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While assembling a carbon bike, I found this void in its seat tube. It's about 1/2 inch X 1/4 inch in size and I'm guessing almost a third to half the depth of the tube wall.

Since it's right next to the clamp, it looks like a catastrophic failure waiting to happen. What would be your opinion about this? Would this bike be safe to ride? Is there anything that can be done to repair it?

Carbon seat tube void

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  • Can you confirm that the material all around that area is non-metallic? It looks kind of like the entire seat cluster is a cast aluminum piece. – Nathan Knutson May 27 '20 at 17:31
  • Looks definitely metallic, especially if you look at the edge at the top where the paint has flaked off. – Carel May 27 '20 at 17:38
  • I checked with a magnet, it's non metallic. My guess is the grey stuff is a resin or epoxy. It looks similar to the inside of the fork tube. You can also see the carbon weave in the layer at the bottom of the void. – Dhiraj Bokde May 27 '20 at 18:00
  • Sorry, I was wrong. Of course, aluminum is not magnetic. But I don't think the area at the top of the seat tube is aluminum. Picture shows a metal insert to provide threads for tightening screws. If the surrounding material was metal, it would have been easier to beef up the rear of the tube and use that to form the threads. – Dhiraj Bokde May 27 '20 at 18:28
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    If it was new, check with the supplier about warranty and being "unfit for purpose" – Criggie May 28 '20 at 0:34

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