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Damage to carbon bearing seat

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[#13536458]

Cannondale Synapse 2021.  I've always had a slight issue with the headset going loose on this bike.  I'd adjust the preload, torque up the stem and ride it and after a while it would go slightly loose again (very slight, and quite hard to separate from tyre/brake pad movement). 

I'd bought a Kinesis headset bung to replace the Cannondale one as I thought a longer bung might not slip (which is what I'd guessed was happening). 

Took the fork off to check the bearings (which are running smoothly), cleaned up the bearing seat and noticed this pitted groove on the seat. Without a clamp on it the top bearing had a very slight rock.  

Anyone seen this before?  Is this a manufacturing fault that's been the cause of the headset going loose regularly or has this been caused BY the headset becoming slightly loose (it's not like I'd ever run it badly).

To me it looks like a void in the carbon that was revealed when the bearing seat was reamed (but I dont even know if thats the process with a carbon frame - is it just moulded?) which should have been rejected at QC? 

 IMG_1983.jpegIMG_1984.jpeg  

 


 
Posted : 27/07/2026 5:23 pm
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It looks rough to me, whether that's wear or a manufacturing issue I don't know, which I guess is your question.

Lifetime warranty, I think, so go for it and see what they say. 


 
Posted : 27/07/2026 6:12 pm
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If that's the lower bearing seat, the possibly something got in there to cause the fretting/abrasion. It looks repairable, but would need the bearing seat re-cut which would be a fairly specialist job. Best to see if it's covered by the Cannondale warranty to see what they say but bearing seats are probably considered 'wear' items and are excluded.


 
Posted : 27/07/2026 8:28 pm
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Posted by: dovebiker

If that's the lower bearing seat, the possibly something got in there to cause the fretting/abrasion. It looks repairable, but would need the bearing seat re-cut which would be a fairly specialist job. Best to see if it's covered by the Cannondale warranty to see what they say but bearing seats are probably considered 'wear' items and are excluded.

it’s the top. Have always thought dropping bearings directly into frames seemed a bad idea. 

 


 
Posted : 27/07/2026 9:00 pm
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JB weld is your friend here assuming it's epoxy. Would probably be better than new then.


 
Posted : 27/07/2026 11:11 pm
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How’s your steerer? Any signs of the ring of death?


 
Posted : 28/07/2026 7:55 am