Quote:
Originally Posted by RowanBuds
Yes, we in the F8x world have our little Crank Hub issue, but that hasn’t looked to be nearly as widespread of a concern as the RB S65 problems were/are. We’ve got forum members here at and above 75k miles on the platform, we’ve got members with 35-40k on FBO cars here, and we have others who are at 40+ track days on them. Large scale worrisome issues haven’t yet cropped up. The Crank Hub failures all look to be related to one of three things:
(1) Abusing the car – not letting it be warm before really honing, tons of kickdown downshifts etc.
(2) A very small number of bad torque specs leaving the factory
(3) Flash/JB4 tuning the car
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I'd like to add to this/modify this a bit.
On the S65, stock cars had rod bearings issues and BMW appears to have revised the rod bearings ~4x while maintaining the same part number.
On the S55, we have a very small handful of crank hub spins. Of that VERY SMALL NUMBER, almost none are stock (a few are). Of those FEW that are stock, they are DCTs. I'm not going to count a spun crank hub on a money shifted manual transmission car - I haven't read a credible report of a manual transmission stock s55 spinning a crank hub. Consider that about 1/3rd of S55s are spec'd with a manual transmission. Therefore, the issue shouldn't be considered a stock S55 issue - because it's not the S55 itself that causes it. Further, many SCH create timing issues - not engine replacement issues (some do cause engine replacement issues). If you accept that, then compare to the S65 and consider that the S65 had an integral engine issue, the S55 is ridiculously rock solid.
Of the overall very small number of spun crank hubs, they are overwhelming tuned. For whatever near unidentifiable reason, tuning is causing crank hubs to spin at a very small failure rate. And it's not directly proportional to power output.
I had an e39 m5 before my 2015 m3. The S62 in that is a legendary v8 engine - and that engine has questions around VANOS, rod bearings, oil consumption, weak stock clutch, and many more items.
By comparison the S55 is quite possibly the best stock M engine in terms of reliability, efficiency, output, tunability....the list goes on.
Not to be over the top, but it's going to be hard to top the S55 in terms of it's overall balanced excellence.