After two years of testing on the EWS-E and EDR-E circuits, SRAM's new e-bike motor is making its public debut. It's called the Powertrain, and it produces 90 Nm of torque with 680 W of peak power. There will be two battery size options – 630 Wh and 720 Wh, along with a 250 Wh range extending external battery.
Now, the launch of a motor is a little different than a drivetrain, brakes, or suspension, since it's not a part that can be attached to an existing bike. That means there's no price tag, and information about the bikes that will used the motor is still on the way - Nukeproof, Propain, GasGas, and Transition all have new models designed around the Powertrain.
• 90 Nm torque, 680 W peak power
• Uses AXS pod controller to switch between Rally or Range modes
• AutoShift + CoastShift options
• Drive unit weight: 2.9kg
• 630Wh & 720 Wh battery options
In a slightly unexpected twist, the motor hardware is manufactured by Brose, and then SRAM handles the software. Specialized takes a similar tactic with their motors, which are also manufactured by Brose. WIth the Powertrain motor, SRAM's dealer network will handle any warranty issues, which means there's a very broad selection of shops that riders could go through if they encountered any issues.The Basics
The Powertrain is designed to integrate with SRAM's existing AXS and Eagle Transmission components, one of the reasons the marketing materials around the system keep mentioning the word 'holistic.' Rather than being a standalone, independent component, the motor is designed to function with SRAM's existing drivetrain and dropper technologies. The approach makes sense from a business standpoint, since it allows SRAM to bundle various components into one package for a prospective bike company.
SRAM focused on making the Powertrain simple to use, one of the reasons there are only two motor modes, Rally and Range. As the names suggest, Rally puts out the most power, and Range is for maximizing battery life and traveling a little less quickly. The max power and assistance level for each mode can be customized in the AXS app, allowing riders to adjust the motor's behavior depending on their riding preferences.
Switching between the two motor modes is done via the upper button on the left pod shifter, and the lower button is used to activate the Reverb AXS dropper post. I was surprised to learn there wasn't any way to turn the assistance completely off from the remote. That's something I regularly do when descending extra-technical sections of trail – I'd rather not have any more assistance than necessary in those low grip, heavy braking moments, and on most other eMTBs it's possible to switch the motor to the 'off' mode from a handlebar remote. With the Powertrain, it takes a press of the button on the top tube to switch the motor off, which isn't always that easy to do on the fly.
There's also a walk mode (SRAM calls it a Push mode) that's activated by holding down the top pod button and walking the bike forward; it'll provide support to get the bike up and over un-rideable sections until speeds exceed 6 km/h.
The fact that there's no dedicated, standalone remote does seem like an oversight to me. I understand SRAM's desire for full integration, but the fact that there's currently no 200mm Reverb AXS dropper post means riders who want a longer travel dropper will be forced into an awkward cockpit configuration, where two under-the-bar remotes will be fighting for space
. I'm curious if any companies running the Powertrain motor will spec a dropper post other than the Reverb AXS; if not, there will be a lot of taller riders out there wishing they had a post with more than 170mm of drop.
Those AXS droppers have an external battery that'll need to be charged separately from the bike, but on a bike equipped with SRAM's Transmission derailleur it's hardwired to the bike's main battery. If the battery runs down to 0% charge the system will still provide enough power to keep the derailleur shifting for up to two hours. At that point you'd have a heavy, non-motorized bike to pedal home, but at least you'd be able to shift.Display
The Powertrain display integrates neatly into the toptube, allowing the mode, remaining battery level, and whether or not auto shifting is enabled (yes, there's an auto shift mode - more on that in a bit) to be seen at a glance. At the moment, there's no way to customize the information shown on the display – what you see is what you get. That stands in contrast to Specialized's Mastermind TCU display, which has 120 possible configurations, with options to show speed, time, elevation, range, cadence, and more. I'd imagine SRAM will add more features as time goes on, but it does seem fairly basic compared to the offerings from Specialized and Bosch. Auto Shift
Shimano debuted their latest e-bike auto shift system earlier this year, and now SRAM has developed their own system. This system keeps tabs on cadence, and automatically shifts to allow riders to keep spinning at the same RPM. There are seven differerent cadence settings that can be adjusted up or down by first holding the lower right shift button and then pushing the top or bottom button to adjust the pedaling speed the system will try to maintain.
Powertrain also has Coast Shifting, which, as the name implies, makes it possible to change gears while coasting and not pedaling. That can make it easier to set up for a technical climb, or to shift to a harder gear in order to accelerate out of a corner. Initial Impressions
I've been able to spend time on three different bikes equipped with a Powertrain motor, and in all instances the motor has worked well, quietly putting out enough power to get up ridiculously steep climbs, and remaining impressively silent on the descents. There's no clacking when you stop pedalling, and zero rattling when bombing down rough sections of trail, a refreshing departure from the noisier options already on the market.
Riders who have spent time on a Specialized Turbo Levo will find the experience to be very similar, at least as far as power delivery goes. It's a very natural pedaling feel, one that doesn't require much adaptation compared to a non-motorized mountain bike. Compared to Shimano's EP8 motor, the Powertrain doesn't require as high of a cadence to get the most out of the motor. That slightly slower optimum pedaling speed is especially beneficial on steep climbs, where it makes it easier to maintain a consistent level of power without pedaling frantically.
Although the numbers on paper give the Powertrain a slight edge when compared to Bosch's Performance Line CX motor, on the trail the Bosch motor feels more powerful – it packs more of a punch than the Powertrain, and it feels like it's providing more support on extra-steep climbs.
As for the AutoShift function, it does work, although not well enough that I'd want to go on a ride and not have the option to manually shift. I can see it being an interesting feature to enable on rides that involve a more consistent climb, but on punchy sections of trail it can struggle - remember, it's not predictive, which means that it can take a bit for it to adapt to the cadence change brought on by a sudden climb, potentially causing the rider to pedal in a harder gear than they'd want until it finishes shifting.
It's still early in the test period for the Powertrain – I'll be putting a bunch more miles in on a bike equipped with this motor. Stay tuned for a follow-up review after I've gotten in enough muddy miles.