Replace the Damaged Crank Arm

Since the internal taper is rounded, the crank arm has suffered permanent mechanical failure and cannot be repaired. Follow these steps to restore the drivetrain:

1. Use a dedicated crank puller tool to safely remove the damaged crank arm from the spindle.
2. Inspect the bottom bracket spindle; if the spindle itself shows signs of wear or deformation, replace the entire bottom bracket unit.
3. Obtain a new crank arm that matches your specific bottom bracket standard (JIS or ISO).
4. Ensure the spindle is clean and dry—do not apply grease to the taper—then install the new crank arm.
5. Torque the crank fixing bolt to the manufacturer's specification, typically between 35 and 40 Nm (25–30 ft-lb), to ensure a secure interference fit.

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