Originally Posted by
bent-not-broken
Is the headset free and properly adjusted? I have had several older bikes which pulled to one side due to binding in the headset.
One of my most recent changes was to lower my stem, which did involve re-tightening the headset stem cap, maybe I cranked it down too far. Another thing I have noticed recently (but not thought of it much), when I walk my bike to/from my cube at work, I sense steering squirreliness, but I put that down to rubber tires on industrial carpet. Only noticed it recently however.
I bet this will be the winning suggestion. I will loosen the stem and put it back less tight, see if the carpet-squirm and the leaning goes away.