The headset brinelling is most noticeable when riding without hands where the free rotation of the front wheel of minute amounts is crucial. The way I test for brinelling is by holding the top tube of a bike on my shoulder, leaning the headtube down so the headset is able to sway like a pendulum. Knock the handlebars a bit and watch the motion .. if the front wheel tends to favor slowing and ultimately stopping/snapping to the centerline, the bearing has brinelling in this most common of positions. When riding no-handed, the wheel is resistant to tracking along a line other than center and therefore for a slight adjustment or curve, one need lean far enough to snap the bearings out of this indented position, which leads to a series of over-adjustments just to remain a desired course.

I have since tightened my headset just a skosh, enough to eliminate the play there was in the position with the brinelling, and although it probably favors this position to a greater degree, I feel good about this adjustment until I am able to replace the headset, since the lack of play should eliminate further pitting and any stress transferred to the headtube. The takeaway from this bearing casualty might be to readjust a new headset soon after installation especially if one has a tendency to err on the side of too much grease. My conception of a properly adjusted bearing is like balancing a razor's edge, being impossible to maintain with a number of factors that can move the position of this edge, and if the slightest amount of play can be the seed of bearing brinelling it would seem leaning toward a bit tight (preloaded) is better than anything loose or even 'perfect' since this can change over time.