Blown motors, Rod Bearing failure S65 Registry.

[Sneaky Pete]

Originally Posted by PaulGros

27 total? Or 27 for mains? sorry for not checking, I'm sure Assimilator1 will share his data for review when it's finished.

So I control + F for the keyword Main in Assimilators list of broken engines and found 27 that had the word Main.
It would take a lot longer to verify each entry but the number gives a rough idea of the number.

[Assimilator1]

Originally Posted by PaulGros

27 total? Or 27 for mains? sorry for not checking, I'm sure Assimilator1 will share his data for review when it's finished.

Their have been 30 confirmed recorded main bearing failures in the list for this thread (I updated it a few days ago), plus a further 6 likely due to mains failure.

The data is already here in this thread (see the 3rd link in my sig for a direct link to it), it just hasn't been put into a spreadsheet to be able to easily sort different attributes.

SneakyPete
It may be just coincidental that main bearing failures became much more prevalent after the increased clearance bearings came onto the market but I suspect that it is not.

I suspect it is, for 2 reasons, since 2016 (I think that's when increased bearings came out?) all cars have clocked many more miles, so any type of failure will be on the increase.
And the majority of the engines with mains failures have had standard rod bearings, only a few had increased clearance bearings.
One of which I recall is SYT_Shadow's car

Afraid I don't recall the others, and I didn't record them as the instances were so few I didn't think it worth it/relevant.
But if you or someone else would like go through the mains failures list and find those others ones, I'll add the info in (I've just added it in for SYT's car).

[edit] update list, removed Lexshive from uncertain list, bearings hadn't failed.
Moved chamoloco from uncertain list to 'likely rod bearings' list after realising I'd mis-read his 'top bearing' comment.

[Helmsman]

Originally Posted by Assimilator1

Their have been 30 confirmed recorded main bearing failures in the list for this thread.

And the majority of the engines with mains failures have had standard rod bearings, only a few had increased clearance bearings.

Taking the libery to cut out the key bit.
Thanks for coming back to this Mark, as extended RBs is suggested by Pete to be the main reason for the main bearings to fail.

Cheers
Nik

[Sneaky Pete]

Originally Posted by Helmsman

Taking the libery to cut out the key bit.
Thanks for coming back to this Mark, as extended RBs is suggested by Pete to be the main reason for the main bearings to fail.

Cheers
Nik

I wasn't making any wild statements only my suspicion....and I'm not the only who has these doubts.
By 2016 there were no main bearing failures..now there are between 30-36.
If I had the energy I would go back through the post history of each main bearing failure but TBH I can't be bothered.

As long as folk are hanging onto the idea than the OEM RB clearance was incorrect then any contrary theories will continue to be dismissed.

[M3SQRD]

Originally Posted by Sneaky Pete

I wasn't making any wild statements only my suspicion....and I'm not the only who has these doubts.
By 2016 there were no main bearing failures..now there are between 30-36.
If I had the energy I would go back through the post history of each main bearing failure but TBH I can't be bothered.

As long as folk are hanging onto the idea than the OEM RB clearance was incorrect then any contrary theories will continue to be dismissed.

Eight years is a long time. If each car was driven the average 14k miles per year that means since 2016 cars have accumulated, on average, 112k additional miles. deansbimmer has shown pictures showing wear on main bearings. Unlike RBs, he’s seen main bearings wearing much more slowly than RB (no matter what the root cause of RB is/are). An average of 112k additional miles + existing mileage in 2016 would put the total mileage in the range wear main bearings will likely fail, regardless of which RB were in the car. If aftermarket RBs were the primary cause of main bearing failure, you should’ve seen a much higher number than 30 total known failures since 2016. When you read FS threads, you’ll notice that the majority of cars FS have had their RBs replaced.

[Sneaky Pete]

Originally Posted by M3SQRD

Eight years is a long time. If each car was driven the average 14k miles per year that means since 2016 cars have accumulated, on average, 112k additional miles. deansbimmer has shown pictures showing wear on main bearings. Unlike RBs, he’s seen main bearings wearing much more slowly than RB (no matter what the root cause of RB is/are). An average of 112k additional miles + existing mileage in 2016 would put the total mileage in the range wear main bearings will likely fail, regardless of which RB were in the car. If aftermarket RBs were the primary cause of main bearing failure, you should’ve seen a much higher number than 30 total known failures since 2016. When you read FS threads, you’ll notice that the majority of cars FS have had their RBs replaced.

You could well be right, its may just be simple wear and tear.
And I guess so many owners having been duped into believing that the OEM rod bearing clearance was too tight, would be reluctant to believe a new scare under the well known scientific principle of once bitten twice shy.

Yet does it not make you wonder...when you fit rod bearings with extra clearance which allows oil to flow much more easily out of the bearings...and oil will always flow towards the point of least resistance...is there no possibility that the unintended consequence of fitting these under sized rod bearings bearings will be reduced flow through the main bearings?

Anyway honestly not bothered...having already spent too much time over the last 10 years trying to convince people that the whole too tight clearance theory was nonsense...it became obvious that folk will often believe whatever they like even when it doesn't pass the simple common sense test.

[M3SQRD]

Originally Posted by Sneaky Pete

You could well be right, its may just be simple wear and tear.
And I guess so many owners having been duped into believing that the OEM rod bearing clearance was too tight, would be reluctant to believe a new scare under the well known scientific principle of once bitten twice shy.

Yet does it not make you wonder...when you fit rod bearings with extra clearance which allows oil to flow much more easily out of the bearings...and oil will always flow towards the point of least resistance...is there no possibility that the unintended consequence of fitting these under sized rod bearings bearings will be reduced flow through the main bearings?

Anyway honestly not bothered...having already spent too much time over the last 10 years trying to convince people that the whole too tight clearance theory was nonsense...it became obvious that folk will often believe whatever they like even when it doesn't pass the simple common sense test.

If wear rates were the same between RB and main bearings then that might be the case. However, it’s been shown that main bearings do not wear as fast as RBs. If it did then we would have seen many main bearing failure at low mileage.

If it were due to extra clearance RB and a slight reduction in oil pressure, why would Mahle, even after their review and conclusion regarding OEM RBs, release RBs with a similar nominal clearance to BE RB nominal clearance (in particular with BE V1 nominal clearance, which is what most people are using)?

[Sneaky Pete]

Originally Posted by M3SQRD

If wear rates were the same between RB and main bearings then that might be the case. However, it’s been shown that main bearings do not wear as fast as RBs. If it did then we would have seen many main bearing failure at low mileage.

If it were due to extra clearance RB and a slight reduction in oil pressure, why would Mahle, even after their review and conclusion regarding OEM RBs, release RBs with a similar nominal clearance to BE RB nominal clearance (in particular with BE V1 nominal clearance, which is what most people are using)?

I would imagine that when a manufacturer is designing a new engine, a certain amount of effort would be put into getting the right balance of oil flow between the rod and main bearings...not expecting owners to then later alter that balance.

One of the interesting findings on engine failures back in the day was the comparison between the UK and the USA engine failure rates due rod bearings.
At the start of 2016 there had been 2 RB engine failures in the UK found on M3cutters. A subsequent poll held on M3cutters a couple of years later did not reveal any further pre 2016 failures.
Noting that the UK (Pop ~69m) was the biggest per capita market for E9x M3s outside of Germany.
In the same time frame there had been 14 RB engine failures recorded on M3post for California (Pop~39m).
A difference sufficient that it ought to indicate the reason why this particular BMW engine suffers a far higher rate of failure in the USA compared to the UK.....as well as previous gen M cars with the same clearance.

Mahle would be better placed to answer questions on their choice of Rod Bearing clearance. But its my understanding that their clearance is only very slightly higher than the OEM clearance and was to allow the use of a single sized bearing rather than the two OEM bearings with 2 colour codes. Plus of course no point in trying to sell rod bearings at OEM clearance when most everyone has been duped into believing that clearance is too tight.

I would have thought that Mahle revealing that the OEM rod bearing clearance was pretty much standard, ought to have triggered a complete rethink on the issue.

Certainly if I still had my E92 M3 I would use (later non lead faced) OEM spec rod bearings and not extra clearance ones if I decided to swap them out as a preventative measure.

[M3SQRD]

Originally Posted by Sneaky Pete

I would imagine that when a manufacturer is designing a new engine, a certain amount of effort would be put into getting the right balance of oil flow between the rod and main bearings...not expecting owners to then later alter that balance.

One of the interesting findings on engine failures back in the day was the comparison between the UK and the USA engine failure rates due rod bearings.
At the start of 2016 there had been 2 RB engine failures in the UK found on M3cutters. A subsequent poll held on M3cutters a couple of years later did not reveal any further pre 2016 failures.
Noting that the UK (Pop ~69m) was the biggest per capita market for E9x M3s outside of Germany.
In the same time frame there had been 14 RB engine failures recorded on M3post for California (Pop~39m).
A difference sufficient that it ought to indicate the reason why this particular BMW engine suffers a far higher rate of failure in the USA compared to the UK.....as well as previous gen M cars with the same clearance.

Mahle would be better placed to answer questions on their choice of Rod Bearing clearance. But its my understanding that their clearance is only very slightly higher than the OEM clearance and was to allow the use of a single sized bearing rather than the two OEM bearings with 2 colour codes. Plus of course no point in trying to sell rod bearings at OEM clearance when most everyone has been duped into believing that clearance is too tight.

I would have thought that Mahle revealing that the OEM rod bearing clearance was pretty much standard, ought to have triggered a complete rethink on the issue.

Certainly if I still had my E92 M3 I would use (later non lead faced) OEM spec rod bearings and not extra clearance ones if I decided to swap them out as a preventative measure.

Mahle - 0.055mm
BE V1 - 0.0597 mm
BE V2 - 0.0681 mm

[Helmsman]

Originally Posted by Sneaky Pete

I would imagine that when a manufacturer is designing a new engine, a certain amount of effort would be put into getting the right balance of oil flow between the rod and main bearings...not expecting owners to then later alter that balance.

Hi Pete. My understanding is that BMW matched the couple of different shells sizes/colour with shaft/housing when building the engine. I.e. not possible to do really when for what ever personal reason replacing the bearing, hence increased clearance to avoid risk going too tight.

Originally Posted by Sneaky Pete

Mahle would be better placed to answer questions on their choice of Rod Bearing clearance. But its my understanding that their clearance is only very slightly higher than the OEM clearance and was to allow the use of a single sized bearing rather than the two OEM bearings with 2 colour codes. Plus of course no point in trying to sell rod bearings at OEM clearance when most everyone has been duped into believing that clearance is too tight.

Pete, you not yet even bothered to read into MAHLE's numbers? After using MAHLE's statement as proof that the theory of too tight clearance is BS, you at the same time suggest that MAHLE are forced to sell extended shells as well in order to align to a deluded the market? Now that is getting a tad hearty even for you mate...

Originally Posted by Sneaky Pete

Certainly if I still had my E92 M3 I would use (later non lead faced) OEM spec rod bearings and not extra clearance ones if I decided to swap them out as a preventative measure.

Yeah some time since you had an your own E9x M3 now Pete. The one you had blow up due to a spun RB, IIRC?

Cheers,
Nik

[Sneaky Pete]

Originally Posted by Helmsman

Hi Pete. My understanding is that BMW matched the couple of different shells sizes/colour with shaft/housing when building the engine. I.e. not possible to do really when for what ever personal reason replacing the bearing, hence increased clearance to avoid risk going too tight.

Pete, you not yet even bothered to read into MAHLE's numbers? After using MAHLE's statement as proof that the theory of too tight clearance is BS, you at the same time suggest that MAHLE are forced to sell extended shells as well in order to align to a deluded the market? Now that is getting a tad hearty even for you mate...

" After using MAHLE's statement as proof that the theory of too tight clearance is BS"
Is it not proof?
And I thought I quoted Pauls reason why Mahle supply bearings of the size they do (one size rather than 2). In addition to the pragmatism of demand and supply.

Originally Posted by Helmsman

Yeah some time since you had an your own E9x M3 now Pete. The one you had blow up due to a spun RB, IIRC?
Cheers,
Nik

Right its some time since I sold my second £92 M3...does that somehow disqualify me from commenting?
Now it didn't spin a RB...I traded it in for a new F82 M4.
If you don't believe me I guess I can find the receipt from the BMW dealer who did the trade.

[PaulGros]

Originally Posted by Sneaky Pete

" After using MAHLE's statement as proof that the theory of too tight clearance is BS"
Is it not proof?
And I thought I quoted Pauls reason why Mahle supply bearings of the size they do (one size rather than 2). In addition to the pragmatism of demand and supply.


Right its some time since I sold my second £92 M3...does that somehow disqualify me from commenting?
Now it didn't spin a RB...I traded it in for a new F82 M4.
If you don't believe me I guess I can find the receipt from the BMW dealer who did the trade.

To be clear, MAHLE Motorsport clearance is based purely on their calculations for their material and to compass all crank and housing sizes with a single grade. It is nothing at all to do with others offering "extended clearance" and this wasn't even considered in the design stage.

[PaulGros]

Originally Posted by M3SQRD

Mahle - 0.055mm
BE V1 - 0.0597 mm
BE V2 - 0.0681 mm

But only one of those is caculated from the actual print data.

As far a I am aware the BE figures are from a measured set. How do you know they were in spec to the print? As far as I am aware, BE has not published their wall thickness data or tolerance from the print. And yes, this is something I have spoken to Robert about.

I do have min & max wall thickness data from prints for MAHLE Motorsport, ACL and I'm waiting on the same from King. Only the print data will show for sure the nominal clearance each company is targeting. We can then use the BE measurements to see how close each is in reality I.e. How well each company is controlling tolerances.

[PaulGros]

Originally Posted by Sneaky Pete

Mahle would be better placed to answer questions on their choice of Rod Bearing clearance. But its my understanding that their clearance is only very slightly higher than the OEM clearance and was to allow the use of a single sized bearing rather than the two OEM bearings with 2 colour codes. Plus of course no point in trying to sell rod bearings at OEM clearance when most everyone has been duped into believing that clearance is too tight.

There are plenty rod bearings sold in the market with clearances that are nominally the same as BMW OEM. Now whether people actually realise they are the same is a different question

MAHLE Motorsport wouldn't produce a part based on anything but their own data. You may notice that they are the only producer of race bearings that isn't producing an extra clearance part for any application they have in range.

[M3SQRD]

Originally Posted by PaulGros

But only one of those is caculated from the actual print data.

As far a I am aware the BE figures are from a measured set. How do you know they were in spec to the print? As far as I am aware, BE has not published their wall thickness data or tolerance from the print. And yes, this is something I have spoken to Robert about.

I do have min & max wall thickness data from prints for MAHLE Motorsport, ACL and I'm waiting on the same from King. Only the print data will show for sure the nominal clearance each company is targeting. We can then use the BE measurements to see how close each is in reality I.e. How well each company is controlling tolerances.

I do not know the history behind each set of nominal dimensions and whether the individual RBs used were within spec. How would I? Same thing applies to Mahle, ACL, King, etc. I personally do not have released engineering/manufacturing drawings from a single RB manufacturer. Just like with any product you buy, you have faith/trust that the item you’re buying was manufactured and assembled within allowable tolerances and it satisfies all requirements/specs. I don’t request a complete set of drawings from BMW and then personally verify every piece part, subassembly and the final assembled car are all within their respective specs/tolerances/requirements before I purchase a car. I trust BMW has manufactured the car to meet all of its requirements/specs. So, for RB nominal clearance whether right or wrong, I have faith that the published nominal values for each manufacturer were derived correctly. All I did was ask a question about why a certain person believes main bearing failures are due to the use of increased nominal clearance, not accumulated mileage since 2016, and then I listed the published values. I do not know whether the published values are accurate. Nothing would get accomplished in this world if we each individually have to verify the accuracy of every single thing published/manufactured.

[PaulGros]

I think you are likely missing my point. The MAHLE figure you quote is the mean clearance, so the average theorutical clearance if all parts (shaft, housing and bearings) were at average size. The other figures quoted are from a measured set, not averages. As the data isn't published on wall thickness and tolerance, their is no way of knowing if the bearings were at the lower end of allowed thickness which would show a larger clearance.

You need to see the theoretical clearance based on print wall thickness and tolerance to see what clearance is being targeted be each manufacturer. Also each manufacturer is using marginally different housing / shaft sizes to calculate which also impacts the published figures.

I've spoken to Bert at BE about this, and the fact it would allow comparison of all available parts using a standard data set.

[M3SQRD]

Originally Posted by PaulGros

I think you are likely missing my point. The MAHLE figure you quote is the mean clearance, so the average theorutical clearance if all parts (shaft, housing and bearings) were at average size. The other figures quoted are from a measured set, not averages. As the data isn't published on wall thickness and tolerance, their is no way of knowing if the bearings were at the lower end of allowed thickness which would show a larger clearance.

You need to see the theoretical clearance based on print wall thickness and tolerance to see what clearance is being targeted be each manufacturer. Also each manufacturer is using marginally different housing / shaft sizes to calculate which also impacts the published figures.

I've spoken to Bert at BE about this, and the fact it would allow comparison of all available parts using a standard data set.

I was unaware that the BE values were measured values. I, incorrectly, thought the BE values also were averaged (mean) theoretical values, not measured values. I went back thru the thread where I found the two BE values and the one Mahle value. It is clearly stated in the thread that the BE values are measured values. However, that statement was made several posts later in the thread, not in the post where the RB numbers were being compared. Thank you for setting me straight.

[PaulGros]

Originally Posted by M3SQRD

I was unaware that the BE values were measured values. I, incorrectly, thought the BE values also were averaged (mean) theoretical values, not measured values. I went back thru the thread where I found the two BE values and the one Mahle value. It is clearly stated in the thread that the BE values are measured values. However, that statement was made several posts later in the thread, not in the post where the RB numbers were being compared. Thank you for setting me straight.

No problem.

This is the problem sometimes with the available data, it's not clear if you are used to dealing with the information, so it's more difficult when you don't deal with it daily. For me, the theoretical values show what being targeted, the actual measured show how well each manufacturer is controlling production and delivering what they claim. Both have value :-)

[Assimilator1]

Originally Posted by Sneaky Pete

You could well be right, its may just be simple wear and tear.
And I guess so many owners having been duped into believing that the OEM rod bearing clearance was too tight, would be reluctant to believe a new scare under the well known scientific principle of once bitten twice shy.

Yet does it not make you wonder...when you fit rod bearings with extra clearance which allows oil to flow much more easily out of the bearings...and oil will always flow towards the point of least resistance...is there no possibility that the unintended consequence of fitting these under sized rod bearings bearings will be reduced flow through the main bearings?
.....

Increased clearance at the rod bearings will increase flow through the mains and the rod bearings (bearing in mind the variable volume pump making up for the greater oil flow out of the rod bearings).

Originally Posted by PaulGros

But only one of those is calculated from the actual print data.

As far a I am aware the BE figures are from a measured set. How do you know they were in spec to the print? As far as I am aware, BE has not published their wall thickness data or tolerance from the print. And yes, this is something I have spoken to Robert about.

.......

But doesn't hand measuring of every single shell (as BE do) before selling it negate that anyway?

[Sneaky Pete]

Originally Posted by Assimilator1

Increased clearance at the rod bearings will increase flow through the mains and the rod bearings (bearing in mind the variable volume pump making up for the greater oil flow out of the rod bearings).

My meagre understanding of fluid dynamics is that increasing flow through the rod bearings by increasing clearance will *not* increase flow through the main bearings...in fact the opposite.
This may or may not be a good analogy but:
Imagine a pressurised hose with 16 holes in it, 8 representing the rate at which oil flows out of the rod bearings and 8 for the mains.
Now if you make 8 (RB) holes bigger the oil will flow out far more quickly out of those and less so out of the other 8 (mains). The flow controlled oil pump *might* see a very small drop in flow but it will be only a part of the overall output of the Mahle pump (to the Vanos, timing chains, piston cooling, cam lubrication etc)....not as a direct proportion of the reduced flow through the main bearings.
It may not make a dramatic difference or it may in some cases be just enough to significantly reduce service life of the main bearings.
Noting that one would imagine that the engine design team went to some length to balance the flow between these two sets of bearings for maximum service life...not expecting end users to change that balance.

[PaulGros]

Originally Posted by Assimilator1

But doesn't hand measuring of every single shell (as BE do) before selling it negate that anyway?

I often see the quote about hand measuring into matched sets. But I genuinely don't understand this claim. As far as I am aware you cannot specify the wall thickness you want / require from them. The Wiki data also shows the largest variation in size for them also from all parts measured, double what some brands are achieving. So what is the hand measuring achieving?

I also don't understand why its believed hand measuring is "better". Humans make more mistakes than machines, and laser / optical measuring equipment is more accurate and consistent.

[PaulGros]

Originally Posted by Sneaky Pete

My meagre understanding of fluid dynamics is that increasing flow through the rod bearings by increasing clearance will *not* increase flow through the main bearings...in fact the opposite.
This may or may not be a good analogy but:
Imagine a pressurised hose with 16 holes in it, 8 representing the rate at which oil flows out of the rod bearings and 8 for the mains.
Now if you make 8 (RB) holes bigger the oil will flow out far more quickly out of those and less so out of the other 8 (mains). The flow controlled oil pump *might* see a very small drop in flow but it will be only a part of the overall output of the Mahle pump (to the Vanos, timing chains, piston cooling, cam lubrication etc)....not as a direct proportion of the reduced flow through the main bearings.
It may not make a dramatic difference or it may in some cases be just enough to significantly reduce service life of the main bearings.
Noting that one would imagine that the engine design team went to some length to balance the flow between these two sets of bearings for maximum service life...not expecting end users to change that balance.

The rod bearings are fed from the mains, so are "down stream". Any oil flowing to the rod bearings comes via the main bearings first.