Originally Posted by
billyymc
If it would work with your fork, I'd spring for a threadless headset, and forget the adapter. I did it on an older Trek MTB I have - worked nicely. I had to get a new fork at the time though.
I'm not sure how you would ever not need a new fork - a steerer tube cut for threaded is too short for threadless, since it must extend above the headtube. There would be nothing for the stem to clamp onto.