How to Remove a Bicycle Bottom Bracket

1. Step 1 of 5

   Remove Crank Bolts

   Remove the dust cap on the crank arm using a flathead screwdriver or coin if present. Use an 8mm Allen key or a 14mm socket wrench to loosen and remove the crank retaining bolt inside the crank center. Repeat this step for both the left (non-drive) and right (drive) crank arms.

   Schematic FIG. 1DIYPEV Technical Lab

   Using an 8mm hex key to loosen the crank arm retention boltReference Blueprint Schematic

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2. Step 2 of 5

   Thread and Actuate Crank Puller

   Unthread the inner plunger of the crank puller tool so it does not protrude. Carefully hand-thread the outer collar of the crank puller into the threads of the crank arm until it is fully bottomed out (failing to seat it fully will strip the crank threads). Once secured, turn the inner plunger clockwise using a wrench. This presses against the spindle, pushing the crank arm off the tapered axle. Remove both cranks.

   Schematic FIG. 2DIYPEV Technical Lab

   Threading the crank puller tool into the aluminum crank arm threadReference Blueprint Schematic

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3. Step 3 of 5

   Remove Non-Drive Side (Left) Cup First

   Insert the splined bottom bracket tool into the left-side cup. Ensure the splines are fully engaged. Using a large wrench, turn the tool counter-clockwise (standard right-hand thread) to loosen. Unthread the cup completely and remove it from the frame. This plastic or aluminum cup acts as a support sleeve.

   Schematic FIG. 3DIYPEV Technical Lab

   Unscrewing the non-drive side bottom bracket cup counter-clockwiseReference Blueprint Schematic

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4. Step 4 of 5

   Extract Drive-Side (Right) Cup

   Insert the splined tool into the right-side cup. On standard English BSA threaded frames, the drive side is left-hand threaded (reverse thread). To loosen, you must turn the tool CLOCKWISE. Apply firm, steady pressure. Once the initial friction breaks, spin the cartridge cup clockwise until the entire bottom bracket unit slides out of the shell.

   Schematic FIG. 4DIYPEV Technical Lab

   Turning the drive-side bottom bracket cup clockwise to loosen and extract the cartridgeReference Blueprint Schematic

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5. Step 5 of 5

   Clean and Chase Frame Threads

   Spray the inside of the empty bottom bracket shell with degreaser. Use an old toothbrush or brass wire brush to clean dirt, rust, and threadlocker residue from the internal frame threads. Wipe it clean with a rag and inspect the shell for internal welds or cables that could interfere with your e-bike motor spindle.

   Schematic FIG. 5DIYPEV Technical Lab

   Brushing internal bottom bracket shell threads to clear dirt and rustReference Blueprint Schematic

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Identifying Bottom Bracket Standards

Before purchasing your mid-drive motor conversion kit, you must identify your bottom bracket standard. Threaded bottom brackets are the simplest to convert. Press-fit systems (like BB30, PF30, BB86, BB92) do not have threads; instead, the bearings are pressed directly into a smooth frame bore. While mid-drive kits can be installed on press-fit frames, you will need specialized adapter sleeves that convert the smooth bore into a standard BSA threaded interface.

Refer to the table below to cross-reference your frame type, dimensions, and the required actions to prepare for a mid-drive installation.

Unlocking Seized Steel Cups in Aluminum Frames

Aluminum frames paired with steel bottom bracket cups are prone to galvanic corrosion, which essentially welds the threads together over time. If the cup refuses to budge under high force, apply a high-quality penetrating oil (like PB Blaster or Kroil) around the threads from both the inside and outside of the shell. Let it sit for at least 12-24 hours to soak. If it remains stuck, apply localized heat to the steel cup with a heat gun to expand the metal slightly, then attempt to loosen using the tool-securing washer trick.