The robots are coming for your mountain bike drivetrain. Today Shimano announces the latest EP6 motor and an update to the EP8 that integrate with updated Di2 rear derailleurs to offer the ability to shift without pedaling, and also automatic shifting (if you want it). Here’s what we know so far about how the system works.
Shimano FREE Shift
Like some of the gearbox and geared hub drivetrains on the market, the new Shimano integrated system allows riders to shift gears without advancing the pedals. Unlike those systems, the Shimano drive system works with a traditional 11- or 12-speed cassette. The magic is possible thanks to the electric drive motor working in concert with a Di2 electronic derailleur. When the rider presses the shift button the drive motor advances the chain (though not the crank arms) and adjusts the derailleur, allowing for shifts while cornering, for example.
Shimano AUTO Shift (with Manual Override)
With the motor and derailleur talking to one another (plus integrated wheel speed and cadence sensors), the Shimano drive system can automatically shift for the rider. This is said to work for both climbing — where the system would presumably move into easier gears to keep pedal cadence up — and descending. On descents the system detects when the rider is coasting and shifts the chain onto a smaller cog. The video below illustrates how this is supposed to work.
Shimano makes it abundantly clear in their marketing materials for this new feature that it can be manually overridden, and that riders don’t have to run automatic shifting if they don’t want to. This suggests auto shifting may take some getting used to, or perhaps that it’s not completely foolproof yet. At the very least it seems there may be some tradoffs to automatic shifting, especially on the trail, though we won’t know for sure until we’ve had a chance to try it for ourselves.
E-bike only features
Because FREE and AUTO shift rely on a motor at the crank end of the drivetrain, these features are limited to e-bikes only. The new EP6 motor and an updated version of the EP8 are required, as is an eMTB-specific Di2 derailleur. (The new Di2 LG is an 11-speed derailleur, while the Di2 HG+ is a 12-speed derailleur.) The motor and derailleur will need to be purchased together since they work as a system and Shimano says for now, the combo will only be available to consumers who purchase new bikes with the components installed.
EP6 motor comes to MTB, promising a lower price point
Until now Shimano 6-level motors have only been available for commuter bikes. The new EP6 is a dedicated mountain bike motor that’s offered at a “mid-level” price point compared to the EP8 and EP7 models. Shimano says the EP6 delivers 85Nm of torque just like the EP8.
The EP8 gets a minor tech update to work with the new derailleurs as well, and the updated model is designated EP801. The EP801 shaves about 300g off the weight of the EP6 while delivering the same torque and 250W of continuous power.
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