Sanding carbon fibre

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  • Purchased a Chinese seatpost off eBay (hylix carbon road seatpost) and it currently doesn’t fit into my bike as it is c.0.5mm too big at the bottom (not the whole way up just the first 5-8cm seems to be too large). Would it be possible to sand it down to fit? First bit of carbon fibre I have owned (both frame and seatpost) and don’t want to ruin either.


  • Sanding carbon fibre is not particularly hazardous, how will you ensure that you sand it and maintain circularity? This is probably the most critical part of the process as well as maintaining an even diameter over the length.

    Know anyone with a lathe?

  • Return it and get a post that fits.

  • Too late unfortunately. Bike arrived way after post.

    @freezing77 I think I can get away with it not being perfectly round. It’s just at the bottom of the post that it’s too thick

  • The more circular the item is the more evenly is stress distributed, try to keep it as round as possible.

  • Haha ok. I am most certainly wrong then. Thanks very much for help

  • Wear some sort of mask when sanding the carbon fiber, and don’t do it inside. And cover yourself or you’ll be itchy for a day.

  • Bit late to the party but you really really want to wear PPE. Breathing in the dust isn't going to do you any good, and carbon fibre splinters are a real bitch

  • Carcinogenic carbon dust ☠️ At least wear gloves and a mask and keep it moist wiping regularily with a damp cloth . You still need to seal it afterwards.

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Sanding carbon fibre

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