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I've been over-tightening presta valve cores for years and only realized it when one snapped in a customer's tube yesterday.
The tip-off was the tiny, clean break right at the base of the valve stem, which happened while I was just snugging it up with my fingers, not a tool.
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sarah_brown4d ago
That clean break pattern means the brass was already fatigued from previous over-tightening.
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ross.kelly3d ago
Actually looks more like a casting flaw.
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