Pls help with recent E90 M3 Rod bearing replacement

[Rjacutin]

I have a quick question regarding a recent RB replacement. I was hoping that somebody would be able to answer it since most of us are baffled we couldn’t figure out what it is. so I have a 2008 E90 m3 with 116k on it, Upon replacing the rod bearings, cylinder 2 has the most wear on it that it shows the copper layer. The copper layer was smooth with no chipping. Upon inspecting the crank journal and the bearing itself, there was no scoring on the journals or damage to it. I took some pictures of the bearings from cylinder 1 through 8. I noticed that the bearing that has the most wear which is cylinder 2...the backside of it was shinier than the others. I examined it closely and found out that the shiny part was actually a wear that also shows the copper layer on the sides of the backside of the bearing. The bearing didn’t Spun or move out of its place because the tabs/notches are intact and doesn’t have any wear or marks on them.

Now, my question at this point is: why is there wear on the backside of the bearing when the bearing did not spun?? the tabs/notches are fine. Is there any play on it? defective connecting rods etc.??

Attached are the photos of all the bearings. particularly the cylinder 2 bearings and its close-up pictures.

Your reply is greatly appreciated, thank you very much

[pbonsalb]

I’d say you are lucky you changed them. Looks like #2 spun.

[Scharbag]

Was the rod cap damaged at all? A spun bearing will ruin the rod as the alignment tang spins around machining a nice groove. You said the tang was in place an nothing moved so maybe you got lucky.

If the rod was undamaged, I would say you are one lucky person as #2 was moments away from destroying your engine. #3 was looking angry too.

Those bearings look terrible BTW.

[SYT_Shadow]

that really looks terrible. So much for 'if you get to 100k miles you're all set' nonsense...

Interested in what deansbimmer thinks, he's seen many more of these than I

[nycplumber]

You won the bearing lottery that's for sure. Make sure you enjoy a nice relaxing weekend because if things went different you would never forget about Columbus day weekend for the rest of your life.

[aswy6]

Holy crap you just won a lottery

[mrdoja]

That bearing was ready to cut loose, footloose....SORRY..YOU are lucky my friend!

[kawasaki00]

You are one lucky guy. The shells did not spin as evidence by the dark mark to the bottom of the tang on the first pic. If it had turned the tang would have a shiny mark on the bottom side and that dark area would be kind of scuffed away looking.
From the dents on the other shell there was either debris in the rod or on the back of the shell when the engine was first assembled. Making clearance really tight in those couple spots is why you see the bad wear marks in the same area. Hopefully the debris whatever it was has been cleaned away before the new shells went in.
Have seen a few blow up with less than that so you are fortunate for sure.
The green circles are the fret marks when the backing of the shell isnt always touching the rod. The shell moves around inside the rod and just grinds those marks into the backing plate. That usually transfers a small amount of material to the rod in the process.
Bet if you look at the parting line of that shell there are marks where it wasnt evenly clamped all the way across.
Cheers

[M3ANMACHINE]

WOW! Very lucky indeed.

Curious what Malek@MRF thinks about this

[deansbimmer]

Kawasaki00 has it.

I don't usually see signs of assembly debris on the back of factory installed shells.
Definitely on the verge of total failure. You got lucky.

[ycb]

how did you know to change them? any oil analysis?

[Honda]

wow.. those look terrible bad. One of the worse I have seen so far.

You are really lucky it didn’t spun at this mileage. You should celebrate

[alpina-527]

Are those shells in the photo aftermarket? They don't look like original BMW from here.

[pbonsalb]

I think Clevite 712/713 are original BMW.

[deansbimmer]

They are BMW shells. Clevite 113 stamps are BMW's early 088/089 bearings from 2007 to mid 2010 mfg. 702/703 are the later bearings.

[alpina-527]

Originally Posted by deansbimmer

They are BMW shells. Clevite 113 stamps are BMW's early 088/089 bearings from 2007 to mid 2010 mfg. 702/703 are the later bearings.

Aah. Thanks for clearing that up