Originally Posted by
habilis
Could this have been due to "indexed" head tube bearings? I overhauled a head tube recently because the steering felt slightly notchy. Examining the races, I saw evenly spaced shiny spots. After cleaning and re-greasing, and replacing the ball bearings, everything seems fine. (I showed the races to an LBS mechanic who also thought they were salvageable.)
I think one of the common places for the forks to bend is the steer tube which would otherwise be hidden in the middle of the head tube. Unfortunately, I don't have the bike I remember that problem with. But, a bent steer tube could well affect the headset adjustment.
The lower headset crown race on my Colnago is getting pretty badly washboarded, but it doesn't seem to affect the steering. I should probably either polish the crown race, or replace it. Maybe for the next rebuild.