Check this out, I saved these pics off of FB where I saw a European restorer using this actual roller, not barrel bearing. I messaged him and he mentioned he always built engines this way. He said this was the original design for the war time R75 engine and allows the crank to move in & out rear main bearing inner race vs. entire bearing shifting in the rear carrier and wearing it out. Every engine I have rebuilt, 5 now, have needed new rear carriers dur to this wear. IIRC Zundapp engines use this bearing, and discussing this with some experienced, long time rebuilders, they mention they see no issue with using this setup bearing setup… I am even thinking about it myself! Discuss………
Well, the BMW /2 crankshafts flex quite a bit at higher rpm's. BMW even had to use the barrel bearing in the R68-R69S because of this. I don't know if a roller bearing would be able to cope with this flexing.
Unlike some engines, these boxers have the crank located by bearings at each end, with minimal ability to accommodate for the expansion of aluminum over steel. These use of a roller bearing at one end allows for such expansion. This approach assumes that the differential heat expansion is more important than the crank flex. It's hard to imagine that a roller bearing can tolerate or prevent much crank flexing. There are some that think the barrel bearing in the 69 engines can be replaced with a c3 ball bearing. lots of opinions, less data.
1960 NSU Supermax
1964 BMW R69S
1968 Triumph T100R road racer
1972 Triumph T150V road racer
2019 BMW S1000R
1967 R50/2….. here is a pic of the #. It is a single roller bearing.
This cannot be the correct bearing code. “rs” implies a rubber sealed bearing. It’s clearly not a sealed bearing. A couple of searches turn up a completely different sealed ball bearing.
The correct bearing code is NJ207E. Interesting is that they can limit axial movement in one direction but is open in the other(up to some max, maybe .020", just a wild guess).
1960 NSU Supermax
1964 BMW R69S
1968 Triumph T100R road racer
1972 Triumph T150V road racer
2019 BMW S1000R
The correct bearing code is NJ207E. Interesting is that they can limit axial movement in one direction but is open in the other(up to some max, maybe .020", just a wild guess).
Thanks. I’m not really seeing how this would provide any advantage over the normal barrel shaped roller bearing used in say.. an R69S.
If anything it would seem to allow LESS crank flex, and therefore more wear to the rear carrier.
I agree that the radial misalignment that crank flexing introduces might be kept in check by these bearing, but at the expense of having the rollers momentarily on edge when the flexing occurs. This roller misalignment, could induce brinneling if extreme, leading to early failure. Perhaps these bearings are not used on the engines with the most crank flex.
1960 NSU Supermax
1964 BMW R69S
1968 Triumph T100R road racer
1972 Triumph T150V road racer
2019 BMW S1000R