Originally Posted by
rms13
This is my first full carbon fork so I'm used to round tubes and star nuts. Apparently this Easton EC90 steerer has two flat edges on it and round the rest of the way. It has an SI integration compression bolt. The top of the steerer looks slightly uneven. Not sure if that matters. I have 30mm of spacers above the stem that I will want to cut off so I'm not too worried about the top of the steerer
I still suspect that your issue is because of barrel shaped distortion of the steerer. Essentially the stem is clamping on the sides of the barrel and free to rock (slightly). after adjusting and tightening, try removing the expander, or a least loosening it materially, and see if it's possible to take some more on the clamp screws. If so, that was the issue, and relaxing the expander should have solved it.
BTW- not all creaking is stem/steerer. Sometimes the steerer itself flexes under load causing some movement of the bearings, so don't get tunnel vision. If nothing you do solves the problem, open your mind to other possibilities.