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After a crash, I noticed my bottom headset cup was no longer sitting flush with the frame (see the right side of the image below). If I grab the headset cup I can rock it back and forth slightly. No cracks I can find at all.

Is it possible to repair this and get the headset cup to sit flush/tight again or is the frame ruined?

enter image description here

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  • Do you notice any impingement or restriction when rotating the bars? I wonder if it was like that before and no big deal. Otherwise, put a 2x4 on it and hit it with a hammer.
    – jqning
    Commented Apr 17, 2020 at 14:00
  • No it was not like that before the crash. If I put the fork and bars back on I can get it to rotate smoothly with no apparent play, but if I push the bike against a wall hard enough I can feel a slight clicking. I assume this is the headset cup rocking back and forth in the frame.
    – John
    Commented Apr 17, 2020 at 18:51

2 Answers 2

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The frame tube around the cup may have been 'ovalized'. The fork can exert considerable leverage on the bottom of the head tube.

The bearing cup needs to be pulled out and the frome inspected. Specifically you need to check if the tube recess for the cup is still round. This can be done with a good set of digital calipers by taking inside diameter measurements at right angles to each other.

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  • I pulled out the cup. The frame is definitely "ovalized" as you said. The deformation is visible just by looking at it. It is nearly 1mm wider front to back than side to side, but the deformation is less and less as you go further up into the headtube. Is the frame salvageable or should I trash it?
    – John
    Commented Apr 17, 2020 at 18:42
  • @john hard to say. I don't have any experience with deformed head tubes. The answer is also is going to depend on how much the frame is worth and if it has any other damage. You can try searching this site for info about potentially fixing a head tube or ask a new question of you don't find anything
    – Argenti Apparatus
    Commented Apr 17, 2020 at 23:43
  • Thanks. I posted a new question now that I have a better idea of the issue with pictures of the cup removed : bicycles.stackexchange.com/questions/67405/…
    – John
    Commented Apr 18, 2020 at 21:13
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You will need to remove the cup and inspect both the frame and the cup. The cup is made out of a thinner material than the headtube so it is most likely that the cup was distorted. You will also want to do a thorough inspection of the fork and the frame. Scratches in the headtube are fine as long as the tube is not distorted or cracked and the new cup fits tight you should be fine.

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  • I pulled the cup out. The cup appears perfectly fine and round. The deformation is definitely on the headtube at the back where that gap is in the photo. I assume this means the frame is ruined?
    – John
    Commented Apr 17, 2020 at 18:45
  • Default answer is that the frame is ruined. It's compromised and cannot be fixed. No real mechanic will tell you otherwise, because there is no official repair possible. If you have to save the frame, you can make sure the bearing cup is good, or preferably get a new bearing cup/headset, then epoxy it in with JB Weld or loctite 680. Assemble the headset while the glue dries to ensure alignment. It should be fine then, but standard disclaimer applies. No bike shop will do this for you because of liability and because they would rather sell you a new frame.
    – BetterSense
    Commented Apr 20, 2020 at 2:04

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