Bafang BBSHD Installation Guide

1. Step 1 of 6

   Measure and Prepare the Bottom Bracket

   Measure your bicycle bottom bracket shell width. The BBSHD comes in specific spindle lengths (68mm-73mm, 100mm, or 120mm). Remove the pedals, cranks, and bottom bracket cartridge using your BB tool. Thoroughly clean the bottom bracket shell interior and clean off any excess weld slag or paint threads.

   Schematic FIG. 1DIYPEV Technical Lab

   Measuring a fat bike bottom bracket width with a caliperReference Blueprint Schematic

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2. Step 2 of 6

   Insert the BBSHD Motor Unit

   Slide the motor spindle through the bottom bracket from the drive side. Because the BBSHD is significantly heavier (approx. 5.7kg) than the BBS02, support the motor body during insertion. Ensure the motor body rests flush against the drive-side bottom bracket face and does not pinch any gear shift or brake cables running under the frame.

   Schematic FIG. 2DIYPEV Technical Lab

   Supporting the heavy Bafang BBSHD motor body while sliding the axle through the frameReference Blueprint Schematic

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3. Step 3 of 6

   Install the Fixing Bracket and Locknuts

   Slide the mounting bracket plate over the axle on the non-drive side. Install the provided spacers if your bottom bracket is wider or narrower than your BBSHD spindle size. Install and tighten the large M33 inner locknut to 40 Nm using the Bafang wrench. Fasten the two M6 bolts connecting the mounting bracket to the motor housing. Thread the outer collar locknut over the axle and secure it tightly.

   Schematic FIG. 3DIYPEV Technical Lab

   Torquing down the Bafang BBSHD locknuts on the non-drive side of the frameReference Blueprint Schematic

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4. Step 4 of 6

   Install Chainring and Crank Arms

   Bolt the chainring to the motor spider housing using the five Allen chainring screws (apply blue threadlocker to prevent loosening under heavy torque). Mount the left and right crank arms onto the square taper spindle ends, making sure they point in opposite directions. Tighten the crank bolts to 40 Nm and screw the pedals back on.

   Schematic FIG. 4DIYPEV Technical Lab

   Installing the heavy-duty drive chainring onto the Bafang BBSHD motor spiderReference Blueprint Schematic

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5. Step 5 of 6

   Attach Wiring, Display, and Speed Sensor

   Mount your display unit, throttle, and brake sensors (or e-brakes) onto the handlebars. Connect the primary harness cable and route it along the down tube. Install the speed sensor on the rear chainstay and align the magnet on the spoke so that it passes within 2-5mm of the sensor indicator mark. Plug all waterproof connectors together, matching the colored dots.

   Schematic FIG. 5DIYPEV Technical Lab

   Aligning the speed sensor magnet on the rear wheel spokeReference Blueprint Schematic

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6. Step 6 of 6

   Mount the Battery and Run Power Connections

   Secure the heavy 52V battery mount to the down tube. Connect the heavy-gauge red (+) and black (-) power cables from the motor to the battery terminals using high-current XT90-S anti-spark connectors. Lock the battery pack into the mount, verify all connections are secure, and power on the system using the display controls.

   Schematic FIG. 6DIYPEV Technical Lab

   Connecting XT90-S connectors between the battery pack and the BBSHD controllerReference Blueprint Schematic

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BBSHD Spindle Length Options

The Bafang BBSHD is available in three distinct axle spindle lengths, making it compatible with almost any bicycle frame. Standard mountain and road bikes have a bottom bracket shell width of 68mm to 73mm. Fat-tire bikes, cargo bikes, and some full-suspension models have wider shells measuring 90mm to 100mm, or even 120mm. It is critical to measure your bottom bracket shell width before purchasing your kit. Purchasing a spindle that is too short makes installation impossible, while a spindle that is too long will require multiple spacing washers, pushing your cranks off-center.

For custom installations, you can use aluminum bottom bracket spacers on the non-drive side to align the mounting plate. Below is a quick-reference guide for spacing configurations based on bottom bracket shell measurements.

Thermal Management and Power Limits

The BBSHD is highly regarded for its thermal performance. However, because it pulls up to 30 amperes of current at peak output, heat can build up if you lug the motor in too high of a gear. Lugging occurs when you ride up steep hills at low motor RPM under full throttle. To prevent thermal overload, shift to a lower gear on your bike to keep the motor spinning at a high, efficient RPM (ideally above 80-90 RPM). This reduces current draw and keeps the internal controller cool.