Everything about the Bosch CX Motor

The Bosch CX motor was the trailblazer for the EMTB trend in recent years. While the Bild-Zeitung might call it a “motor for the people,” we remain slightly more reserved about its current development. The Bosch CX motor is still solid, but it now faces strong competition.

The Bosch CX, weighing in at 2.9 kilos, isn’t among the lightest motors. Additionally, it hums relatively loudly when you demand power from it, and rattles noticeably while rolling over the trail. Furthermore, its large build size detracts from the aesthetic appeal of many EMTBs. With the exception of the Mini Remote, the control elements from the Bosch peripherals often have the charm of a cordless screwdriver. Here, Bosch opens flanks that have been ruthlessly exploited by competitors recently.

Current bikes feature the Bosch Performance Line CX Motor of the 4th Generation. This motor is often abbreviated in product data by manufacturers simply as “Bosch CX Gen 4”. Unlike its predecessors, this motor no longer has a small sprocket always driven through a gearbox but a large chainring with 28 to 38 teeth. With the 4th generation, Bosch has addressed a major pain point. Above the support limit of 25 km/h, you no longer have to pedal against the resistance of the gearbox. This was still the case with the previous Gen 3, 2, and 1 versions.

Additionally, the build size has been reduced compared to previous motors, and the motor control has been significantly improved. The Bosch CX Gen 4 has outgrown its initial teething problems. At Eurobike 2024, the leading trade show in the bicycle industry, the 5th generation of the Bosch CX motor was already seen behind closed doors. Bikes with the new Bosch CX Gen 5 are expected to be delivered in Fall 2024. The build size has been reduced even further, and if Bosch did their homework, the motor is likely to be significantly quieter. The sound of the current Bosch motors is one of the biggest drawbacks.

Conversely, the introduction of the new Bosch CX Gen 5 motor also means that anyone who buys a bike with the Bosch CX Gen 4 motor is knowingly buying an “old” motor. The resale value of such a bike will drop significantly by 2025 at the latest, and you will also have to forgo some advancements.

The most widely used Bosch motor by far is the CX. However, Bosch also offers Full Power variants. For example, there’s the significantly more affordable Bosch Active Line motor. For sporty riders, there’s also the CX Race Edition. The Active Line motor was primarily designed for urban use and essentially has no place on sporty eMTBs.

The Race Edition of the Bosch CX motor, on the other hand, was specifically developed for riders who want to squeeze a bit more fun out of their bikes on the trails. Although the motor has an identical torque of 85 Newton meters compared to the regular CX motor, it is slightly more heat-resistant thanks to special cooling fins. Additionally, it features a powerful race mode and is slightly lighter than the regular CX motor. Overall, the Bosch Performance Line CX Race is a motor for a very specific audience hungry for performance.

In principle, Bosch motors can only be combined with Bosch batteries. Other manufacturers like Shimano are much more open in this regard. The PowerPack batteries mounted on the down tube from Bosch are rarely seen in the sporty sector anymore. Instead, more and more bikes come with batteries integrated into the down tube. This battery line is called Bosch PowerTube. Whether the battery can be removed from the down tube or not depends on the bike manufacturer’s design. Bosch offers the possibility for this, but the manufacturer must also utilize it.

The PowerTube batteries are available with 500, 625, or 750 Wh capacity. Weighing between 3 to 4.3 kilograms, they are relatively heavy compared to more modern batteries from DJI or Orbea. Other manufacturers also manage to pack a comparable energy value into smaller batteries. Bosch batteries are solid and withstand many charge cycles, but technically speaking, they don’t quite represent the latest state of the art.

When it comes to controls, Bosch is getting better and better. However, for a long time, their displays and switches reflected Bosch’s background in DIY tools. The often very large plastic elements usually don’t blend seamlessly into the design of modern EMTBs. The commendable exception is the Mini Remote, which does away with a display and cables altogether and keeps it as minimal as necessary.

What is still lacking in the entire Bosch periphery, however, is a small, discreet display that conveys the most necessary information. Even the Kiox 300 is relatively large and can hardly be mounted in a well-protected place. The Kiox 500 display is so large that protected mounting is not possible.

Many EMTBs with Bosch motors now come completely without a display. This is the final consequence of the currently somewhat inconsistent portfolio in this area. Thus, information about range or speed is not available. The battery status can only be read on the LEDs of the control center built into the top tube. A minimalist, but not a bad solution.

Besides the Bosch CX, the Shimano EP801 Motor is certainly one of the most widespread EMTB drivetrains. It has similar sound levels and performance figures. Its advantage: It is slightly lighter and can also be powered by third-party batteries. Brose has long been announcing a new motor but currently only has the Drive Mag-S motor, which is slightly more powerful than the Bosch CX and particularly much quieter. However, its belt drive occasionally causes issues in practical tests. The Sram Eagle Powertrain is also based on Brose hardware.

Newly introduced competitors like the new ZF Motor or DJI Avinox Motor, on the other hand, represent the next evolution stage among Full Power EMTB motors. They are becoming stronger, smaller, and lighter. A Full Power motor from TQ and Porsche is also expected soon, which will fuel these trends. The table below lists the data of the most important motors for orientation.