SRAM · SRAM Eagle Powertrain (Brose Drive S Mag derived)

Eagle Powertrain

SRAM's first e-MTB drive isn't really SRAM's at all: it's a Brose Drive S Mag in a new suit, retuned for the quietest, most natural-feeling power delivery in the class and wrapped around Eagle Transmission's Auto Shift.

Indicative only (no published dyno trace). Strong torque arrives early and the broad power plateau holds from the mid-60s through the high-80s before tapering smoothly at high cadence; the curve is modelled on SRAM's 90 Nm / 680 W claim, not a measured test.

The verdict

SRAM Eagle Powertrain is SRAM's clever shortcut into the motor game. Rather than spend years designing a drive unit from scratch, SRAM took the proven Brose Drive S Mag (the same hardware Specialized built its Levo around) and poured its effort into the software, battery, AXS pods, Bridge display and the Auto Shift integration with Eagle Transmission. The result is a 2.9 kg unit that SRAM claims makes 90 Nm and up to 680 W of peak power in Rally mode, with a tamer Range mode capped around 400-540 W.

No magazine has put it on a dyno and published a wattage: Velomotion, who measured peak power on their test bike, would only say it "sits pretty much between the Bosch CX and the Shimano EP8," and BikeRadar rate Rally as "almost identical in feel to Specialized's Turbo, but slightly down on power compared to Bosch's eMTB." So treat 680 W as SRAM's claim, not an independent result. What everyone agrees on is the delivery. Velomotion rated the Propain Ekano test bike among the quietest e-MTBs they had ridden in months, a soft hum rather than the old Brose belt whine, and the assistance builds progressively into that 90 Nm rather than slamming it into the rear wheel.

It is not the lightest or the punchiest unit out there, and the smooth tune means it never feels explosive: BikeRadar are explicit that Bosch's Tour+ and eMTB modes still lead on raw power. But for riders who want a drive that disappears beneath them, the Eagle Powertrain is one of the most refined-feeling motors money can buy, and the Auto Shift trickery is genuinely useful on technical climbs.

“A Brose in a new suit, retuned for the quietest, most natural power in the class.”

Character

Rider input

SRAM does not publish a single support multiplier. There are two factory modes: Rally (maximum, roughly 85% support in default tune) and Range (battery-saving, capped around 400 W / ~35% support in factory settings). Both are fully tunable in the AXS app up to 100% / 540 W, so a class-leading three-figure assist percentage (as a Bosch CX quotes) does not apply here. Push gently and assist ramps in progressively; the tune rewards smooth, measured pedalling rather than a hard surge of rider input.

On the trail

Smooth, progressive and unflustered: thrust builds rather than hits, giving a planted, natural pedalling feel that flatters technical climbs more than it thrills with raw punch.

Noise

No dBA figure has been published, so the "quietest in class" billing is a listening verdict rather than a measurement. Velomotion called their Propain Ekano test bike one of the quietest e-MTBs they had ridden in months. BikeRadar, comparing directly, heard zero freewheel clack or rattle and a steadier whirr than the Shimano EP8's fluctuating warble, similar in character to a Bosch Performance Line CX but lower in tone.

Efficiency

Range mode caps assistance around 400-540 W to stretch the 630 or 720 Wh battery (BikeRadar managed 1,800 m of climbing on a 720 Wh pack with 15% left), while the belt-and-clutch Brose driveline is efficient but adds the typical small Brose drag when freewheeling above the cut-off.

The case for and against

Strengths

90 Nm claimed on a proven, reliable Brose Drive S Mag platform
Among the quietest motors in the class (no rattle, steady whirr)
Smooth, natural, progressive power delivery
Eagle Transmission Auto Shift / Coast Shift integration
Over-the-air tuning via the SRAM AXS app
Well-sealed magnesium housing

Compromises

Heavier than a Shimano EP801 at 2.9 kg (plus ~3-4 kg of battery)
Smooth tune lacks the outright punch of Bosch's top CX modes
Slight Brose freewheel drag above the assist cut-off
Only two ride modes (Range / Rally), and no published dyno data

How it stacks up

On paper the Eagle Powertrain's 90 Nm tops both its obvious rivals by 5 Nm: the Bosch Performance Line CX (85 Nm, ~340% support, four modes) and the Shimano EP8/EP801 (85 Nm, up to 400% support, ~2.6 kg). No dyno has ranked their peak wattage, but Velomotion place the SRAM's measured peak power between the two. It can't match the outright drama and class-leading top modes of the Bosch CX, which BikeRadar still rate as the one to beat on raw power, nor the lightness of the EP801, but it is quieter and more natural-feeling than either. Its trump card is integration: the Eagle Transmission Auto Shift and Coast Shift, plus over-the-air AXS app tuning, are things neither rival's motor offers.

Sources: Velomotion (trail test, measured peak between Bosch CX and EP8) · BikeRadar (review, modes / noise / Bosch comparison) · BIKE Magazin (lab & trail test) · SRAM (manufacturer, 90 Nm / 680 W output statement) · SRAM Eagle Powertrain (manufacturer, batteries / range extender).