It was only a matter of time, but Shimano have now announced that the STePS power assist system will now be available on mountain bikes too. The new components will be available from October 2016.
Shimano's STePS urban/leisure components launched in 2013, and they're now specced on a wide range of bikes. Shimano have been missing out in the mountain bike market, however, which has been dominated by the Bosch Performance Line CX motor. The E8000 STePS components are a direct competitor to that system, and you'll most likely see them on bikes from just under £2,000 upwards in 2017.
The E8000 drive unit has been designed to be lightweight and compact, with a lower Q-factor (the distance between the cranks) so that the feel is more like a standard mountain bike. It delivers 70Nm of torque, just under the Bosch motor's maximum of 75Nm but well above the 50Nm the curent E6000 motor delivers.
Unlike the Bosch motor, which uses a small drive sprocket, the STePS motor features a 34T or 38T sprocket (with optional chain guard). There are hollow and solid crank arms available, with a premium for the lighter hollow units.
The power for the motor comes from a 500Wh battery, the same capacity as the larger batteries from the likes of Bosch and Giant. That should give you enough range for a good few laps of the trail centre. There's three assistance modes (Eco, Trail and High Power) and a power walk mode for moving your bike about.
The system has a new colour LCD computer. Unlike most displays which stick out in front, this one is designed to sit behind your bars, where it's a bit more protected. You'll get the normal battery level, range, power assist and speed info, plus gear number if you're running the STePS system alongside Shimano's Di2 electronic shiftgear. It can be used with mechanical gearing as well, of course. 10 and 11 speed drivetrains are supported.
The STePS mountain bike system will communicate via Bluetooth with Shimano's E-TUBE platform: you'll be able to change settings and customise your set-up from your computer, tablet or smartphone. It should make future firmware upgrades straightforward too.
The STePS E6000 leisure/commuter system has recently been upgraded to offer automatic shifting with Shimano's Di2-controlled Nexus and Alfine hubs. There's no word as to whether auto-shifting will also be available on the mountain bike system, although we suspect it's only a matter of time.