Thanks, i have been researching the m3post thread you mentioned and found this which gives us a better indication of the difference between the 088/089 bearings and the new 702/703 bearings. So from the measurements there is a difference between the 2 and not just the lead.
"Graphs and Conclusions
I created the graphcs as a scatter plot with a "best fit" polynomial line to follow the contour of the measurements. That's when the results really jumped out and you could visually see for the first time how these bearings have changed. Not only did the bearing clearance change between 088/089 and 702/703, but so did the eccentricity. The eccentricity didn't change by a little, it seems to have changed by a LOT! See for yourself.
"Common" Eccentricity
Conclusions and my $0.02
When I was asked to measure bearing eccentricity, I had no idea what I would find. I guess I presumed that 088/089 bearings would both follow the same guidelines and show the same eccentricity. Even when I was measuring and looking at the numbers, I was making that presumption and didn't notice any differences. It wasn't until I looked at the graph that it became very obvious that something radical had changed.
The bearing eccentricity changed from 0.00085 inch on the 088/089 bearings to 0.00200 inch on the 702/703 bearings. That's a 2.5 times increase in eccentricity clearance which will allow the oil to escape the rods that much better.
It wasn't too long ago that I thought there was only one bearing part number. But that proved wrong! Between the S85 and S65 lifespan there were a total of FOUR different bearing designs, but I believe only two of those ever saw production on the S65. The older designs are long gone and we'll never get a fresh set of those bearings to test and see how they differ from these (I already tried).
After I discovered the new bearing designs (702/703's), I thought they shared the same dimensions as the originals (088/089's). But that proved wrong too. These new measurements proved that the 702/703 bearings changed material, clearance, and pretty radically changed eccentricity.
By now I think I have a much clearer picture than when I started. Some will say (and have already said) that the 702/703 bearings changed dimensions because of the materials change. I've got to be honest, that sounds very compelling on the surface but there's one thing about it that really bugs me. Nobody has explained why the harder material would require extra clearance when 1) the bearing is never supposed to touch the journal, and 2) it would seem that it has less friction than the older lead/copper design. So to me, the dimensional changes of the new bearing weren't based on a simple materials change, but were much more deliberate.
The S65 started production with 088/089 bearings. But something was wrong: relatively new engines were puking connecting rods. The clearances were too tight, the side clearance was too tight, the eccentricity was too tight, and the oil was too thick. As a result, it seems like tolerance stack up with a bad luck of the draw, and your engine might end up looking like the photos shown above. So BMW decided to do something about it.
When BMW designed the newer 702/703 bearings to comply with lead-free regulations, they made changes. I believe they took steps to mitigate these problems. BMW increased the rod bearing clearance, and they increased the eccentricity by 250%. Those changes mean two of the four possible "trouble spots" I mentioned above have now been addressed.
In August 2013, BMW-NA made a specification change to the oil allowed in the S85/S65. After five years of only allowing 10W60, BMW relaxed the specifications and is now allowing LL-01 approved 0W40, 5W30, and 5W40 weight oils. Three of the four potential trouble areas we identified in the S65 have now been addressed. The only thing that remains is the rod side clearance. With the help of some buddies down the road, I might be able to take measurements on a wide range of BMW S65 crankshafts to see if the rod side clearance has changed throughout the three different crankshafts manufactured for the S65. If that comes to pass, I'll be sure to post the results either way (changed side clearance or not).
Van Dyne identified two of the four potential problems (journal clearance, rod side clearance), Kawasaki00 and BMWLVR were advocates for thinner oils, and we really kind of backed in to the eccentricity discussion and discovered a big change eccentricity clearances.
Some will say it's all a coincidence. They are just as entitled to their opinion as I am mine. I don't think it's a coincidence. For whatever reason, BMW changed (coincidence or not), BMW had three years with old bearing; then three years with new bearings; then changed to allow thinner oils. Sure it may all be a coincidence, but to me, it seems like they were chasing something and were making incremental changes to mitigate what they saw as a problem."
