Bosch's Performance Line CX motor system is already one of the most popular choices for pedelec e-mountainbikes, but a new firmware upgrade promises to make it even more intuitive out on the trails.
Called e-MTB mode, the new setting varies the amount of assistance the motor offers depending on how hard you're pedalling. That means it'll give you anywhere from 120% to up to 300% of assistance up to a maximum of 75Nm of additional torque. While those two figures tally with the existing fixed outputs in 'Tour' and 'Turbo' modes, it's actually the middle 'Sport' mode that will be dropped in favour of this variable output setting. That's largely because Bosch knows that the full throttle output of Turbo is what really helps sell e-MTBs when they're tested in the carpark, while Tour is an essential get-home setting when your battery is running low.
Bosch claims a number of rider benefits to e-MTB mode. As the assistance changes seamlessly in response to the input of the rider, it means you no longer need to fumble with a trigger to boost assistance to get over trail obstacles. Because sudden demands for power are dealt with by the motor rather than the rider having to get out of the saddle for a short intense effort, you can remain seated for longer, improving rear wheel grip on climbs. Bosch say that the fact that the power is progressively fed in results in a much smoother power delivery. That in turn leads to less wheelspin and (disappointingly for some) fewer wheelies, as when traction is lost the rider naturally backs off the pedals, assistance is reduced and grip returns.
The delay before assistance arrives is also reduced, making it much easier to get started, especially if you've stalled on steeper terrain. According to Bosch's head of e-bikes, Claus Fleischer, this was one of the most difficult things to achieve, requiring engineers to go deep into the software, with ride quality fine-tuning aided by the input of runner-up Trials World Champion Stefan Schlie.
This brings the Bosch unit more into line with what Shimano's STEPS M8000 mountain bike system offers in 'Trail' mode, where assistance is gradually added based on rider input. We haven't had a chance to ride a Bosch system with the new setting, but the assistance of the STEPS system is much less artificial feeling than the current Peformance CX motors.
New Performance Line CX units will come with this setting pre-installed from 1st July 2017, though it's also backwards compatible with 2016 or 2017 model year Performance CX units via a simple software update that will be offered free of charge from all Bosch dealers.
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