Can someone knowledgeable take a look at this photo of the headset on my 2005 Trek L300 bike and verify that it is an integrated headset? From Sheldon's page https://www.sheldonbrown.com/headsets.html my understanding is that since the cartridge bearings are inside rather than on top of the frame walls, that means it's integrated.

I was intending on replacing the threaded 1 1/8"suspension fork with a threadless carbon fork by replacing the headset and stem with threadless. But now that I see I have an integrated headset, that means I cannot replace the headset, right?

So given that threaded 1 1/8" forks are very rare, and I need a rather specialized sort of fork (cyclocross style for 700c with canti bosses), I think the likelihood of finding such a fork is essentially nil.

I have backordered a threadless Nashbar NS-CYF Carbon fork for $120, and I'd like to install that. It sounds like my best option is to bring the fork into my LBS, and have them cut threads in it. Then I leave my headset alone. Does that sound best?

Some variation on what bearings get used in different brands of integrated headset.
have to take the bearings out and measure to have any basis on the compatibility
with current parts specifications.

No, forget threading ... More sensible is complete the threadless conversion,
stem clamps around threadless steerers rather than go inside,
and tightening wedges.

and headset adjustment is only with small allen wrenches, no big open end spanners needed ..
headset can stay, if you can sort out the collar at the to of the top race.

LBS can see what you have , the 1 picture is not as good.

1. I'm not sure why you claim that you can not replace the headset.

2. Cutting threads into a steerer that was not designed for it is generally a bad idea.

3. Even if you could thread, is the ID of a 1 1/8" threaded steerer the same as the ID on a threadless one? (So your old stem would fit). I don't have a answer to this question.

Most likely the ID of the new carbon-fork is smaller than the factory fork (due to being aluminium), so the quill stem will not fit. Remove the bearings and measure the ID of the headtube. Then look at the bottom of the Park Tool headset standards page and see what non-integrated headset will fit. If not, your shop should be able to ream out the headset to accept a standard headset.

Interesting idea... you're proposing that I leave all of the original headset in place except the top nut which is threaded. Then I use a seatclamp or similar to hold the adjustment. This will look like the second photo in Sheldon's handsup page:

https://www.sheldonbrown.com/handsup.html

That might be the way to go if it works; I also like that I will be able to adjust the handlebar height without messing with spacers and headset adjustement.

The original quill is stamped 25.4mm, which according to Sheldon's page

https://www.sheldonbrown.com/gloss_st-z.html#stem

is the standard ID for 1 1/8" steerers, so I don't think I'd have a problem if I went that route unless there's something I'm missing.

I just assumed that the integrated races would not leave room for a new threadless non-integrated headset. But I'll take a look at that Park page and see if there is a threadless headset to replace my threaded one.

No it isn't standard for threadless 1 1/8" fork, steerer tube thickness varies from company to company.

Id say ream out the top collar so It will slide over the new threadless steerer..
or just get something else that will ..


sort out the collar at the top of the top race. it will sit on top, then the spacers
sit on that and the stem atop the spacers ..

though the Sheldon kludge is interesting, you have to find someone with a cutting die for 9/8'' steerers.
that would be perhaps even harder than finding the fork.

if you are going to go (sorta) threadless ... just go for the full conversion it's more practical .

a bike shop can pull parts out of stock bins and see what works

There's "integrated headsets" and there's "hidden" or "zero stack" headsets. They're not the same thing.

Integrated headsets have an angled stop that's machined into the head tube. The bearing is a drop fit onto the stop and the angled interfaces center and align the bearing as the pre-load is set. That, by the way, is the feature that Chris King objects to.

Hidden headsets have cups that are press fit into the bike's headtube. The "hidden" factor simply means that the cup is contained within an oversized head tube rather than set atop and below the head tube as it was on conventional headsets.

I suspect your bike has the second but I can't tell from the photo.

Yes, that does sound like what I have... the bearing cartridge on top cannot be easily removed even after removing the fork/steerer. It seems to be pressed in place.