OakLeaf - I've always done my own bike maintenance (unless it requires highly specialized tools) and have adjusted old style headsets before, but I have never worked on an aheadset.

Laura* - I think I got it now, the top cap establishes the pressure on the bearings (ie, the headset bearing adjustment) and the stem maintains that setting. Thanks.

Another unknown for me (having never dealt with this kinda of setup before) is whether I have to do anything to the Specialized's expander plug inside the steerer tube. I assume not, since I will only be lowering the stem a bit and the stem would still be clamping on carbon fiber steerer tube that is supported internally by the expander plug.

Jean