created a complete e-bike package with unique features that separate it from competitors while offering legitimate advantages to riders. Powertrain may not raise the bar when it comes to motor power or battery technology, but the way riders interact with the system closely mirrors the experience of traditional mountain biking. There are fewer cables, fewer assist modes, and familiar controls that minimize the time spent understanding and operating the system. The motor's smooth and natural power delivery eliminates the need for unique pedaling techniques to optimize its performance, allowing riders to ride the same as they always have. The shifting abilities of Transmission give riders quality shifting performance with the addition of e-specific features if they choose to use them. Overall, Powertrain offers a wide range of riders a simple yet effective e-bike platform to get out and ride however they like.
For more information, please visit sram.com
About The Tester
Jason Schroeder - Age: 28 // Years Riding MTB: 16 // Height: 6' (1.8m) // Weight: 175-pounds (79.3kg)
A once-upon-a-time World Cup downhill racer turned desk jockey, Jason has spent years within the bicycle industry from both sides of the tape. A fan of all-day adventures in the saddle or flowing around a bowl at the skatepark, he doesn't discriminate from any form of two-wheeled riding. A SoCal native who doesn't spend too much time in any single place, you can find Jason camped out in his van most weekends somewhere on the West Coast.
9/28/2023 6:00am
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