Setting the wheel size on a Bafang 850C / 860C / 500C / 750C
Wheel size is under Information on the colour displays and is entered in inches. Set it once when you change tyres or fit the display to another bike.
Step by step
- Switch on, then press and hold + and − together (on a 860C with an M/i button: hold + and − as well, or press i twice on some firmware) for about 2 seconds until the Setting menu opens.
- Open Information and scroll to Wheel Size.
- Press power. If the value flashes, adjust with + / −. If the display asks for a password, enter 8018 digit by digit (see the password guide).
- Pick the ETRTO nominal size of your tyre: 20, 24, 26, 27.5, 28/700C or 29. Plus and fat tyres: choose one size up.
- Confirm with power, Back → Exit.
- Verify against GPS or a car speedometer over a kilometre; adjust one step if it reads more than 3 % off.
Can't find it?
If Wheel Size shows the right value but speed is still wrong, the controller has its own wheel size (BBS02/BBSHD via the programming cable, M-series via BESST). The display value only sets what you see; the controller value sets where the assist cuts off.
Frequently asked
What if my tyre size is not in the list?
Choose the closest circumference from the table. 27.5 × 2.8 = about 2250 mm, closer to 29" than 27.5".
Why is Wheel Size password-protected?
So riders cannot set 16" on a 28" wheel to fool the speed limit. 8018 unlocks it on stock Bafang firmware; OEM firmware may refuse.
Does wheel size affect the battery range estimate?
Yes slightly: range is computed from distance, so a wrong wheel size makes the estimate wrong by the same percentage.