Aheadset adjustment question

[Crackle]

The piccie below is my DiaTech aheadset on my 10 year old mtn bike. It's 1 1/8, though until recently I thought it was 1" but that's an aside.

I fitted a new riser stem to it and in the course of doing it was a bit surprised. I've never taken the headset apart, had it done at a service a few years ago but 1st time for me.

So. The grey rubber cover you see is a bung. There's no hollow bolt or star nut for adjustment underneath. When you take the stem off, the forks drop down. It does have a collar below the stem which is tapered, top narrower, bottom wider and that fits onto a tapered spacer to match.

To put it back together I had to tap the stem down and force the collar onto the spacer. I then notched up collar and stem and checked it all. It seems OK, not too tight and no slack.

So my question is, as I need to take it apart again for a clean and grease, what's the technique, in particular what do I do with that collar?

 

[fossyant]

Looks like it's a cheaper sort of headset. You'll need to keep the collar - for more accurate adjustment, maybe get a Hope Head Doctor (instead of a star nut)- it's an adjustable bung and you can pre-load the bearing, then tighten up the collar and stem.

 

[Crackle]

Thanks Fossy, I hadn't heard of that. May well get one as the bung split some when I took it out. Headset is still smooth and the bearings looked in good fettle so I don't want to replace it just yet.

 

[Landslide]

It does have a collar below the stem which is tapered, top narrower, bottom wider and that fits onto a tapered spacer to match.

To put it back together I had to tap the stem down and force the collar onto the spacer. I then notched up collar and stem and checked it all. It seems OK, not too tight and no slack.

Notching up the collar is what applies the pre-load to the bearings.
When re-assembling, make sure that the collar bolt is loose. Tap the stem down, align it with the wheel and tighten it up. Any play in the headset can then be taken up by tightening up the collar.

 

[Crackle]

Thanks Landslide, that's what I was thinking. When I took it apart the collar was loose, which probably is why it dropped. By the time I'd guessed it's possible function I seemed to have fluked it back together. I think I'll take it apart and re-do it, a) to grease it and to satisfy myself it's right.