Technical Paper from Mahle explaining their Motorsport bearings for S65/85

[Adam M]

Really interesting leaflet from a proper oem supplier.

They also explain viable reasons for failure of stock bearings, discuss stock clearance and provide their solution.

Worth a read:

https://marmotorsport.com/wp-content...S85-Iss.-2.pdf

[Helmsman]

Thanks mate, interesting stuff.

[S85 builder]

Thanks for posting this. Confirms several things!

[HairTooLongToo]

I'm struggling to find clarity on anything.

If I had to summarize: the wear patterns are just the bearings doing their job to protect the crank. Our bearings will die in an admirable way because of our excellent material choices.

An explanation for the extent and rapidity of wear is the answers we want, and this doesn't really address that does it? Other than to say the wear is by design.

[PaulGros]

Originally Posted by HairTooLongToo

I'm struggling to find clarity on anything.

If I had to summarize: the wear patterns are just the bearings doing their job to protect the crank. Our bearings will die in an admirable way because of our excellent material choices.

An explanation for the extent and rapidity of wear is the answers we want, and this doesn't really address that does it? Other than to say the wear is by design.

Actually it does. "examination of mid-life OE bearings showed overlay corrosion to be a significant factor influencing bearing wear rate, as shown in Figure 1. Whilst corrosion is largely caused by oil degradation and operating temperature.... "

It's well documented and researched in peer reviewed engineering journals on why lead indium is a better overlay choice than lead / tin / copper.

[charliev68]

Did the end conclusion of the article say that the bearing clearances of the oem's are fine?

[PaulGros]

Originally Posted by charliev68

Did the end conclusion of the article say that the bearing clearances of the oem's are fine?

Yes it did. The OEM clearances are higher than originally believed and in line with other BMW engines.

[Adam M]

Two different points rolled up in that.

Mahle concluded there is nothing wrong with oem clearance.

Mahle stated the true clearance to be a higher value than many people have been claiming it is for years. I’m not sure how many people have taken in that the oem clearance is “normal” and no tighter than any other mass produced engine of note.

Just to confirm, mean clearance is 0.046mm.

[HairTooLongToo]

Originally Posted by PaulGros

Actually it does. "examination of mid-life OE bearings showed overlay corrosion to be a significant factor influencing bearing wear rate, as shown in Figure 1. Whilst corrosion is largely caused by oil degradation and operating temperature.... "

It's well documented and researched in peer reviewed engineering journals on why lead indium is a better overlay choice than lead / tin / copper.

Then can we draw the conclusion as follows?
- That the early bearings are defective as they are more prone to corrosion leading to accelerated wear.
- Whereas the later bearings don't (seem) to have this issue, and therefore, latter bearing changes are not of the same urgency as earlier. And upon change, extra clearance is not necessary.
- if you have changed bearings, assuming no other defects, it's going to last a while.

[PaulGros]

Originally Posted by HairTooLongToo

Then can we draw the conclusion as follows?
- That the early bearings are defective as they are more prone to corrosion leading to accelerated wear.
- Whereas the later bearings don't (seem) to have this issue, and therefore, latter bearing changes are not of the same urgency as earlier. And upon change, extra clearance is not necessary.
- if you have changed bearings, assuming no other defects, it's going to last a while.

No. Not at all. Early bearings are not defective. Corrosion is not a bearing problem but an operating environment problem. The corrosion effects the lead in the overlay, lead has been used in overlay since at least the 1940s.

Later bearings do not have the same corrosion problem as they are lead free. They are also harder so not as kind to the crank and have less seizure resistance due to the material used. Legislation forced the change, not improved performance.

If you have changed to lead copper bearings (which most aftermarket parts are) then if the same conditions exist you risk the same problem. If the bearings have a nickel dam (all except King GPC) then you may not see the damage as the bronze (copper) substrate may not be visible as the overlay will only be removed to the nickel layer. It's better for bronze to be exposed than nickel due to its tribological properties (small end bushes are often bronze) than nickel.

We still don't have an answer to the cause of the corrosion that MAHLE has identified.

[Brandoch]

I'm so glad that the rod and main bearing discussions are cohesive and clear.

[Ajolives]

[QUOTE=PaulGros;30946651]
We still don't have an answer to the cause of the corrosion that MAHLE has identified.

They spoke about corrosion several times in the excerpts you posted.

Whilst corrosion is largely caused by oil degradation and operating temperature....

That’s a fine enough answer for me. Operating environment providing a swell place for corrosion to hang out and eat away at precious millimeters of bearing material.

[Redd]

My key takeaways from the article were:

1. Wear showing copper is normal. The copper is an lubricating layer to protect the components. Mahle does say it is ok to replace the shells at that point.

2. Due to normal workshops not having the equipment and tolerances of a raceshop, it is ok to have more clearance for the bearings.

I'm not an engine expert but I am an engineer by education and interest. Corrosion wear does not bear friction marks at one specific area in one specific direction like we see on worn bearings. Only one thing does that - bearing to metal contact.

I think it's important to note that Mahle as the manufacturer of said bearings will of course present the information in a way that makes them look good. I work in Product Management and know when I'm reading a product brochure. So pardon me if I don't read the article the same way that some of you do.

[Ajolives]

Originally Posted by Redd

My key takeaways from the article were:

1. Wear showing copper is normal. The copper is an lubricating layer to protect the components. Mahle does say it is ok to replace the shells at that point.

2. Due to normal workshops not having the equipment and tolerances of a raceshop, it is ok to have more clearance for the bearings.

I'm not an engine expert but I am an engineer by education and interest. Corrosion wear does not bear friction marks at one specific area in one specific direction like we see on worn bearings. Only one thing does that - bearing to metal contact.

I think it's important to note that Mahle as the manufacturer of said bearings will of course present the information in a way that makes them look good. I work in Product Management and know when I'm reading a product brochure. So pardon me if I don't read the article the same way that some of you do.

It’s also important to note that Mahle did not specifically state all bearing failure causes are due to corrosion. This brochure was specifically targeted at the corrosion piece. I’m no engineer, switched to finance as one does, but I would think oil degradation/contamination is certainly a leading cause.

[drwankel]

Real world data would disagree with nearly everything mentioned here. Two facts to consider:

-99% of other engines bearings last the life of the engine.
-Everyone who has pulled out BE Bearings (which have increased clearance over stock) after 10s of thousands of miles of use has shown absolutely no wear on the bearings.

So I'm going with no, this paper is completely wrong. No Rod or main bearing should ever have to be replaced as preventative maintenance in any engine.

It's a design flaw, and one that the aftermarket has already fixed.

[PaulGros]

I'll post the same here as on M3cutters

Originally Posted by Redd

My key takeaways from the article were:

1. Wear showing copper is normal. The copper is an lubricating layer to protect the components. Mahle does say it is ok to replace the shells at that point.

No, that's not correct. The bronze (copper) can show if the overlay is damaged for any number of reasons. Bronze showing does not mean imminent failure if the bronze is undamaged.

Originally Posted by Redd

2. Due to normal workshops not having the equipment and tolerances of a raceshop, it is ok to have more clearance for the bearings.

Wrong again. When MAHLE Motorsport state "In motorsport, the engine assembly is very tightly controlled" they mean engines designed solely for racing i.e. F1, Moto GP, WRC etc. In this environment all relevant parts are controlled to within a very small range, and in some cases to the exact micron. Anything that replaces and OEM bearing they class as "performance aftermarket". It is nothing to do with the capability of the "shop" doing the work. The extra clearance Is effectively due to having a single grade part (as all other manufacturers) to ensure the part stays in tolerance. We could ask MAHLE to produce graded bearings as per OE, but this would mean each engine would need crank and housing measured to select the correct parts. This wouldn't work. But if any distributor WANTS to do this then for sure the parts can be made. If it was wanted the parts could be manufactured to exact size with no deviation (tolerance) with individual serial numbers.

Originally Posted by Redd

I'm not an engine expert but I am an engineer by education and interest. Corrosion wear does not bear friction marks at one specific area in one specific direction like we see on worn bearings. Only one thing does that - bearing to metal contact.

Many innovations in engineering have been by people without a formal engineering degree :-) MAHLE has not stated that this is the ONLY failure made. I'm sure there are bearings out there where metal to metal contact has occurred. The fact remains, all parts examined showed overlay loss due to corrosion. The isn't anything unknown, feel free to research this subject, as well as the benefits of lead indium as an overlay vs lead tin copper. This subject has been discussed many times in peer reviewed papers and engineering journals.

I'm happy to put your theories to MAHLE for discussion, just drop them here or in a private message.

Originally Posted by Redd

I think it's important to note that Mahle as the manufacturer of said bearings will of course present the information in a way that makes them look good. I work in Product Management and know when I'm reading a product brochure. So pardon me if I don't read the article the same way that some of you do.

An interesting point. Glacier Vandervell (Now MAHLE) was the manufacturer of the bearings. However, until I released that information it was generally incorrectly assumed it was Clevite. Why would MAHLE correct this misunderstanding and then release information explaining the data? Surely it would be easier to leave everyone assuming MAHLE was nothing to do with the original parts? Given this part represents around 0.0001% of global turnover and the OE part has been out of production for around 14 years I really don't see what they stand to gain?

The document is written by one of the Race Unit engineers. He is not a marketing person and the document has not even been viewed by anyone in MAHLE marketing. The document is written as he talk. An earlier draft had additional information, including a section on the BMW grading system. Ultimately he thought it was starting to get a little too in depth as the goal was to try and present the information that would be easily understandable even to those without engineering knowledge. Maybe judge the document on its data rather than tone, of course after independently researching and validating it.

[PaulGros]

Originally Posted by Ajolives

It’s also important to note that Mahle did not specifically state all bearing failure causes are due to corrosion. This brochure was specifically targeted at the corrosion piece. I’m no engineer, switched to finance as one does, but I would think oil degradation/contamination is certainly a leading cause.

It wasn't specifically target at corrosion. The document originated as I called in a favour for a Race Unit engineer to take a look at a set of bearings supplied by a user on another forum (he's also active here) hoping to get some clarity on the "issues" from an engineering point of view.

I raised questions on a call with him on the unusual wear pattern, specifically in the parting line on the bearing where the largest clearance is due to counterboring missing the overlay. This in itself put a very big question mark on clearance being the issue. I initially suspected excessive crush had caused the bearing to distort, but on examination this was not the case. The explanation on the parting line missing overlay starts to go above my head. The basic explanation is the way the overlay is plated there are greater concentrations of lead in this area. As it is the lead that is attacked, this area can show more corrosion.

It transpired that other bearings have been examined and are in the MAHLE database with the same issue. All have shown overlay corrosion. Now I'm sure there are bearings out there that have failed for other reasons, they are not covered here as they have not seen samples.

[PaulGros]

Originally Posted by drwankel

Real world data would disagree with nearly everything mentioned here. Two facts to consider:

-99% of other engines bearings last the life of the engine.
-Everyone who has pulled out BE Bearings (which have increased clearance over stock) after 10s of thousands of miles of use has shown absolutely no wear on the bearings.

So I'm going with no, this paper is completely wrong. No Rod or main bearing should ever have to be replaced as preventative maintenance in any engine.

It's a design flaw, and one that the aftermarket has already fixed.

Sure you're allowed to disagree, that's the beauty of forums and the way we all learn.

I'd be interested in facts to support your argument, and I would also be happy to put your data to MAHLE for comment.

I would ask, if it was a design flaw then why has BMW not issued a recall? Also when the parts moved to lead free with a different manufacturer the same specs appear to have been kept? I don't have access to the Glyco drawing to confirm this, but measurements of OE parts would strongly suggest they are in line.

Regarding the aftermarket fix, I've run average wall thickness data for all bearings in the BE Wiki. If you do the same it will show some interesting results on where they all sit with sizing.

[Helmsman]

Originally Posted by PaulGros

Regarding the aftermarket fix, I've run average wall thickness data for all bearings in the BE Wiki. If you do the same it will show some interesting results on where they all sit with sizing.

Hi Paul, good to see you here as well...

Might be my poor English again, more specifically what do you refer to here?

Cheers
Nik

[Green-Eggs]

Originally Posted by PaulGros

Regarding the aftermarket fix, I've run average wall thickness data for all bearings in the BE Wiki. If you do the same it will show some interesting results on where they all sit with sizing.

Those measurements were in the process of being updated with his new air gauge when Bert got side tracked and building a new house. All measurements up to the BE shells were probably done on a ball-anvil micrometer, which may not be the most accurate way to measure. That's why he was in the process of redoing them. The air gauge rig is supposedly accurate to 0.000001 inch. I know he measured the Mahle Motorsport shells with it, and sent the results to either you or Alan, maybe both. So, it would be interesting to see how your measurements compare with those, and at least the BE Shells on the wiki. Would also like to know your measurement methodology and equipment if possible. More data, is better.

While we're at it, maybe M Power Motorsport will share his measurement accuracy, variance, resolution, stepper motor resolution, cosine error (which is probably 0, but nice to know). I'm really surprised nobody is asking these questions about that rig.

[PaulGros]

Originally Posted by Helmsman

Hi Paul, good to see you here as well...

Might be my poor English again, more specifically what do you refer to here?

Cheers
Nik

S65 bearings is taking over my life

If you take the average wall thickness for each bearing in the WIKI, you will see either the data is wrong or if it is correct all bearings are surprisingly very close except the HX ACL & the VAC Clevite. This is no surprise as they are 0.025mm additional clearance.

The Wiki states the VAC parts are standard clearance, the picture states other wise - they are clearly marked HX and the measurements support this.

[Helmsman]

Originally Posted by PaulGros

S65 bearings is taking over my life

If you take the average wall thickness for each bearing in the WIKI, you will see either the data is wrong or if it is correct all bearings are surprisingly very close except the HX ACL & the VAC Clevite. This is no surprise as they are 0.025mm additional clearance.

The Wiki states the VAC parts are standard clearance, the picture states other wise - they are clearly marked HX and the measurements support this.

Haven't looked into the BE page for long (and it has been gone for a while), but you mean wall thickness between the shells are pretty much the same incl BE? (again, except for the extended)