I was working on my Felt F55 (all stock) yesterday and noticed my headset seemed a little loose. I put a new stem on (was planning on doing that) and retightened everything at 5nm with a torque wrench, yet its still not tight down there. I can definitely move it around but don't hear anything going on. I didn't spent the most time on it, I put it back together thinking that retightening everything would fix the problem but it didn't. Definitely not taking it out on a ride until I get it fixed, anyone have any idea what is going on there?

The new stem may be a bit less tall than the old one so you may need to add a spacer to get the compression bolt/top cap to properly compress the headset. Remember that the stem/spacers must overlap the top part of the steerer tube for the top cap to properly compress the head set, i.e. the steering tube must not be sticking up from the top of the column of spacers/stem. Tighten the top cap so that the fork rotates smoothly and there is no play in the headset when you rock the bike with the front brake applied. When you're happy with the preload on the bearings and the bars are lined up straight, tighten up the stem bolts to finish the job.

It wasn't so much an issue with the new stem, it was loose with the old one on there and I thought retightening after putting the new on one would do the trick. But I think you hit on what I did wrong. I realized I tightened the stem before I did the top cap, so it didn't have a chance to compress it enough. Too bad I can't do it right now, but I will try that in the morning and hopefully it should do the trick.

https://www.parktool.com/blog/repair-...ice#adjustment

Like bobones said, for threadless headset, set the bearing preload with the top cap screw first while the stem bolts are loose. When happy with the preload, then tighten the stem.