My theory to early head bearing failure

[soupdragon]

To me, one possible reason for some F series bikes eating head bearings is in-accurate machining of the headstock and/or stearing stem faces. If any of these surfaces are not completely parallel to each other then the bearings will not sit squarely. This would place all the bearing load on only a couple of rollers perhaps leading to very early indentation. I'm not an engineer and would be very happy to be proved wrong if my understanding of this matter is wrong.

 

[thomo57]

I've replaced three sets of head bearings and the indentation wear marks have always been equally distributed 360 degrees around the race.


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[kyojitsu]

So just crappy quality then?