Correct distance between top of threaded headset and fork steerer?
 

Planning a quill setup. Have read about 1inch threaded headsets and their stack height vs fork steerer length minus head tube length.

Q. When the headset top/lock-nut? is screwed down properly, do you ideally want the top edge of the fork to be sitting a mm or so below the headset top face?

Not sure of the specifics of the question but if the top nut/lock nut has a lip (and most do) that covers the top edge of the steerer than that steerer has to be at least short enough to clear the underside of that lip. By how much is not the issue as long there's enough thread overlap and the steerer doesn't contact that lip. This usually has a couple/three mm range.

What is meant by "headset top face"? Andy

And if the steerer is a few millimeters too long then add some spacers between the adjuster nut and the lock nut for future proofing for headsets with taller stack heights rather than cut the steerer to fit your current HS.

Unless you are dealing with a CK GripNut design which has no allowance for added spacers... Andy

I like about 20mm to an inch of spacers between locknut and cup/cone because I like fairly high bars.

And if you're asking if top of locknut should be above the top of the steerer, yes. Even if the locknut doesn't have an interior flange I'll leave a couple of threads on the locknut unused.

Someday I'll paint this spacer (cut from threadless steel 1-1/8" steerer) and top cup...



https://cimg9.ibsrv.net/gimg/bikefor...d2a3083286.jpg

Gotcha. Didn't know most will have that lip. Can picture things now re clearance required. Thanks.

As long as the stem's quill/wedge end is inserted enough to be safe (most manufactures have about a 2.5" insertion as the minimum) these added spacers are fine. The real issue is when the quill's wedge is inside the threaded portion of the steerer. The threads act as "well designed" stress risers and one can crack off the top section of the steerer if the stem is wedged there. As this area is out of sight periodically checking for cracks is rarely done. Andy

LOL, I have a Basso Tre Tubi with 2 HS caps on the steerer, which I meant to be temporary, and that was 25 years ago, and it still sits like that in the garage...

I think he means - if the stem is removed, is there a gap between the top of the steerer tube and the inside of the top nut.

you want full engagement on the threads. If the nut and upper cup are tightly locked together and there's no play, look for about a 1 mm gap inside the nut. You do not want the nut bottomed out on the steerer.

/markp

Because life is not perfect and the spacers needed to get 2mm VS 1mm of gap might not be at hand. Since both achieve the same mechanical result...Andy