The Performance CX is dead, long live the Performance CX. With a bang, the Performance Bosch the secret that had been rumoured on the internet for several weeks. To make things even more exciting, the Reutlingen-based company even ran a countdown on Facebook until the end of the embargo. Now the cat is out of the bag: Generation 4 is here, the new e-bike motor from Bosch. For five years, the successful "Generation 2" version of the Performance CX was installed thousands of times in a technically unchanged form and paved the way for sporty e-MTBs in the first place. The new "Generation 4" version is set to build on this success story and set new standards in terms of performance.
We have already had the opportunity to inspect and test the new e-drive extensively as part of an exclusive presentation with Bosch Ebike Systems boss Claus Fleischer and chief tester Stefan Schlie.
Smaller and lighter - the Bosch Performance CX in 2020 bikes
Even at first glance, the significantly slimmer and more compact design of the new Bosch CX drive is noticeable. It is said to have 50 per cent less volume compared to its predecessor, while the surface area of the side silhouette has shrunk by a whopping 25 per cent. Behind the bottom bracket, and this is the first ground-breaking innovation, Bosch has saved a lot of material. This finally leaves enough room for the bike designers to realise compact geometries with short chainstays. Even more impressive than the dimensions is the weight saving that Bosch has achieved with Generation 4: the unit weighs 2.9 kilos, making it a whole kilo lighter than its predecessor. With these values, weight and size, the new Bosch is now pretty much on a par with the Shimano Steps E8000. All in all, we can look forward to significantly lighter Bosch bikes with short, sporty geometries in the upcoming E-MTB generation for 2020.
No upstream gearbox, no internal resistance
A small part of the significant weight saving of the fourth CX generation comes from the use of various lightweight materials inside the motor. However, the lion's share comes from the elimination of the internal 2.5-speed gearbox between the crank and chainring, which was needed to drive the small sprocket at 2.5 times the speed. Bosch had integrated the control sensors of the CX into this gearbox - the means of choice given the state of the art at the time. Now, so-called "high-resolution" sensors for torque, cadence and acceleration pick up the information contactlessly at the bottom bracket axle and make the transmission superfluous.
However, the advantage of this 1:1 ratio is not only the weight saving, but above all the minimised internal resistance. Whereas with the previous generation you had to pedal the five upstream sprockets above 25 km/h or with the motor switched off, with Generation 4 you only move the bottom bracket axle - as with a classic bike. In addition, there are no losses due to the unfavourable, narrow wrap angle of the small drive pinion, which usually has 16 teeth. And the excessive wear of the small sprocket is also history.
The facts about the Bosch Performance CX Gen4
- Weight: 2.9 kilos, around one kilo less than its predecessor
- Significantly more compact than its predecessor
- New Powertube battery with 625 watt hours
- The internal 2.5-speed gearbox is no longer required, so there is no longer a small drive pinion
- No new displays and control units (Kiox and Purion are available)
"High-resolution" sensor technology brings better dosing capability
The low weight, the compact size, the direct transmission: all these technical advances were to be expected with a model change after five years. Bosch is now on a par with the Competition from Shimano, whose Steps 8000 motor presented these values two years ago. But even more important for the performance of an engine are the inner values such as response behaviour, modulation and dynamics. In short: How does the engine react to the pilot's pedal pressure? Engineers, test drivers and, above all, the boss himself have racked their brains over the years. And so the Bosch unit is packed with measurement technology: high-resolution sensors for speed, torque and acceleration measure the torque applied via the pedal 1000 times per second and read the rider's wishes from the pedal pressure, so to speak. In addition, a tilt sensor registers how steep the bike is in relation to the slope. The processor in the electric motor's black box processes all this information and provides the appropriate characteristics.
Maximum power over the predecessor model
The Bosch engineers have also tweaked the power. The new Performance CX drive is designed to provide 340 per cent support instead of 300 per cent. This means that with a pedalling power of 100 watts, the motor adds 340 watts in turbo mode. The maximum power should now also be in the region of around 600 watts. That would be 20 to 40 watts more than its predecessor. Bosch specifies the torque at 75 Newton metres, the same as the previous model.
More reach thanks to new Bosch battery
Bosch also has something new to report when it comes to the power supply. The flagship is a newly developed Powertube battery with 625 watt hours. The battery has been developed for integrated use. It has the same proven shape as the 500 watt hour Powertube versionwith which Bosch has already been offering bike manufacturers a fairly slim integration for two years. However, the new 625 version is slightly longer and naturally heavier. Bosch offers a total of three battery versions for the sporty segment: The two integrated Powertube batteries with 625 and 500 watt hours respectively, as well as the tried and tested top-mounted battery with 500 watt hours. The option of power supply from third-party manufacturers is still excluded. The weights of the batteries at a glance: Powertube 625: 3525 grams, Powertube 500: 2880 grams, battery pack 500: 2580 grams.
Bad news for e-bike tuners
Traditionally, Bosch has always been in the lead when it comes to the fight against e-bike tuning - too much is at stake for the entire sport if it is easy to open up the systems. "I like to be a spoilsport so that the game goes on for a long time," is CEO Claus Fleischer's motto. Fleischer is now putting his money where his mouth is. Special software recognises after a certain time when the system is tuned and then regulates the power back into an emergency mode. The biker can return the system to its normal state by riding in reduced mode for a further 90 minutes. However, if the software then diagnoses that the electric motor has been tampered with again, only the dealer's diagnostic tool can help. After three "tuning" attempts, however, this is also the end and the motor is irreparable. The golden age of Bad Ass Kit & Co. is probably over.
Bosch with Fox: The electronic suspension for E-MTBs is coming
It is obvious to utilise the battery, which is already available, for other integrations beyond its actual purpose, such as lighting. With the new Performance CX generation, Bosch, together with suspension manufacturer Fox, is paving the way for the integration of the Fox Live Valve on e-mountainbikes. The sensor system of the automatic, electronic suspension is located in the right fork leg, determines the ground conditions 1000 times per second and adjusts the damping of the suspension fork and shock accordingly. The system can be controlled via the Bosch Kiox display and the support level switch. Five settings from soft to hard are possible, while an automatic mode recognises certain riding conditions and automatically adjusts the compression damping of the fork. There is no need for extra batteries, as the energy comes from the Bosch system.
First test: How the Bosch Performance CX Gen 4 rides
Steep steps, slippery gravel tracks, hairpin bends - a test course couldn't be better. A challenging, technical single trail in the Zugspitz Arena served as a two-day course for us to extensively test Bosch's new generation of motors. The motor was installed in an unlabelled all-mountain bike with an integrated 625 Powertube battery, as well as in a Bosch test bike with an external 500 watt-hour battery.
The start is marked by a winding forest path: not too steep, but with a few tight bends and some short, root-covered ramps. I immediately switch to turbo mode, the most critical of all modes. With the current CX drive, it tends to be a bit rough, impetuous and jerky. Now I no longer feel any of this rough character. Although the motor pushes off with the usual pressure, it engages much more smoothly and responds immediately to a reduction in pedal pressure. I shift into a high gear and simulate lazy shifting. Curve after curve, the e-bike crawls up the trail. I deliberately try to avoid overdosing with the brakes. My legs alone are now dosing the thrust. I chirp through the tight bends at extremely low revs. That wouldn't have worked in the past. Now it's a step full of roots. I lift my bum out of the saddle, bend low over the handlebars and pedal for all I'm worth. The powerful boost lifts me one floor higher without any loss of traction - chapeau!
The trail branches off onto a flat gravel track. I get out of the saddle and accelerate, still in turbo mode. The Bosch motor never used to like that. It would have responded with unpleasant, almost eggy riding behaviour. Now it feels like I'm sprinting on a non-motorised bike, but with ten times as much power in my legs. This motor realises one-to-one what I demand of it. Without jerking, without delays and without the feeling of operating a machine. It's as if the bike reacts automatically to the rocky outcrop, the gravel section, the slippery root in front of me and I ask myself more than once: How does it know that?
On the flat, I test out the thread. The old feeling of driving into a wall is completely gone. The fact that the engine power stops at 25 km/h is hardly noticeable. I pedal as freely as with other leading motors in this discipline. And all those who have claimed that the inner resistance of the Performance CX is just a figment of their imagination are advised to find out better with the Generation 4. And last but not least: Our initial impression is that the new Bosch has become somewhat quieter. It clearly doesn't come close to the whispering sound of a Brose - but compared to its predecessor, we think we have recognised an improvement without having ridden both models in a 1:1 comparison.
Conclusion: The new Bosch Perfomance CX Gen4 sets a new benchmark in terms of riding performance, modulation and bike feeling. It remains to be seen how the lightweight e-bike motor performs in terms of stability and range. The results will be provided by the EMTB test benches on which the new e-drive will have to prove itself over the next few days. You can read all the test results in EMTB issue 3/19, on newsstands from 6 August!
