Seat clamp bolt too tight to undo

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  • Got a carbon bike with a carbon seat post and it has one of those wedge seat post clamps integrated into the frame so like the synapse and giant defy. 4mm hex bolt. Bolt isn't rounded off just yet. However, I cannot get This bolt to turn to get the seat post out. The bolt is so tight that my Allan key feels like its going to snap. Any suggestions? I've tried using gt 85 and some plus gas, but I don't think there is enough gap to penetrate this bolt. Suggestions welcomed before I end up stripping the bolt head.



  • try tightening it a tiny bit, that will break the corrosion bond (if there is one) and allow you to undo it without rounding the head off.

  • Thanks mate mets give that a go.

  • No worries. Another thing you can do, as I’m assuming it’s stuck from corrosion, is to put a small bolt or screwdriver in to the hole of the Allen bolt and give it a few whacks with a hammer to shock it. Obviously don’t hit it in a way that will do damage but giving it a sharp tap may help break any bond and allow a penetrating fluid in to help you undo it

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Seat clamp bolt too tight to undo

Posted by Avatar for Yusuf987 @Yusuf987