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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?
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.
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.
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.
JB weld is your friend here assuming it's epoxy. Would probably be better than new then.
How’s your steerer? Any signs of the ring of death?
On the angled bearing seat that looks like they've exposed a void when they've machined the bearing seat, the bearing outer shell sat on that should be static (rotationally and in terms of any other lateral movement the inner diameter of the cup should locate the bearing outer) so it shouldn't be affecting anything as it's a sub-flush surface. If you wanted you could fill it with some epoxy and just sand it back flush but I'd probably just leave it.
On the vertical walls though in the region of the void and also just right of the straight-ahead is what looks more concerning/of note to me, that does look like damage from the top bearing moving (or is allowing the bearing to move, having been there from the start) but I think it would be hard to establish which came first, the wear or the movement.
A guy I work with (composites industry) has repaired similar issues quite regularly so it's definitely doable if the seat has ovalled/worn, you can use an epoxy to repair the bearing seat and utilise a bearing outer race to 'mould' the repair to the correct size and shape. There'll be people that can do that for you, definitely.
My recent Santa Cruz Tallboy had this problem. The upper headset bearing always moved very slightly on its seat. The bearing seat was slightly oval/over-sized from new. I'd tighten everything up but movement and creaking would return within a ride or two.
Santa Cruz agreed that it was a manufacturing fault and gave me a new frame 🙂
If I didn't have the warranty, then I would have built the seat up with a small amount of epoxy and lightly sanded to give a snug fit. Or get a carbon repair expert to do it!
