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Head tube concentricity problem
I recently bought a new gravel bike and when I got it home I noticed that the gears were not indexing properly so I made some adjustments. When riding down the street to check it out I also noticed that the headset was loose, so I tensioned it and all was well. Not wanting to ride a new bike in grotty winter conditions I put the bike in my garage. A couple of weeks later I noticed that the bearing top cap was not concentric to the head tube. Despite dismantling the headset and reassembling it I cannot get the top cap to sit concentric to the head tube. Interestingly the compression ring is made from green plastic and not alloy as I have seen on other headsets. The head tube and top cap are both 46mm in diameter and should be concentric, but the top cap is off centre by just under 0.5mm. This exposes a crescent of the machined top face of the head tube on one side, and leaves the top cap over hanging at the other. The steering turns without any tight spots but it just looks wrong. Not being concentric I think that the seal on the bottom of the top cap cannot be fully effective and will in time cause a problem. Do I need to be concerned about this? Is there anything I can do to overcome the problem?
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10 comments
Any chance you can show a photo of it?
Take a look at the attached photo.
Wow, that does look odd. I've only installed a couple of headsets, but I'm really puzzled how that can happen unless the head tube itself is not concentric.
Is that an aluminium alloy frame?
Yes it is aluminium alloy.
Any chance it has some sort of purposefully non-concentric headset adapter? Like these ones, for instance.
https://www.wolftoothcomponents.com/pages/geoshift-angle-headset
https://www.workscomponents.co.uk/20-degree-ec44-zs56-angle-headset---to...
Hello Andy
Thanks for your reply. No it's a regular FSA integrated headset.
Did you buy the bike from a shop? Because if you did, I would suggest it shouldn't have left the shop in such a state. The bearings will sit wherever the bearing seats have been machined, so it sounds like they could have been machined off centre. It probably doesn't affect the safety of the bike unless theres a manufacturing defect which results in the frame being weaker than it would have been. There's a chance it wouldn't roll straight if you rode no handed but with hands on the bars you'll probably naturally compensate for any slight off centre steering.
Have you checked that the bearing is properly seated in the frame and isn't somehow incorrectly seated and thereby pushing the headtube at an angle and making the top cap not sit centrally?
But all of this really should be for the shop to sort. If it's correctly assembled then sounds to me like a quality control issue with the frame and I would be asking the shop to sort a new frame.
Hello Tomo
Thanks for your reply. Yes I bought it new from a shop. No I have not checked that the bearing is not incorrectly seated but have already taken it back to the shop where I bought it. They couldn't find anything wrong with the set up and concluded that the problem is down to the head tube and said that it is prefectly safe and rideable so is unlikely to be a warranty issue. I will check the bearing seats in the frame as you suggest.
What brand of frame/bike is it?
If it's been assessed as safe then that's the main thing but I'd be a bit dischuffed at quality of manufacture.
I would hazard a guess the bike shop don't want the hassle of having to deal with a warranty issue. They may be right in it not being a warranty issue but sounds a little second rate - so name and shame ;-). I would at least be asking the shop to enquire with the manufacturer - send them photos etc. If the shop won't deal with it, I would contact the manufacturer direct and send them photos yourself. I've had better resolution of warranty issues before now by testing the water with the manufacturer direct than going through the shop. They might refer you back to the shop but it might be a "get the shop to return it to us, it shouldn't look like that..."
I agree with you and feel dischuffed at the quality of manufacture and in particuar the quality control. The daft thing is whenever I ride the bike and look down I see the fact that there is a problem. The head tube and top cap are the same diameter so are intended to run concentrically. Apart from anything else this means that water and dirt will run off having no ledge to land on. I don't like the look of the plastic compression ring for the top bearing and wonder if that may be causing the problem. Every other such headset I have seen has had an alloy ring. Given that the ring is under load all the time I think that alloy must surely be better. Remember that an intergrated headset needs more tension than one with pressed in cups in order to hold the bearing in place and stop the whole thing turning. I am sure that the shop will have tensioned the headset (likely in a work stand) but me riding it down the road may have caused a slight deformation of the plastic ring. Does that sound feasible? Being an OEM headset the manufacturer probably cuts cost by supplying plastic rather than alloy rings safe in the knowledge that the bike manufacturer will field any problems.
I did check and could not see that the bearings were seated incorrectly. I cleaned out the head tube and a few bits of swarf from when it was machined came out. On reassembly I could not see any difference the way it went together or looked. Inspection of the bottom end of the head tube revealed a lack of concentricity there as well.