The Bosch Performance Line CX is the stalwart amongst eMTB motors. Now in its fourth generation, the compact and powerful motor can be found on a raft of bikes and vies for eMTB market dominance against Shimano. With battery capacities of up to 1,250 Wh, 85 Nm torque, a progressive eMTB mode and a low weight, on paper it ticks all the boxes. Is the hype for the Performance Line CX Gen 4 justified?

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This motor is part of our big e-mountain bike motor test. Click here for background information and the criteria of this test.

With 85 Nm torque, the Bosch Performance Line CX motor doesn’t just deliver plenty of torque but makes a convincing impression with its handling on the trail. Its maximum assistance level provides 340% support, meaning it can still stay on the tail of the higher-torque Brose Drive S Mag on steep slopes. The highlight of the 2.79 kg motor isn’t its power but its tuned eMTB mode. This dynamic and progressive setting varies the level of motor support between Tour (140%) and Turbo (340%), depending on the situation and how hard you’re pedalling. The motor almost always gets it spot on, delivering enough power while staying smooth and controllable. However, it can be a little too powerful or boisterous on level terrain for very lightweight riders. It would be nice to see the option to tune the motor support modes via an app, as is possible with Brose or Shimano. Thanks to Extended Boost, the eMTB mode recognises steps and obstacles, providing a powerful push and sustained support to get you over them. As a result, no other motor makes technical uphills as simple and easy to master as the Bosch Performance Line CX 2020! The transition at the 25 km/h assistance limit is also effortless for the Performance CX. Pedalling resistance? None at all! However, the new Bosch motor isn’t the quietest. We’re not talking about its relatively loud hum at full power but the clunk of the gearbox inside. The interlocking of the gears causes the Bosch motor to clunk metallically on almost all full-suspension bikes when the chain exerts force on the chainring as the suspension compresses.

Ready for any adventure
The DualBattery system offers up a 1,250 Wh capacity. The frame has to be designed specifically for that purpose though.

As is typical for Bosch, bike manufacturers are faced with an almost closed system and have to use Bosch’s own app and components including remote, display, batteries and standard motor tune with the Performance CX. The DualBattery option consisting of an internal PowerTube and external PowerPack makes a total battery capacity of 1,125 Wh possible. With two PowerTube batteries that can be stretched to 1,250 Wh. Despite offering six display options, it’s only Bosch’s Purion, Kiox and Nyon displays that are suited to eMTBs. With it’s sleek but small display, the Kiox is hard to read on the trail and the standard position on the stem isn’t ideal for aggressive eMTBing. The Purion display with its integrated remote is easy to use and offers all the most important information you need. However, compared to Shimano’s equivalent compact offering, it feels dated and clunky. The new Nyon display is well suited to tours and treks. Its 3.2” touch display offers standalone offline navigation and can match the length and elevation profile of planned routes to the remaining battery. Individual tuning of the support modes isn’t on the cards for either eMTBers (via an app) or dealers. Bike manufacturers have a bit more leeway and can contribute to individual modes and set the eMTB mode to match your crank length.

Exposed
The standard mount places the Kiox display on the stem, where it’s exposed to damage. That’s why most bike manufacturers have developed their own solutions here.
Touring pro
The Nyon display is currently the only ebike display that offers standalone offline navigation as well as range-based route planning based on the battery and elevation profile of the route.

In terms of weight and dimensions, the Bosch motor plays right at the top of the field, where it’s basically the definition of “light and compact.” This means bike manufacturers have a lot of flexibility as to how they want to shape the rear end of their bikes, though the prominent corner at the front of the motor housing creates some challenges for visual integration – at least if you want to fit the motor without a cover. There are also some issues remaining with the speed sensor. Bosch still offer only one model which relies on an unreliable spoke magnet. That’s why several manufacturers have developed their own solutions here, just like they have for the charging port.

Our conclusion

In terms of riding performance, the Bosch Performance Line CX 2020 is top class! eMTB mode is powerful yet intuitive to control, making it the best progressive mode currently available on the market. The new Nyon display is a particular highlight for tours and trekking riders. However, customisable assistance modes, a solution to reduce the metalling clunking and a minimal display/remote unit are still issues waiting for a solution.

Tops

  • compact and lightweight
  • phenomenal eMTB mode
  • simultaneously powerful and easy to modulate
  • Nyon display for tours and trekking

Flops

  • clunking of the internal gears
  • challenging integration (display, remote, sensor)
  • no custom support modes

For more information head to bosch-ebike.com

This motor is part of our big e-mountain bike motor test. Click here for background information and the criteria of this test.

Brose Drive S Mag | Bosch Performance Line CX | FAZUA Ride 50 Evation Firmware 2.0 | SACHS RS | Yamaha PW-X2 | Shimano STEPS E8000 | Shimano EP8 | TQ HPR 120S | Specialized SL 1.1


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Words: Felix Stix Photos: E-MOUNTAINBIKE team

About the author

Felix Stix

Felix is chief of testing and undoubtedly one of the best test riders in the world. With a degree in sports engineering, excellent mountain bike skills, his love of technology and as a certified bike guide, Felix has everything it takes to make comprehensive and fair assessments of bikes. His legendary group tests are internationally known and feared, though they tend to be a bit longer due to his love of detail and technical deep dives. Every year, he reviews around 100 bikes, specialising in the subject of tires, motors and suspension, before putting on his skis come winter! His know-how is incorporated into each of our reviews, ensuring the quality of our work stays high!