EX1 is the world’s first drivetrain system specifically developed for e-MTBs

Designed from the ground up to offer a different gear range, bigger steps between gears and to better deal with the low-cadence high-torque pedalling typically done on e-MTBs.

Only recently we saw Shimano unveil their ‘XT for e-bikes‘ – E8000 – but this new offering from their rivals SRAM is much more of from-the-ground-up re-working of how an e-MTB gear system should work in their opinion.

Starting from scratch

As such, EX1 is the first and only drivetrain available today that was designed from the ground up specifically for E-MTBs. SRAM say that EX1 has been designed using information from motor manufacturers as well as SRAM’s own ideas of what the usual issues are with e-MTB gears.


As with SRAM’s other new drivetrains, it’s a single-ring affair with a large cassette. As well as the advantages mentioned above, the system also claims to be quieter, more durable and offer increased battery life over existing e-MTBs that use standard MTB drivetrains.


E-Block cassette

8 speed. 11-48T. Biased towards climbing gears (note lack of 10T sprocket). Allows for a 436% gear range. Big steps between gears – average of 30% (normal drivetrains are between 15-20% steps). Due to lack of 10T sprocket it fits on a normal freehub ie. non-XD driver.

Machined from case-hardened tool steel. Narrower than a 10- or 11-speed cassette which helps maintain a straighter chain line.

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SRAM state: “Cog architecture has been engineered to work with both inner and outer links of the chain, which allows extremely refined shifting for both inboard and outboard shifts.”

Sprockets: 11t, 13t, 15t, 18t, 24t, 32t, 40t, 48t.



Available with 14T, 16T or 18T X-sync narrow-wide direct-mount steel sprockets (for Bosch motors).

Isis bottom bracket compatibility. Designed specifically to work with Bosch and Brose “mid-ship motors” ie. motors around the BB.

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X-Horizon rear mech

Engineered to specifically handle high-torque, low-cadence shifting across the 11-48 tooth E-Block cassette. Clamed weight: 289g.

>>> Watch: We ride the SRAM XX1 Eagle 12 speed groupset


X-Actuation shifter

Single-shift at a time. Alleviates troublesome double shifting and over-shifting. Claimed weight: 122g.


EX1 chain

8 speed. The straighter chain line allows the use of a chain that is wider than those found on drivetrains not specifically engineered for e-MTBs.