Home › Display settings › S866 / S830 / S861 LCD (generic hub-motor e-bikes, Fiido, Engwe, Himiway etc.) › S866 / S830: wheel diameter (P06) and speed magnets (P07)

Setting wheel size on an S866 / S830 / S861 display so the speed and distance are right

S866 / S830 / S861 LCD (generic hub-motor e-bikes, Fiido, Engwe, Himiway etc.)

Wheel diameter is P06, entered in inches to one decimal. P07 (number of speed-sensor magnets per wheel turn) must match too, or the speed is a whole multiple out.

Step by step

  1. Switch the display on. Press and hold + and − (up and down) together for about 2–3 seconds. On most bikes a password screen appears: enter 1919 (set each digit with + / −, confirm with power). If 1919 is refused, try 0512, 0000 or 8018. The parameter list then opens at P01.
  2. Press power until P06 shows. Set the diameter in inches with + / −: 20.0 for a 20" folder or fat bike, 26.0, 27.5, 28.0 (700C), 29.0.
  3. Press power to P07. Set the number of speed pulses per wheel turn: 1 for a spoke magnet and external sensor; for hub motors that use the motor's Hall sensor it is the number of magnet pole pairs (typical 20–23 for direct drive, 6 or 8 for small geared hubs). If unsure, leave what the factory set.
  4. Power (short press) moves to the next parameter; + / − change the value; hold + and − together to save and exit.
  5. Compare with GPS over a kilometre. 5 % off: adjust P06 by half an inch. 2×, 3× or 20× off: P07.
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. P06 accepts decimals, so 20" × 4.0 fat tyres (roll-out ≈ 1990 mm) are best set as 24.9 rather than 20.

Can't find it?

Some OEM firmware hides P06/P07 (they show but cannot be changed) so the speed limit cannot be cheated. Then the only fix is the brand's service tool. Speed shows 0 permanently: not a wheel-size issue, see error codes for the speed sensor.

Frequently asked

Fat bike shows 20 % too low?

The 4" tyre makes a 20" wheel roll like a 25". Set P06 = 25.0.

What is P18 speed ratio?

A percentage fudge factor (50–150 %) applied on top of P06/P07. Leave it at 100 and fix P06 instead; a P18 above 100 makes the bike hit the limit later, which is illegal tuning.

Why does my Fiido show 26 when it has 20" wheels?

Fiido firmware uses a fixed internal value on some models; the P06 number is then cosmetic.

Manuals and video

These displays are sold unbranded by many factories, so there is no single official manual. Check the manual that came with your bike, or your bike brand's support page.

Videos found on YouTube and checked automatically; they are other people's work, not ours.

Other S866 / S830 / S861 LCD (generic hub-motor e-bikes, Fiido, Engwe, Himiway etc.) guides

S866 / S830: change mph to km/hS866 / S830: assist levels (P05) and PAS parametersS866 / S830: speed limit (P08)S866 / S830: settings password (1919, 0512)S866 / S830: backlight (P01) and auto-off (P04)S866 / S830: walk assist and cruise (P17)S866 / S830: set battery voltage (P03)S866 / S830: throttle on/off (P10, P09)S866 / S830: trip and ODO reset (P16)S866 / S830: language
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.