Odd headset - looking for a replacement
 

I have a trekking frame from the early 90s (my guess) from a German manufacturer called Mars.

I don't know what happened to this bike, I suppose someone in the marketing department encouraged the engineers to be creative and think outside the box. So to stand out in the crowd they thought well of equipping the bike with a headset that is a hybrid between 1 1/8" and 1". The headtube races outer diameter is 1 1/8, but the adjustable race and locknut are made to accommodate a 1" threaded fork.

I couldn't find any info on this standard, let alone finding a replacement - which I need. The adjustable race has no engagement for a key, it can only be tightened by hand. This makes it nearly impossible for me to tighten the whole assembly properly. I am using this bike on pretty rugged roads and the headset unscrews constantly, which is starting to get on my nerves. I would like to buy a replacement but as said I don't even know who sells such headset, if anyone, or how are they called.

If necessary I can post some photos tomorrow.

Is the fork 1" (25.4mm) outer diameter (which is the 1 1/8" standard, or 7/8" (22.2mm) which is the 1" standard?

The standard 1 1/8" threaded headset works with a fork that has a steerer tube 1" outer diameter. "one inch" fork have a steerer tube 7/8" outer diameter.

EDIT: I am sorry, the information above that I provided is not correct; @Kontact is correct.

Ah, no. 1" forks are 1" on the outside, 7/8" on the inside, which is where the 22.2mm quill goes.

Igor, do you have to replace the headset rather than the bearings?

You might try Cane Creek's headset finder search tool.

Does your headset have an adjustable cup that have knurling
 

https://cimg5.ibsrv.net/gimg/bikefor...6a309295db.jpg
Do you have a headset with the knurled adjustable cup that does not have flats or notches for a tool to engage?

https://cimg3.ibsrv.net/gimg/bikefor...301e6b91cc.jpg
https://cimg2.ibsrv.net/gimg/bikefor...35ebc392d8.jpg
I find that the best way to adjust that kind of headset is to use a large channel lock plier to grip the knurling and then just a notched headset lock ring and a lock ring tool to set the bearing preload. Then afterwards is when I put the top locknut in just as a place holder and to help hold the adjustment.

Also Igor, I work in a bike co-op, I see quite a bit of bikes that have non-standard components. The sizing that you are describing is something that I have encountered quite a few times. Headset cups that are in between the 1" and 1 1/8" standards, but it uses a 1" threaded fork.

One of the ways that I found which made those headset function better is to use 3/16" ball bearings in the top, provided your specific headset has the room for it. Using 5/32" ball bearings (loose or caged) often time meant the adjustable cup and the top cup were bottoming out against each other and touching, so that you never can get the headset nicely adjusted.

Yes, this is precisely the genre of headset that I have. As you correctly pointed out the balls are 5/32.

I never saw those notches lock rings, but I totally understood your procedure. Will try to find them and next time I put the bike on the workstand follow your advice.

Hi Igor,

If you PM your address, I will send you a couple of the 1" threaded headset lock rings. I have a few kicking around. Just keep in mind that you would need to remove any equivalent thickness washers.

Also, do not put the top lock nut in place, even loosely before trying to adjust the headset bearing preload. Often times the lock rings are not that thick and the lock ring tools will hit the bottom of the top lock nut, not allowing you to set the preload of the adjustable cup. What I do is set the preload of the headset bearings with the knurled adjustable cup and the lock ring, then assemble anything else on top.

Cheers,
Scuba