Official S65 Rod Bearing Condition Example Thread

[doogee]

Everyone calm your panties. We already knew the OEM bearing with a coating wouldn't be any good.

Just let the examples keep rolling in.

[pbonsalb]

Actually, someone removed a set of oem bearings with the vac calico coating after 13k miles and they looked perfect.

[nycplumber]

Originally Posted by pbonsalb

Actually, someone removed a set of oem bearings with the vac calico coating after 13k miles and they looked perfect.

With oem bolts too?

[Doc Oc]

Nope, ARP that comes with the vac kit...

[anerbe]

Originally Posted by Doc Oc

Nope, ARP that comes with the vac kit...

Based on the autotalent pics,
- OEM coated bearings with OEM bolts are not a good combo - way too much wear at only 1500.
- Considering Doc Oc had the same exact 702/703 bearings using ARP-2K bolts, they were perfect with about 10x the amount of miles.

Assuming no other crazy variances in play - perhaps it's a combination of too tight clearances of the bearing and eccentricity/bearing crush caused by the bolts as Malek has pointed out. I would love to see either VAC or BE bearing pictures with OEM bolts that is uninstalled after 15-30K miles. I would also love to see examples of ARP bolts used with OEM bearings (highly unlikely). Maybe there's some sort of multifactorial issue, where OEM bolts can be used with a certain amount of higher clearance, or OEM bearings can be used with ARP bolts...and best case scenario is extra clearance bearings with ARP bolts.

We need more data / studies!

[BrewRifle]

Originally Posted by anerbe

Based on the autotalent pics,
- OEM coated bearings with OEM bolts are not a good combo - way too much wear at only 1500.
- Considering Doc Oc had the same exact 702/703 bearings using ARP-2K bolts, they were perfect with about 10x the amount of miles.

Assuming no other crazy variances in play - perhaps it's a combination of too tight clearances of the bearing and eccentricity/bearing crush caused by the bolts as Malek has pointed out. I would love to see either VAC or BE bearing pictures with OEM bolts that is uninstalled after 15-30K miles. I would also love to see examples of ARP bolts used with OEM bearings (highly unlikely). Maybe there's some sort of multifactorial issue, where OEM bolts can be used with a certain amount of higher clearance, or OEM bearings can be used with ARP bolts...and best case scenario is extra clearance bearings with ARP bolts.

We need more data / studies!

I'd be happy to be the guinea pig for the BE bearings with OEM bolts uninstall if someone were to pay for it . I've been running this combination for almost a year now without issue.

[deansbimmer]

Since there are examples of VAC bearings that look horrible and some that look great, some engines grenading with untouched bearings at 15k miles and some finally at 115k miles, why would we not suspect variances in BMW manufacturing tolerances on the crankshaft journals themselves?

[anerbe]

Originally Posted by BrewRifle

I'd be happy to be the guinea pig for the BE bearings with OEM bolts uninstall if someone were to pay for it . I've been running this combination for almost a year now without issue.

Haha don't look for me to fund the experiment!

[anerbe]

Originally Posted by deansbimmer

Since there are examples of VAC bearings that look horrible and some that look great, some engines grenading with untouched bearings at 15k miles and some finally at 115k miles, why would we not suspect variances in BMW manufacturing tolerances on the crankshaft journals themselves?

True! With so many variables on very tight tolerances, all involved parts and their variation could cause this. I'm hoping with all the data from rod and crankshaft journal measurements collected so far, that these can hopefully be considered insignificant compared to the bearing and rod bolt variations we are trying to understand.

If at the end of the day the OEM journals have too much variation to determine a proper fix, simple bearings swaps done now are still at risk and the only true way to prevent it would be a full engine rebuild with measured/machined crankshafts, etc...

I guess we are still all hoping this isn't the case.

[drrust]

Originally Posted by anerbe

Haha don't look for me to fund the experiment!

This whole problem screams for some finite element analysis. Unfortunately it seems most of the published literature is not freely available. Much of the work was done in the 1990's so it is not clear who is modeling these systems today. It would be cool to see the S65 design modeled with different clearances.

Here is an example:

https://people.rit.edu/~sxbeme/REEF%20boedo-booker.pdf

There are many more studies that are in pay to see journals that are copyrighted.

In looking at the surfaces of the bearings from my 09, there was uneven wear & some with a small amount of wear looked to have 'pull out' rather than localized wear.

[admranger]

Originally Posted by drrust

In looking at the surfaces of the bearings from my 09, there was uneven wear & some with a small amount of wear looked to have 'pull out' rather than localized wear.

By "pull out" do you mean pitting or something else? I had pits on my 2011 bearings. Just pulled another forum member's bearings yesterday and he had far fewer pits, but some nevertheless. Really odd looking under magnification.

[drrust]

Originally Posted by admranger

By "pull out" do you mean pitting or something else? I had pits on my 2011 bearings. Just pulled another forum member's bearings yesterday and he had far fewer pits, but some nevertheless. Really odd looking under magnification.

The 'pull out' looks like there is a step in the coating rather than a smooth transition that one would expect from a pure wear. Maybe cavitation or surface fatigue.

[anerbe]

I've seen some of the "pull out" characteristics on the edges, where perhaps chunks of the lead/copper detached from the bearing - these pieces could have rotated in the bearing surface leading to the circumferential scoring or pitting.

[SYT_Shadow]

Originally Posted by anerbe

If at the end of the day the OEM journals have too much variation to determine a proper fix, simple bearings swaps done now are still at risk and the only true way to prevent it would be a full engine rebuild with measured/machined crankshafts, etc...

There's no need to live in fear. When you do your rod bearings, plastigage every one. It isn't hard and you'll have your answer

The DIY I posted covers how to plastigage

[anerbe]

Originally Posted by SYT_Shadow

There's no need to live in fear. When you do your rod bearings, plastigage every one. It isn't hard and you'll have your answer

The DIY I posted covers how to plastigage

I agree with you - my comment was to reinforce that we can't be 100% certain with the reasonable prevention measures of swapping rod bearings alone. However, it's our best option as preventative.

A true fix of rebuilding is unreasonable in terms of costs to be considered as a preventative measure (addressing rod and mains bearings).

[Bmw doubles]

Amazing thread and contributions! This is telling me if I buy a used M3 plan on including another 2-3k in bearing replacement on top of the purchase :/ regardless of miles

[doogee]

Originally Posted by Bmw doubles

Amazing thread and contributions! This is telling me if I buy a used M3 plan on including another 2-3k in bearing replacement on top of the purchase :/ regardless of miles

Unfortunately that's the situation with these motors. While mine have been done, I still have the worry of the main bearings in the back of my head. I'll have to do them at some point.

[Bmw doubles]

Originally Posted by doogee

Unfortunately that's the situation with these motors. While mine have been done, I still have the worry of the main bearings in the back of my head. I'll have to do them at some point.

What's your mileage?

[doogee]

Originally Posted by Bmw doubles

What's your mileage?

160,000 KM or 100,000 Miles.

I've put about 30,000 KM (20,000 Miles) on my VAC bearings.

[SDPLV]

Originally Posted by doogee

Unfortunately that's the situation with these motors. While mine have been done, I still have the worry of the main bearings in the back of my head. I'll have to do them at some point.

Main bearings?

[doogee]

Originally Posted by SDPLV

Main bearings?

They tend to show quite a bit of wear as well when these engines are pulled apart.

[SDPLV]

Originally Posted by doogee

They tend to show quite a bit of wear as well when these engines are pulled apart.

I don't see any Main Bearing Example thread. Are we starting that trend as well? Maybe we can draw pics of what we think they look like.