Rod Bearings?

[Fin_f80]

Adding to the thread here are my rod bearings. ~115K miles on a 2015.

[papasmurf_m3]

If you've already removed them. I mean might as well. But, they're fine.

The internals don't slide on those bearings.Its the oil pressure that creates a layer in between the journals and the bearings. You get most wear at start up. When it's dry. But, once the car is on they dont touch. Even under extreme boost where that force is pushing heavily on those pistons its still not suppose to touch.

If your internals are just scraping the bearing like some might imagine you would have seized it a very long time ago. You can't have any metal to metal contact on an engine and survive. It would have thrown a rod out of the block.

If you would have left it alone it would have been just fine like all the rest. If you replace with new. I'm sure it will be fine. I get your worry. You're still fine.

No need to run down the street with your hair on fire about a problem that does not exist.

Used bearings are suppose to look like that. You open up any S55 and will likely look very similar.

[IamFODI]

Originally Posted by Jim45678

what paper hardness should I use?

Wow. Good question.

Can't imagine it'd matter much, though. Even "hard" bearing materials are pretty soft.

Originally Posted by Jim45678

PS: How many miles is proper brake-in period after rod bearings replacement? 1000 miles + oil change and I'm ready to hit redline?

my mechanic claims I should drive carefully for about 1500-1800 miles

I can tell you what Glyco has provided as a rule of thumb for at least some of their bearings. Glyco manufactures the second-gen OE bearings for the S65; not sure if yours are the same.

Source PDF is attached. On page 27 of the doc (page 14 of the PDF):

Where the maximum permissible engine rpm is nMax, the following running-in programme has been established:

step 1 1 Min 1/3 nMax
step 2 1 Min 1/4 nMax
step 3 1 Min 1/2 nMax
step 4 1 Min 1/3 nMax

During running-in, the engine performance should not exceed 15 to 20% of maximum load.

Can't say how applicable this is here. To the extent that it is applicable, it's hard to translate into miles as everyone's driving will be different.

It does seem to jive with other things I've heard from other manufacturers, though: don't go hard, and vary load and RPM, for at least a few hundred miles.

[Fin_f80]

Originally Posted by papasmurf_m3

If you've already removed them. I mean might as well. But, they're fine.

Used bearings are suppose to look like that. You open up any S55 and will likely look very similar.

I was doing some other work so just went ahead and replaced them.

[Joy15779]

Dear Mates. I speak after having the disaster. I was running stage 3 kratos turbo, 1.8 bar. Oil pump problem, one bearing hit a rod....
Now replaced bearings with stronger, carillo pistons and arrow rods. 2.0 bar safe and sound

[gerri]

Originally Posted by Jim45678

How many miles is proper brake-in period after rod bearings replacement? 1000 miles + oil change and I'm ready to hit redline?

my mechanic claims I should drive carefully for about 1500-1800 miles

BMW says 1200 miles for M cars, and in fact does break-in service at that point. Means that after that you can safely get to the red line.

[Alpine-F80]

I'm getting a 4-pin hub installed in a couple weeks, I'm wondering if I should ask them to look at the RB's?

Mainly wondering how much effort it is to inspect them with pan & VCG already off to drill crank? Guessing at that point you may as well replace them though...

~56k miles, '17 M3 6mt, 2nd owner, plan to run E85 tune eventually and keep car long time

[sly1types]

Originally Posted by Alpine-F80

I'm getting a 4-pin hub installed in a couple weeks, I'm wondering if I should ask them to look at the RB's?

Mainly wondering how much effort it is to inspect them with pan & VCG already off to drill crank?

How many miles on the car?

If they have they pan off, I can’t imagine it being more than $1k just to do them. I think they have to pull off some stuff to check one, it’s like windage tray or maybe the oil pump also.

[Alpine-F80]

Originally Posted by sly1types

How many miles on the car?

If they have they pan off, I can’t imagine it being more than $1k just to do them. I think they have to pull off some stuff to check one, it’s like windage tray or maybe the oil pump also.

Appreciate it. Car has ~56k miles. I didn’t plan to do crank hub but my pan is leaking oil so figured that’s an ideal time since subframe & pan is already coming off.

After more reading I’m most likely going to skip the RB’s. With all the high mileage & abused s55s out there it seems like a very low likelihood of failure. I’ll get my shop’s thoughts though

[jaylazy2020]

I had my crank hub done at 52k miles. It’s been superb since

As you say given the oil pan was off the incremental cost of doing the rod bearings would have been the lowest it could be and given that I plan to keep mine for another 3 years( I test drove a G82 today and didn’t like it all)

I would have gotten the rod bearings done had I know how long I plan to keep it.

58k miles now and driving from Stuttgart to Paris and then maybe Barcelona.

Stage 2 with dp and 102 Aral fuel in Germany. It really is epic and still such a great daily.

I would get them done

[Matt@Evolve]

We did a video on my 130,000 mile M4 for those wondering what the job involves.

[Alpine-F80]

Originally Posted by Matt@Evolve

We did a video on my 130,000 mile M4 for those wondering what the job involves.

Feeling better about NOT doing the bearings when I got my crank hub done

TL;DR seems to be don't worry about rod bearings, unless you're an EXTREMELY cautious individual, or already doing an engine build/rebuild. At 100k+ the bearings seem to have a lot of life left as long as the car has been well maintained.