Tongsheng TSDZ2/TSDZ8 Installation Guide: Torque-Sensing Mid-Drive Conversion Step by Step

Expect a moderate-difficulty job that takes 3 to 5 hours for a first-time installer. Both the TSDZ2 and TSDZ8 are torque-sensing mid-drive motors that replace your bottom bracket and crankset, turning a standard bike into an e-bike where pedal effort directly controls motor power. The TSDZ2 is the older, more common model with an external controller box; the TSDZ8 integrates the controller inside the motor housing, simplifying wiring. This guide covers both, highlighting where the steps differ.

Tools and Parts Checklist

Tool / Part	Purpose
Crank puller (square taper or ISIS, matching your current cranks)	Removes existing cranks
Bottom bracket tool (spline or pin-style, matching your frame)	Removes existing bottom bracket
Cassette lockring tool and chain whip	Only if removing the rear wheel
Torque wrench (Nm range)	Critical for crank arm bolts
Allen keys: 4mm, 5mm, 6mm	General assembly
Flathead screwdriver	Removing dust caps and plastic covers
USB-ST-Link programmer (V2 or clone)	Required if flashing Open Source Firmware (OSF)
Tongsheng motor kit (motor, harness, display, speed sensor)	Main components
Battery (36V or 48V, matching your kit)	Power source
Throttle and brake levers (if included)	Optional controls
Marine or lithium grease	Bottom bracket threads
Blue threadlocker	Crank arm bolts

TSDZ2 extra item: A zip tie to hold the torque-sensor magnet ring in place during crank installation (explained later).

TSDZ8 advantage: No external controller box means fewer parts to route and no phase-wire matching.

Frame Check and Bottom Bracket Removal

Step 1: Remove the cranks. Use a crank puller. The left crank has left-hand threads (turn clockwise to loosen). The right crank is standard (turn counterclockwise). Keep the crank arms – you’ll reuse them with the motor, though the TSDZ2 and TSDZ8 often come with new arms.

Step 2: Remove the existing bottom bracket. Most modern bikes use a 44mm or 50mm spline tool. Older frames may need a pin spanner. Remove the drive-side cup first, then the non-drive cup.

Step 3: Measure the bottom bracket shell width. It must be 68mm or 73mm. Both motors fit these widths using included washers. Measure with a ruler or caliper – if the measurement is between these values, your frame is not compatible without adapters that add noticeable stack height. Check with a reputable e-bike conversion shop before buying.

Step 4: Clean and inspect the shell threads. Remove old grease and debris with solvent. If you see burrs or feel rough threads, chase them with a bottom bracket tap. This step saves hours of frustration later.

Step 5: Check frame clearance. The TSDZ2 motor housing is larger front-to-back – it can contact chainstays on frames with tight rear triangles, especially older steel bikes with steep angles. The TSDZ8 has a narrower housing (roughly 1.5 inches less forward protrusion) but a longer front section that can hit the downtube. Hold the motor cartridge in the shell without tightening and rotate it to verify clearance in all pedal and turning positions. If the housing contacts the frame at any point, do not proceed – forcing it will crack the motor casing.

Step 6: Set the cranks and bottom bracket aside. You will not reuse them.

Installing the TSDZ2 or TSDZ8 Motor

Mounting the Motor Casing

Slide the motor into the bottom bracket shell from the non-drive side (left). The wire exit port must angle toward the downtube – not forward toward the front wheel or downward toward the chainring.

For TSDZ2: The external controller box mounts on the right side of the downtube using the included bracket. Attach it loosely now. You’ll tighten it after routing wires.

For TSDZ8: No external controller. The main harness plug connects directly to the motor housing.

Insert the included bottom bracket cartridge from the drive side (right) and thread it in by hand. For a 73mm shell, use the supplied spacer. Tighten to 40–45 Nm. If the cartridge or motor housing wobbles after tightening, you need a different spacer combination – do not overtighten to fix misalignment.

Stop threshold: If the cartridge does not thread smoothly by hand for at least three full turns, stop. Do not force it. Remove the cartridge, check for debris or thread damage in the shell, and ensure the motor casing is fully seated. Attempting to force the cartridge will strip the frame threads, requiring a helicoil repair that a bike shop must perform. A stripped bottom bracket shell effectively kills your frame for this conversion.

Aligning the Torque Sensor

TSDZ2 alignment – critical step. The torque sensor consists of a magnet ring on the right crank arm and a sensor PCB on the motor housing. With the crank arm off, position the magnet ring so it faces the sensor squarely. The gap must be 1–2 mm – use a feeler gauge or a thin business card to check. Rotate the crank arm slowly by hand: the magnet must pass through that gap without touching any part of the housing.

Use the included spacer washer to adjust the gap. Common mistake: Tightening the crank bolt can pull the magnet ring out of alignment. Place a small zip tie around the crank spindle to hold the ring in place while you tighten, then snip the zip tie off afterward. If the sensor fails to detect torque during calibration, the magnet ring likely shifted – remove the crank arm and re-center it.

TSDZ8 alignment – skip this. The torque sensor is fully enclosed inside the motor casing. No manual alignment is needed.

Installing Cranks and Pedals

Apply blue threadlocker to all crank bolts.

TSDZ2 procedure:
– Right crank (drive side): install first using the small Allen bolt and washer. Tighten to 35–40 Nm.
– Left crank: attaches with two small bolts and a central dust cap. Tighten the two bolts to 6–8 Nm, then press in the dust cap.

TSDZ8 procedure:
– Both crank arms use a single Allen bolt per side.
– Left crank uses left-hand threads (turn clockwise to loosen, counterclockwise to tighten).
– Tighten both to 35–40 Nm.

Install pedals: right pedal clockwise, left pedal counterclockwise. Hand-tighten first, then use a pedal wrench for final torque.

Wiring, Display, and Battery Connections

Step 1: Speed sensor. Mount the magnet on a spoke and the sensor on the chainstay. Gap: 2–5 mm. The magnet must pass directly in front of the sensor’s marking line. A misaligned sensor will cause erratic assist cutouts because the controller loses crank rotation data.

Step 2: Display. Mount on the handlebar where you can read it while riding. Route the cable along the top tube or down the downtube, securing with zip ties. Connect to the main harness at the handlebar.

Step 3: TSDZ2 external controller wiring – most common failure point. The controller has three thick phase wires (yellow, blue, green) and five thin Hall-sensor wires (yellow, blue, green, red, black). Match colors exactly – yellow to yellow, etc. Reverse any single pair and the motor will vibrate violently under high current draw and may destroy the controller in seconds. Mark each wire with tape before connecting to avoid confusion.

Step 4: TSDZ8 wiring – much simpler. The main harness plugs directly into the motor’s integrated controller via a multi-pin connector. No phase wire matching needed.

Step 5: Battery connection. Connect the XT60 or Anderson connector from the battery to the motor harness lead. Confirm polarity: red to red, black to black. Most connectors have a physical key that prevents reverse connection. If yours does not, mark the wires with colored tape.

Step 6: Optional add-ons. Brake cutoffs, throttle, and lights connect to spare ports on the controller (TSDZ2) or the main harness (TSDZ8). Check your kit’s wiring diagram for exact pin assignments.

Flashing Open Source Firmware (OSF) – Optional but Recommended

Stock firmware on both motors delivers a sluggish torque response and jerky startup from a standstill. OSF smooths power delivery and lets you customize assist levels, startup power, and maximum speed. Flashing is safe if you follow the steps.

What you need: USB-ST-Link programmer (V2 or V2 clone, under $15), computer with USB, OSF firmware file for your motor.

Download and prepare: Get the latest OSF zip from the mbrusa or emmebrusa GitHub repository. Extract the binary and flash tool.

Connect the programmer: Install ST-Link drivers.

• TSDZ2 connection: Locate the 4-pin programming header on the external controller (pins: SWIM, GND, RST, SWCLK). Match SWIM to SWIM, GND to GND. If the tool reports “no target found,” swap the SWIM and GND wires – this is the most common flash hang-up.
• TSDZ8 connection: Remove the plastic cover on the motor casing. Locate the 6-pin header (SWD, VDD, GND). Connect programmer to SWDIO and SWCLK.

Flash the firmware: Run the flash tool, select the correct file (TSDZ2_8M or TSDZ8_x), and start. It takes about 30 seconds. After completion, disconnect the programmer and power on. The display should show a new version number.

Stop threshold: If the flash fails with “no target found” after swapping SWIM/GND, verify the programmer is firmly connected and the motor battery is disconnected. If it still fails, your programmer may be incompatible (clone quality varies) – try a different USB port or a known-good programmer. Do not attempt to flash with a partial connection, as it can corrupt the existing firmware and brick the motor until you reflash with a working setup.

Test and Calibration

Step 1: Spin test. Lift the rear wheel off the ground. Apply power and gradually increase assist. The motor should run smoothly with no grinding or vibration. If you hear unusual noise, stop immediately. On TSDZ2 builds, a violent vibration means a phase wire reversal – disconnect the battery and recheck wire order. On TSDZ8, a grinding noise could indicate a mechanical interference inside the motor casing (rare). In either case, if the issue persists after wiring verification, stop and contact Tongsheng support or your supplier – continuing could damage the controller or motor windings.

Step 2: Torque sensor calibration (required after OSF flash, recommended for stock firmware).
– Turn the system on.
– Position cranks horizontally (pedals at 3 and 9 o’clock).
– Press and hold the “up” button on the display until “CAL” or “CALIBRATE” appears.
– Pedal forward slowly with no load for about 10 seconds. The motor should not engage.
– After calibration stops, test: pedal forward with light effort. The motor should engage smoothly and proportionally. If the motor runs without pedaling, the torque sensor signal is inverted – swap two of the thin sensor wires (usually blue and yellow) and repeat calibration.

Step 3: Road test. Ride a short loop with a stop, a start from a standstill, and a moderate hill. Motor power should be smooth, with no surging or cutouts. When you stop pedaling, the motor should stop within one crank revolution. If there’s a delay, the torque sensor calibration may be off, or the speed sensor gap is too wide.

Common Installation Pitfalls and Fixes

TSDZ2 phase wire mismatch: Double-check color order before powering on. A reversed pair causes violent vibration and high current draw. If you see this, disconnect the battery immediately and re-check. Do not run the motor even briefly – it can melt the insulation on the wires.

Torque sensor magnet ring slip (TSDZ2 only): The ring can shift during crank installation. Use a zip tie to hold it in place while tightening. If calibration fails consistently, remove the crank arm and re-center the ring.

Cross-threaded bottom bracket cartridge: Always hand-thread for the first three turns. If you feel resistance, back out and re-align. Forcing it strips the frame threads. Stop threshold: If you cannot hand-thread after two attempts, do not proceed. The frame may have damaged threads or the wrong spacer combination – consult a bike shop.

OSF flash failure: As noted, swapping SWIM/GND often fixes “no target found.” If not, check programmer driver installation.

No display power: Check the battery’s main fuse first. Then verify the display cable is fully seated in the controller port. On TSDZ2, a loose connection at the external controller harness is common – push the connector firmly until it clicks.

Motor won’t fit the frame: If the housing contacts the chainstays or downtube, do not force it. The TSDZ8 fits tighter frames due to its narrower casing. If neither motor fits, your frame geometry is incompatible with mid-drive conversion. A hub-motor kit may be a better choice.

FAQ

Q: Can I install a TSDZ8 on a 68mm bottom bracket?
A: Yes. The TSDZ8 includes spacer washers that allow it to fit both 68mm and 73mm shell widths.

Q: Do I need to flash Open Source Firmware?
A: No, but stock firmware delivers a less natural torque response, with a noticeable delay on startup and a peaky power curve. Most owners flash OSF after installation because it dramatically improves ride quality.

Q: Why is my TSDZ2 not turning on after wiring?
A: First, check the phase wire colors – a single mismatch can trip the controller into protection mode. Next, verify the battery power connection and the display cable. On TSDZ2 builds, the external controller connector can also become slightly unseated when routing wires – push it in until you hear a click. If the display still shows no power, test the battery’s main fuse with a multimeter.

Explore This Topic

• Back to Motor and Power Output
• Back to E-Bike Motor Installation

Related guides in this cluster:
– Tongsheng Mid-Drive Motors: TSDZ2, TSDZ8, TSDZ16 & Torque-Sensing Conversion Kits
– Tongsheng TSDZ8 Motor Review: 750W Torque-Sensing Mid-Drive for DIY Power Builds
– Tongsheng TSDZ2 Motor Review: Budget Torque-Sensing Mid-Drive for DIY Beginners
– Bafang vs Tongsheng Mid-Drive Motors: Cadence Sensor vs Torque Sensor Showdown