SRAM EX1 e-bike drivetrain review
SRAM’s EX1 drivetrain is highlighted by the 11-48 8-speed cassette with 30% jumps between gears.
Lowdown: SRAM EX1 E-Bike Drivetrain
The e-bike market for commuting and trail riding is growing at a rapid pace and new motor systems and frames designed for the task are being introduced every few weeks. Most of the current bikes use an existing 2×10 or 1x system for these bikes and they kind of work. But spend some time with one and you’ll realize that there is quite a bit of room for improvement.
The weak links are in shifting and braking. On an e-bike, shifting is always performed under more power than before and it is difficult to fully unload the drivetrain during shifting. So the system is put under a lot of stress and disturbing crunching noises and early demise of chains is often the result. The other area is braking since there is an extra 20 pounds of weight (and sometimes more speed) involved. SRAM sought out to provide a solution for both these issues with the EX1 component group. Read on to find out how it performed in this Mtbr test.
Stat Box
| Number of Speeds: 8 | Price: $941 |
| Gear Range: 436% with 11-48 cassette |
Rating:  5 out of 5 |
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Review: SRAM EX1 E-Bike Drivetrain
We rode the EX1 group for two months and performance was flawless. It never missed a shift, and even under power there was no hesitation getting on the biggest cogs.
Our test rig was a Haibike AMT Pro equipped with the latest CX Line motor from Bosch.
The true hallmark of this group is the cassette and the chain. SRAM realized early on that most cyclists have learned to ease up on the power when shifting since existing set-ups are not designed to shift under full power. On an e-bike however, the motor can double-down the rider’s pedal input, so even though the rider is only pedaling at 50 watts, the system can be another 100 watts of power. And on a very steep hill, combined power outputs of 500 watts can stress or blow up a 2×10 drivetrain while shifting.
And do you know that most riders double-shift? Normal shifts usually deliver a 15% jump and when that’s not enough, the rider will hit the trigger twice almost subconsciously both to upshift and downshift. This puts even more stress on an e-bike system.
The front of the cassette displays the forged steel rings with an alloy big ring. All are sculpted to provide controlled shift points.
EX1 solved these problems by using a shifting system derived from their Eagle 1×12 drivetrain. They use an extremely durable, forged cassette and they control the shift points with the cogs and the chain. On the big cogs, the chain is allowed to shift at four controlled points to ensure a smooth transition. They also made bigger shifts of 30% since that is more appropriate for an assisted rider who will be able to maintain cadence after the shift. And finally, they removed the double-shift ability from the shifter. The rider has to hit the shifter twice instead of just pushing hard to achieve a double shift. Does it work? Absolutely. Shifting during our testing was flawless.
Continue to page 2 for more of our SRAM EX1 e-bike drivetrain review »
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