How to update X35 / X20 firmware and what to do when the update fails
The X20 updates over the air from My SmartBike. The X35 updates in the app on newer bikes, but many X35 bikes need a dealer with the Mahle service tool for motor firmware.
Step by step
- Charge the bike above 50%.
- Connect the app to the bike; if an update is available, a banner appears on the bike screen, or check Settings > 'Firmware'.
- Tap 'Update' and keep the phone next to the top tube; keep the app in the foreground.
- The iWoc LED cycles colours during the update; do not switch off. X20 updates take 10 to 20 minutes.
- When finished, switch the bike off and on with the iWoc, then check assist levels and units.
- If it fails: switch the bike off for a minute, reconnect and 'Retry'. Persistent failure on X35: dealer.
Tip: X35 motors from 2017 to 2019 cannot be updated from the app at all; the app will just not show an update. That is normal, not a fault.
Can't find it?
No 'Firmware' entry: app out of date, or the bike is registered to someone else.
Frequently asked
Bike dead after an update.
Charge for an hour, then press the iWoc for 5 seconds. If still dead, dealer.
Do updates change assist?
On the X20, 2024 updates changed the assist profile noticeably; retune in the app.
What does the update fix?
Range estimation, Bluetooth stability and (X20) walk assist.
Manuals and video
Videos found on YouTube and checked automatically; they are other people's work, not ours.
- How to Update your Bike - MAHLE SmartBike Lab MAHLE SmartBike Systems
Other Mahle X35 / X20 (iWoc button, My SmartBike app) guides
Mahle: connect the My SmartBike appMahle: assist levels and customisationMahle: switch mph to km/hMahle: lightsMahle: walk assistMahle: speed limit
Still stuck? Take a photo of the display and show it to a local e-bike workshop. Bring the bike's system name (e.g. Bosch Performance Line CX) and the exact code; that saves diagnostic time and money.