Unlocking Bosch Gen 4 (Performance Line CX 85 Nm): 2026 Guide
The Bosch Gen 4 Performance Line CX is the best-loved motor in the eMTB world: since 2020 it has powered a huge number of premium bikes, with up to 85 Nm of torque. That's exactly why it's also the system where advanced configuration makes the most sense. In this 2026 guide we look at how it works and how to be sure your Gen 4 is the compatible one.
What Bosch Gen 4 is
The fourth generation, and the Performance Line CX in particular, is powerful and has become the standard on electric mountain bikes from 2020 onwards. It pairs with the Kiox, Nyon and Purion displays.
Watch out, though: under the "Gen 4" name there are two different worlds, and that makes all the difference.
BES2 or Smart System? This is the key question
Take a look at the charging port on your eBike:
- Round port (BES2) → this is the "classic" Gen 4: you need the Bosch eBike Gen 1–4 Code (€69.99) ✅
- Oval magnetic port → this is a Smart System (BES3): a new architecture, so you need the Bosch Smart System BES3 Code (€179.99), not this one.
This simple check stops you buying the wrong code. The two codes are not interchangeable and digital codes are non-refundable once delivered. If in doubt, check for free with the Velocodix app or write to us at info@velocodix.it with a photo of the display and one of the port.
Why it's limited to 25 km/h
The CX motor performs far beyond that, but as standard it stops assisting at 25 km/h because of European regulations. Advanced configuration acts on that threshold and frees up assistance beyond it.
How the code works
- Software only, with no dongles or chips to install.
- Instant delivery by e-mail with a step-by-step guide.
- Activation over a Micro-USB cable, connecting the eBike to your PC (a data cable, not a charge-only one).
👉 The code is here: Bosch eBike Gen 1–4 Code
Speed on the display
After configuration, on Gen 2–4 systems the display reads roughly half the real speed. That's the normal behaviour of Bosch firmware in advanced configuration, not a fault: the motor's push stays fully intact.
Frequently asked questions
What's the top speed?
It depends on your gearing and wheel size: the motor assists beyond 25 km/h, with no fixed figure guaranteed.
Is my CX a BES2 or a Smart System?
Round port = BES2 (Gen 1–4 code). Oval magnetic port = Smart System (BES3 code).
Do I need to take anything apart?
No, it's all software: you connect the eBike to your PC with a Micro-USB cable.
What if I buy the wrong code?
Digital codes are non-refundable once delivered: that's why checking beforehand is free and takes two minutes.
Legal notice
In Europe, eBikes are type-approved with assistance up to 25 km/h. Configurations beyond the limit are for private land only and can affect the warranty, insurance and type-approval. Velocodix is not liable for any use that does not comply with local regulations.
In short
The Gen 4 Performance Line CX is the ideal candidate. The golden rule: check the charging port (round = Gen 1–4 code), keep the halved display reading in mind, and you're ready to go.
👉 Bosch Gen 1–4 Code · Check compatibility for free · Which Bosch code to choose