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Had a customer's carbon seatpost fail on a routine service ride last Thursday. The 'just a light torque' crowd is wrong.
It was a 2021 model, not even that old. I'd just done a full strip and rebuild, including greasing the binder bolt threads with Park Tool PPL-1. Torqued it to the spec on the post, 5.5 Nm. Customer took it for a test spin around the block, heard a crack, and the post slipped. Found a hairline fracture right at the clamp area. Everyone says you just need a light touch with carbon, but I think the bigger issue is inconsistent manufacturing on the cheaper end. This was a known brand's second-tier model. How many of you have seen similar failures that weren't from overtightening?
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nancy5007mo ago
Man, that's scary. My buddy had a nearly identical thing happen with a carbon handlebar from a big brand's cheaper line. He torqued it right, maybe even under, and it still developed a tiny crack at the clamp after a few months. We both figured it was a bad layup or a void in the resin, something you just can't see. Makes you wonder how much of this is bad luck with a single part versus a whole batch problem.
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robert_anderson697mo ago
Yeah, and it's that hidden flaw that gets me. A whole batch means a recall, but a one-off just feels like Russian roulette. How many people ride on that same bad layup without knowing until it's too late? You put your trust in the torque wrench, but what good is that if the material itself is junk from the start? Makes you question if the cheaper lines are just where they dump the factory seconds.
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paigep206mo ago
A crack from just torquing it right? That's terrifying.
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