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02-29-2024, 08:35 AM | #1 |
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Technical Paper from Mahle explaining their Motorsport bearings for S65/85
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 |
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02-29-2024, 01:02 PM | #4 |
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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. |
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charliev68203.50 |
02-29-2024, 01:17 PM | #5 | |
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It's well documented and researched in peer reviewed engineering journals on why lead indium is a better overlay choice than lead / tin / copper. |
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02-29-2024, 02:42 PM | #7 |
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charliev68203.50 |
02-29-2024, 02:55 PM | #8 |
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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. |
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02-29-2024, 03:32 PM | #9 | |
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- 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. |
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02-29-2024, 03:59 PM | #10 | |
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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. |
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02-29-2024, 06:05 PM | #12 |
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[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. |
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02-29-2024, 06:09 PM | #13 |
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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. |
02-29-2024, 06:20 PM | #14 | |
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02-29-2024, 06:30 PM | #15 |
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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. |
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03-01-2024, 04:22 AM | #16 | ||||
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I'll post the same here as on M3cutters
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I'm happy to put your theories to MAHLE for discussion, just drop them here or in a private message. Quote:
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. |
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03-01-2024, 04:37 AM | #17 | |
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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. |
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03-01-2024, 07:43 AM | #18 | |
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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. |
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03-01-2024, 08:33 AM | #19 | |
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Might be my poor English again, more specifically what do you refer to here? Cheers Nik |
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03-01-2024, 08:40 AM | #20 | |
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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. |
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03-01-2024, 09:32 AM | #21 | |
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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. |
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03-01-2024, 09:51 AM | #22 | |
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