Dale cannon wrote:
Standard aircraft engineering practice is pack bearings to 1/3 of the space with grease. I would think that this practice will suffice for bicycle bearings as well.
Too much grease may pic up dirt and grit and turn it into grinding paste that can be detrimental to bearing life.
If you clean and re grease on a regular basis you should be fine.
Hope this helps.
I doubt that many aircraft bearings are directly exposed to mud and grit. Pack in as much grease as possible: this minimizes the space that water can occupy. However, in the end you do need to clean it out as grit inevitably gets into the bearings. Personally I fit an inch of old inner tube onto the steerer before reassembling the lower headset bearing - it then covers the entire lower headset and stops the grease getting washed out (and grit entering). Other people deplore the approach as it prevents the headset logo from being seen.
Alternatively buy a Campagnolo Record headset: it has grease ports in the side and you can give it a squirt of grease from time to time: the excess pushes the dirt out of the headset.
Ride it or milk it!