How to undo threaded headstock nut?
 

I have a bike that needs new headstock bearings. However the nut has no flats for a spanner. How do I undo it? (Apparently I can't post a picture yet)

To post a picture you can make 4+5 more posts (10 total) in the various currently active threads all over the forums. It will allow you to get to know the forums and get involved in this great community and then once you get to those 10 total posts you will be able to post pictures and links.

You could also give us info on the bike as well and maybe someone can figure it out as posting the most info you can is always helpful though yes pictures are worth 1000 words!

You can upload pictures into an "Album" associated with your user name even before you get ten posts. Then, one of us can link to the pictures in that album to display them here.

Fresh Fish!...

Usually, the top lock nut has flats for a spanner. The bearing piece itself (cup or cone) might not have flats or notches. If it has a knurled edge, you can use an appropriately sized channel-lock pliers or vicegrip.

I looked at OP's headset in their gallery easy enough but am not familiar with that one.

I think this is the image you tried to upload.

https://cimg0.ibsrv.net/gimg/bikefor...4c42154d12.jpg

https://www.bikeforums.net/g/picture/35461960

It looks like this is on a threaded steerer tube. Have you tried to remove the black ring near the bottom of it to see if there is a set screw covered by it? If there is a set screw, then loosen or remove the set screw and undo by hand. I've never seen this one either. But I had one that did have a set screw and removed as I described.

Doing a search for the name unterhausen provided, I found a match on eBay that has all the peices laid out.

https://www.ebay.co.uk/itm/305117646890

Since it has the big nut, this might just be a cover on the outside that you just pry off. But, if it doesn't, then any prying might ruin it.

Still check underneath that black ring if it seems like it will stretch and pull out when you grab if with a pick or something.

I saw that listing. I would probably try prying gently between the cap and the steerer.
They definitely have some models for unthreaded steerers, and they may make different caps for that.

+1. Just guessing but that may just be a fancy spacer that pulls off to reveal the nut. Might take a good tugging.

This listing shows a drawing. It looks very much like the conical cap is a press fit. A love tap with hammer and screwdriver from below will either make it budge, or it won't.

https://www.merrysales.com/shop/tang...attr=3208,1086

Wow, I'm so grateful for your expertise and efforts to help, thanks very much 😊 I have removed the bearings, the bottom one of which was absolutely fubar! New bearings ordered. Thanks again 👏👏👏

So was it just a cap that pulled off?

The ring is just a trim cap. pry it off with a screwdriver and find the lock nut underneath.

Hi all, thanks again for your previous help. I have just received the bearings reassembled the headstock, but the lil' cap doesn't seem to go down as far as it did in the original picture. Do you know what the issue might be? (I'll try and post a picture, but I don't think I'm allowed to yet...)

I have put photos in my album but can't link to them...

https://cimg1.ibsrv.net/gimg/bikefor...693efa24d7.jpg
https://cimg6.ibsrv.net/gimg/bikefor...d5c4a66371.jpg

Photo assist
Did you have sealed bearing or a caged bearing? bearing might not be installed correctly to lay in the race properly thus taking up room.
Note the space between the adjusting nut/race of the top picture which is not showing in the other picture.
Pictures are not showing the bottom of the head tube but the bottom bearing may also contribute if not installed correctly also.

Thanks JoeTBM for the response.
You have a good point re. bearings not seated properly, but they feel very good. Smooth running and no play.
I tried the aluminium disc on top of the nut (pic in album, thanks). I have a vague recollection of that setup, but the bearing really does not seat properly. I think that alu disc is the main water seal for the top, but it's not going back together as easily as I hoped. (The benefits of photo documentation!)
The cross sectional diagram that was kindly posted earlier doesn't show these aesthetic outer bits in much detail.
What should one do? LBS? 😂👍

Incorrectly installed lower bearings won't affect the gap at the top, they will just reduce the available thread for the locknut (apart from the obvious crunchiness). But definitely check both sets. I managed to invert an upper clipped ball set recently, an immensely embarrassing error for someone who's been wrenching bikes for as long as I have. At least nobody knows about it.

My lips are sealed! :innocent:

Thanks Grumpus, I think I have put the bearings in correctly?! 😅 They both seem to go in this way round (sorry, picture is in album 👍)

Need to see the corresponding headset parts to be sure.

Agreed but if they are sealed bearings (OP never answered that question), some have a beveled edge (angular contact bearing) to fit the cup, the squared edge facing into the cup could cause that gap. If OP has one bearing incorrect I would also check the placement of the bottom one as well.

It's a Tange Seiki Vantage ZSELT. I found this which should make it clear:
https://cimg0.ibsrv.net/gimg/bikefor...5d7f0c126f.jpg