So I've had a rattling noise in my threadless headset whenever I run over uneven surfaces in the road. Even small minor things that I ride over, my headset will rattle. I've taken it apart many times, regreased everything and put it back in, but the problem still continues. First, I thought the problem was that it may have been loose, but I've tried tightening my headset. Then, I thought it may have been my wheel that was causing the problem, but when I switched front wheels this problem still continued. My only guess is that the compression ring I put in after the upper cartridge bearing is the thing that is making the noise. To me it's the only thing that could be possibly moving around. I don't really know what to do about that though. I don't know if this means anything but I also have a carbon fork.
So my question, are there any other possible explanations for this? What can I do to make it stop!?