Originally Posted by jrh2020
The false brinelling appears to be limited to stationary vibration environments. Found a little more reputable site, page 12 & 13 of the pdf.
The cage damage wouldn't appear to fit very well with this theory either.
I'm out of ideas, but the installation stress fits as well.
This is a really great link! Thanks.
I think I am seeing primarily two things contributing to the failure of these bearings:
The section on Flaking Caused by Preload fits many of the failed bearings I have seen. The section on Surface Distress also applies because surface distress will occur secondary to excess preload which decreases the lubricant space between the races and the rolling surfaces.
The section on Surface Indentations also makes sense for some bearings I have seen; the one pictured in this thread may be a good example.
Damage to the cage (retainer) is secondary to damage to the races and balls IMO. Improper installation resulting in Surface Indentations and excess preload resulting in Flaking (spalling) are both probable causes of the failed crownwheel bearings we are seeing. Once the defects in the races are established, the balls encounter increasing resistance during rotation under radial load (the weight of the bike, rider, etc.) and the stress builds on the retainer until the retainer fatigues and breaks.
When caught early by the rider sensing roughness, I have seen damaged races but with the retainer intact. Others, such as the bearing pictured in this thread, had damaged races, and early retainer failure. Note that in the case of the bearing pictured in this thread the broken retainer wasn't identified until the drive was opened and the bearing viewed. The most common stage of bearing failure detection is when shards from the broken retainer tear up the nearby oil seal and the lube leaks out.
While potholes, improper lubrication, damage due to extended trailering are all possible causes, I think that the rash of crownwheel bearings seen in the early years of the K1200LT are the result of improper bearing setup and/or improper installation techniques. I think the data available now pretty well supports this theory.
Thanks to all who have contributed thoughts, suggestions, experiences, and bearings to this inquiry.