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Setting the wheel size on a Tongsheng TSDZ2 VLCD5, VLCD6 or XH18

Tongsheng TSDZ2 VLCD5 / VLCD6 / XH18

Wheel size is in the settings list in inches (16–29, 700C). On the TSDZ2 the display sends it to the controller, so it affects both the readout and the assist cut-off.

Step by step

  1. VLCD5 (4 buttons): switch on, then press and hold the i (mode) button for about 3 seconds until the settings list appears. VLCD6 and XH18 (3 buttons): hold + and − together for 2–3 seconds. Menu layout differs by firmware, so navigate by the item names below.
  2. Step to the wheel size item (shown as a number with a wheel icon on the VLCD5/XH18, 'Wheel' on the VLCD6).
  3. Set 20, 24, 26, 27.5, 28/700C or 29 with + / −.
  4. i (or power) moves to the next item; + / − change the value; hold i (VLCD5) or + and − (VLCD6/XH18) to save and leave.
  5. Compare with GPS over a kilometre.
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. The TSDZ2 speed sensor is a spoke magnet: one pulse per turn, so there is no magnet-count parameter to worry about.

Can't find it?

Speed reads 0: the spoke magnet has drifted more than 3 mm from the sensor on the chainstay, or the sensor cable is cut (common on the TSDZ2). Speed reads 5 % off: wheel size. Wheel size item missing: dealer-locked firmware.

Frequently asked

27.5 not offered?

Use 26 or 700C, whichever roll-out is closer, or move to the open-source firmware.

Does wheel size change the cut-off speed?

On the TSDZ2, yes: the controller uses the display's value.

Fat tyre 26 × 4?

Set 27.5 or 28; the roll-out is around 2250 mm.

Other Tongsheng TSDZ2 VLCD5 / VLCD6 / XH18 guides

Tongsheng VLCD5 / VLCD6: switch km/h to mphTongsheng VLCD5 / VLCD6: assist levelsTongsheng VLCD5 / VLCD6: speed limitTongsheng VLCD5 / VLCD6: walk assistTongsheng VLCD5 / VLCD6: lights and backlight
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.