mwnahas said:
Late 2002 and 2003 and early 2004 had changed to a different bearing. I can't say if it was better or worse but also that time the was a drop in failures. Then they changed back, not sure when exactly.
The change to the French 17 ball bearing occured around the time that the drop in failures started, but that bearing wasn't the "fix".
When the "plume" FD crownwheel bearing failures on the early model year bikes first became evident BMW changed from the German made 19 ball bearing to a French made 17 ball bearing. The "new" bearing had a different part number and the price was significantly more in the BMW parts system (Approx $130 vs $85). After a while BMW went back to the German made bearing.
Anyone outside BMW know why this change was made? Probably not.
Lots of speculation on this board as to why BMW went the the French 17 ball bearing:
One idea suggested was: One of the first things noticed about failed bearings was that the retainer was broken and retainer shards tore the seal causing lube leak. The theory was that fewer balls made more room for bigger, stronger retainer. This theory is probably incorrect, the retainer really isn't beefier in the 17 ball bearing, and the retainer failure wasn't a primary cause anyway. The retainer fails secondary to stresses placed on it due to breakdown of the balls and races. My theory, pretty well substianted at this point, is that excess preload shim thickness causes ball and race degradation, which then leads to retainer failure.
Another theory was that BMW suspected a batch of defective bearings and went to a different supplier.
Another theory was that with all the failing bearings, supply from the German bearing manufacturer couldn't keep up and BMW went to a different source.
No one really knows, take your pick of the above theories, or formulate your own.
We don't know that BMW ever actually assembled a FD with the 17 ball French bearing at the factory. Lots of people assumed that they did because that bearing was in the BMW parts supply system; I've never seen or hear of a BMW factory assembled FD with the French 17 ball bearing.
BMW did figure out that having dealerships just replace a failed bearing with another one didn't work for long. After a point in time, folks who experienced a FD failure learned that the dealership wouldn't fix it; the failed drive was shipped back to Germany and a few FD was installed.
There are many fewer 17 ball bearings in FDs out there and I don't have a sense of the failure rate, probably no one does. I rebuilt a few FDs with the 17 ball bearing, and I've seen at least one failed 17 ball bearing.
If I am correct in believing that excess bearing preload shim thickness is the primary cause of most crownwheel bearing failures, and failed drives were rebuild with a 17 ball bearing without checking for proper preload, the 17 ball bearing will perform no better than the 19 ball bearing.
I suspect that BMW switched back to the German bearing as soon as they could. I imagine the folks at BMW swallowed hard when they first subsititued a French bearing for their German one. :histerica
17 ball French bearings are probably still available in the supply departments of dealerships with slow turnover. I once decided to order a bearing from a dealership other than my usual supplier, and they wanted to sell me the "new and improved" bearing for $130, this was years after BMW had switched back to the German 19 ball bearing.