I bought a 90mm compression plug so it would extend about 30mm into the bike's head-tube. But when the carbon steerer tube was cut to desired length, the compression plug could only be inserted to 75mm depth. When I looked inside the tube, there was some immovable debris down inside it, apparently from the manufacturing process. I can't clearly make out what it is. Is that a normal thing with carbon forks? The obstruction begins about 9cm above the fork's crown.

desired depth

partially inserted

freeze-frame image of debris

  • 2
    These are most likely bladder remains, totally normal. Commented Feb 6, 2021 at 16:37
  • Just smack it in there. It looks to be mostly just excess resin. If you have a suitably sized drill bit, that might be more elegant.
    – MaplePanda
    Commented Feb 6, 2021 at 17:40
  • What is the material? Epoxy? Carbon fiber?
    – Tim
    Commented Feb 6, 2021 at 18:05
  • @Tim The yellow crud is epoxy, are there appears to be a few sheets of carbon that didn’t adhere properly as well. Removing them is fine because they weren’t contributing to the strength anyways.
    – MaplePanda
    Commented Feb 6, 2021 at 20:39
  • 1
    I'd suggest using a suitably-sized round wooden dowell to push the excess down, rather than using a drill which could scratch things up.
    – Criggie
    Commented Feb 6, 2021 at 23:41


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