Home › Display settings › Bafang C961 / C965 (older BBS displays) › Bafang C961 / C965: set wheel size
Setting the wheel diameter on a Bafang C961 / C965
Wheel size is the third settings item and is entered in inches (16–29, 700C). It corrects the speed and distance readout.
Step by step
- Switch on, then hold + and − (up and down on the C961) together for about 2 seconds until the settings screen appears.
- Press power briefly twice to skip Backlight and Unit.
- Wheel size flashes. Set it with + / − to the tyre's nominal size.
- Press power to move on; continue to Exit and confirm, or hold power 1 second to save.
- Ride a known distance and compare.
Tip: Circumference reference (ETRTO tyre on a normal rim): 20" ≈ 1590 mm, 24" ≈ 1910 mm, 26" ≈ 2075 mm, 27.5" (650B) ≈ 2150 mm, 28" (700C) ≈ 2200 mm, 29" ≈ 2300 mm. Fat or plus tyres add 60–120 mm; a roll-out measurement (mark the tyre, roll one full turn, measure) beats any table.
Can't find it?
On some C965 firmware wheel size is locked and shows a '−−'. That is the OEM lock; the published code 8018 in the Advanced menu (hold + and − again from the settings screen) unlocks it on stock Bafang firmware only.
Frequently asked
700C or 28?
Same thing on this menu.
Why does speed read low after a fat tyre?
Bigger circumference; go one size up.
Does the controller need the same value?
On BBS01/02 the controller has its own; the display value only affects the readout.
Manuals and video
Videos found on YouTube and checked automatically; they are other people's work, not ours.
Other Bafang C961 / C965 (older BBS displays) guides
Bafang C961 / C965: switch km/h and mphBafang C961 / C965: 3, 5 or 9 levelsBafang C961 / C965: speed limitBafang C961 / C965: password and 8018Bafang C961 / C965: backlight brightnessBafang C961 / C965: lights
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.