Bosch Kiox (BES2): wheel circumference (dealer-set, small correction possible)
Settings > My eBike shows the wheel circumference; some firmware lets you correct it a few percent, anything more is dealer-only via DiagnosticTool because it defines the 25 km/h cut-off.
Step by step
- Switch the Kiox on.
- On the status screen (press < on the control unit until you reach it), press the select button (centre of the control unit) to open 'Settings'.
- Go to 'My eBike' and confirm.
- Move to 'Wheel circumference'. The stored value is shown in mm.
- On firmware that allows it, press select and adjust with + / − within the permitted range (roughly ±5%); confirm with select. If the value is read-only, only a dealer can change it.
- For a real change (different wheel/tyre size) give the dealer the measured circumference; they set it in DiagnosticTool.
Can't find it?
If speed is consistently a few percent off, the circumference is wrong. If it jumps or shows zero while riding, realign the speed sensor and spoke magnet first (3 to 5 mm gap, magnet centred on the sensor).
Frequently asked
Why is the wheel circumference locked?
It determines the real speed at which assistance stops at 25 km/h. Bosch only lets dealers set the base value.
What does the ±5% correction do?
It fine-tunes displayed speed and distance; the assistance cut-off is not affected.
Does a wrong circumference cause error 503?
No; 503 is a missing/implausible speed signal, usually a sensor or magnet problem.
Manuals and video
- Bosch eBike Help Center: official error-code index
- Bosch eBike downloads: quick start guides and battery guide
- Bosch eBike dealer search (DiagnosticTool readout)
Videos found on YouTube and checked automatically; they are other people's work, not ours.