I am in the process of building a bike with a new frame and fork. The groupset will be from a donor bike. When it comes to fitting the bike and cutting the steerer I would like to do some trial rides to check the fit prior to cutting the steerer.Can I leave the steerer long and install spacers above and below the stem until I get the fit correct? Could I leave a spacer on the top so potential resale would be more likely?
Yes. I do this on most of my bikes so I can do a quick fit for a friend when needed and to broaden the appeal for resale. Just make sure to snug up the compression like normal prior to tightening the stem and you will be good.