Bosch Updates Top-of-the-Line Performance Line CX

Some products set the standard by which their category is judged. The Gibson Les Paul comes to mind. So does the Bosch Performance Line CX. When it was released in 2015—nearly ten years ago—the Performance Line CX was the first system dedicated to eMTBs. Since then, it has become the go-to mid-drive motor for electric mountain bikes, the motor against which all others are judged. It’s hard to believe that nine years have passed since Bosch introduced the Performance Line CX, considering how quickly the e-bike market moves.

When Bosch set out to redesign the Performance Line CX motor, they chose to keep the basic performance parameters the same: The motor still produces a maximum of 600W and up to 85Nm of torque, making for a 340 percent assist. The question, of course, is why Bosch didn’t increase the amount of assistance. In Bosch’s view, the Performance Line CX already provided the perfect balance of power, rideability, efficiency relative to battery range and drivetrain durability. More power would mean greater weight, making the eMTB heavier and less nimble; it would also result in a decrease in range because of more weight and drawing more power for the motor, as well as more wear and tear on drivetrain components.

So what changes? Well the first notable difference is that the new motor is 100g (3.5 oz.). The new motor also provides greater thermal stability; traditionally as a motor heats up, power production is reduced by the controller to prevent the motor from overheating. While the previous Performance Line CX offered greater thermal stability than its competitors, the new motor shows even more consistent performance on long rides.

Bosch redesigned the different sensors to make it even more responsive to rider input. It features new torque and cadence sensors, as well as the addition of inertial sensors. The inertial sensors measure acceleration in three axes as well as rotation in three axes—six sensors total and what this does is provide the controller a sense of where the eMTB is in space—how it is moving. The motor can now respond in subtle ways based on whether the rider is climbing, descending, riding on smooth ground or rolling through a rock garden or over roots.

Bosch has cut the amount of noise the motor produces, particularly the higher frequency sounds that tend to be the most noticeable part of the sound a motor generates.

The Performance Line CX now offers a smart walk assist; with the press of a button, the rider receives just enough power to walk up grades too steep to ride, but thanks to the inertial sensors, it tailors the speed of the walk assist based on the grade and how smooth or bumpy the ground is. They’ve also added a hill hold feature, which will provide just enough power to keep the eMTB in position for 10 seconds after releasing the walk assist button. Additionally, they’ve added hill start assistance for when the trail is so steep that it is hard to generate enough speed and balance so that you can move the foot that’s on the ground to the pedal. Hill start assist provides an extra burst of power so that the rider can get up to a balancing speed and land their foot on the pedal.

Extended boost features new software that reads how quickly or slowly the rider is pedaling and that informs how long the boost is—the slower each pedal stroke, the longer the boost.