A customer dropped off the rear wheel of a Bora One 35 with us.
A spoke broke and flew off during a ride.
↑The spoke is bent—what happens here is the spoke head breaks from the impact, and the spoke springs outward toward the rim's circumference. Then it gets caught on the rim's spoke hole, resulting in this deformation.
A standard spoke head fracture. While I say "standard," this type of spoke failure is pretty rare—maybe one in a few dozen spoke replacements. Most spoke issues come from deformation due to external causes like crashes or accidents rather than fractures. And when fractures do occur, the overwhelming majority break where the threads begin.
Separate from the spoke replacement, I noticed a faint grinding sensation when I spun the hub axle by hand. When I held the sprocket and tilted the free body upward in an off-center direction while rotating the axle, there was a distinct grinding noise, confirming the bearing was damaged.
So I replaced it. Only the outer bearing was damaged.
All fixed.
↑The replacement spoke
↑This is what the spoke head fracture surface looks like
↑This is what the deformation looks like
Years ago, I had a spoke break on my own Nomulab Wheel No. 4 while going downhill on the Osaka side of the Hanna Expressway. I thought I couldn't find the broken spoke at first, but it turned out that most of it had been dragged inside the rim.
A spoke broke and flew off during a ride.
↑The spoke is bent—what happens here is the spoke head breaks from the impact, and the spoke springs outward toward the rim's circumference. Then it gets caught on the rim's spoke hole, resulting in this deformation.
A standard spoke head fracture. While I say "standard," this type of spoke failure is pretty rare—maybe one in a few dozen spoke replacements. Most spoke issues come from deformation due to external causes like crashes or accidents rather than fractures. And when fractures do occur, the overwhelming majority break where the threads begin.
Separate from the spoke replacement, I noticed a faint grinding sensation when I spun the hub axle by hand. When I held the sprocket and tilted the free body upward in an off-center direction while rotating the axle, there was a distinct grinding noise, confirming the bearing was damaged.
So I replaced it. Only the outer bearing was damaged.
All fixed.
↑The replacement spoke
↑This is what the spoke head fracture surface looks like
↑This is what the deformation looks like
Years ago, I had a spoke break on my own Nomulab Wheel No. 4 while going downhill on the Osaka side of the Hanna Expressway. I thought I couldn't find the broken spoke at first, but it turned out that most of it had been dragged inside the rim.