Other considerations to threaded headsets besides fork diameter?
 

I popped into my local shop inquiring about buying a threaded headset for a used bike frame I'm upgrading. The fork is threaded and has a 1 1/8 diameter. The guy told me it would be better to bring the frame and fork in. He gave me the impression there was more to the purchase than simply fork diameter and threaded/threadless compatibility. I thought headsets were a cut and dry topic with only two factors to consider: threaded/threadless, and fork/steerer diameter. When the mechanic/store owner was talking to his colleague/son about my frame (he removed my headset cups last week and recalls the frame) he mentioned integrated headsets. There are some language barriers present, so he wasn't able to fully articulate everything, but he basically told me there was more to this than what I thought.

The bike is a mid 90s Giant mountain bike. I thought integrated headsets were strictly a threadless topic. I almost bought a frame that required one, which is something I looked into afterwards.

The guy seems pretty honest. What am I missing? All threaded headsets I find online appear to differ only in regards to steerer/fork diameter, and nothing else.

You need to match stack height because your head tube length and steerer length are now fixed.

You're probably right but, if I were running the shop and somebody came in to ask me the same question, I'd want to see the frame and fork too.

we ask to see the frame to confirm measurements. are you going to keep the headset if we order the "wrong" one? gets even trickier if they want a taperd for and have a zero stack headtube. sometimes the phone conversation is not entirely clear. when we have the parts we know what we are looking at and what you want. i am talking more along the line of odd ball stuff. most shops should stock a basic 1 1/8 threaded headset. cost maybe 20 bucks

+1, Bring in frame and Fork.. to the LBS..

With a 1" steerer, you have two or three possible crown race IDs, IIRC... not an issue with 1[SUP]1/8[/SUP]" AFAIK.

1[SUP]1/8[/SUP]" steerers can go inside a variety of head tubes, but that's just the threadless ones; if your fork belongs to your frame it should be a traditional head tube with normal cups.

Although, I can't see why it wouldn't be possible to mount a threaded steerer in a zero-stack headtube; you'd just need a lockring and locknut on top in place of the stem. The split cone would likely be pretty stubborn to remove after it was jammed onto the threads, though.