Originally Posted by
cyccommute
Stem and spacers may have to be installed with the fork and headset. For threadless, you can't keep the fork in place without them.
What I meant here was to install the bottom part of the headset first, then build the bike up and ride it around a bit. There will be a bit of movement in the fork but it's a good way of making sure you can get the handlebars at the right height. You can add remove spacers at this point. Then when you are happy with the height, you can get the fork cut and install the star nut and the rest of the headset.