Originally Posted by
Road Fan
Conventional wisdom is to tighten ONLY as much as will eliminate play, but I think with a perfect installation it can be tighter. If it's tighter, it would take more ride load (forces of weight combined with impact loads) to cause the balls/races to separate due to head tube flexing.
I disagree. See
http://www.sheldonbrown.com/brandt/i...-steering.html
for a discussion of the fretting oscillations that can result in an indexed headset. Having it tighter than necessary would displace lubricant from the bearing surfaces and also inhibit free motion of the balls within the bearing while going straight. That increases the chance of such fretting damage. A little tighter is fine for a bearing that is normally rotating, such as in a hub or pedal, but not for the headset that is subject to vibration while stationary.