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31 Comments

  1. ScallywagSingletrak on

    I dont like carbon frames especially used you never know how its been treated, relative innocuous bumps and knocks transporting them can mean disaster, never mind a crash. Hope you can find a skilled craftsman.

  2. Looks cracked, I’d suspect that there was a too small seatpost used at some point.

  3. Looks like structure damage.

    Pull the post out and see what the inside looks like.

  4. Thanks for all the replies guys. The inside is not yet compromised, however there is no paint underneath the seat post collar at all. It’s hard for me to tell if the bike was sold this way or from previous owner. Have sent him a message to find out.

  5. AmosRatchetNot on

    Looks like carbon to me. Probably fine to ride on so long as post insertion is kept proper.

  6. _maple_panda on

    Rest assured that even if it is carbon damage, it’s not a huge safety issue. Worst case scenario is that the top bit of your seat tube rips off. It’s not like this will lead to your head tube snapping off or something. I don’t think this would be too expensive to repair either (now, not after there’s a catastrophic failure).

    Do keep in mind that if this was the result of neglect (eg. wrong seat post used), the rest of the bike might have hidden issues too.

  7. The worldwidecyclery guy cut his frame on a carbon yeti a few years ago. Didn’t look that hard honestly if you decide to just cut that section out. It’s on YouTube or atleast it was. But I honestly wouldn’t be that worried about it if the seatpost is installed deep enough now.

  8. You have to scratch off the paint to find out. Send them the photos and if it’s just paint ask for touch up paint from them.

  9. That’s carbon. Most likely at one point there was a too small seat post in it and someone tightened the clamp ring around it causing the carbon to crack.

  10. bags-on-skis on

    Don’t come on Reddit asking for help if you are only looking for one specific answer. That’s cracked carbon without a doubt. Sorry but it will just keep breaking further unless it’s repaired. It costs money. Period.

  11. Is the seatpost the correct diameter for the frame spec? If the post is too small, then the clamp needs to be tightened beyond the spec to get the carbon to frame “grab” the seatpost. This will work for a bit, but besides jacking up the frame, it loads up a huge amount of force on that very tiny spot of the seat post and next thing you know, snap, crackle and pop.

  12. NUCLEAR_BLUMPKIN on

    Get a torque wrench if you own carbon. That’s very likely from the bolt being over-torqued.

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