Originally Posted by
jonwvara
I had just read the same info on the Park site and came to the same conclusion that you did. I'm going to ask some experienced frame builders what they think of the idea, but at this point it seems likely to me that there's no difference between the tubing used for either type of steerer.
It's likely, but I wouldn't assume it is.
Obviously the OD of all 1⅛" threadless steerers is the same, because the ID doesn't matter to a threadless system. But just as obviously, the ID matters when you intend to use a quill stem. Since it's possible to make a 1⅛" threadless steerer thicker or thinner than a threaded one, I'd make sure the ID is within spec. IOW, measure it. A too-thin wall will make for a pretty risky threading operation. A too-thick wall will make getting that stem in pretty difficult.
FWIW, I've seen 1" threadless steerer tubes that have a thicker wall that would preclude using a quill stem unless it was French OD of 22.0mm. Even then the fit was tight.