Official S65 Rod Bearing Condition Example Thread

[Assimilator1]

Originally Posted by IamFODI

Why am I only now starting to realize the game-theoretic implications of trying to answer this question? Woof!

It's highly, highly unlikely that your rod bearings are anywhere near failure right now*. Start doing oil analysis now, at every oil change, to get a baseline for the numbers your engine produces. Then watch for deviations from the baseline. A lack of deviation doesn't mean everything's fine, but a significant deviation probably means something's up.

Around 80k miles / 120k km is when I'd start thinking about changing the rod bearings preventatively. Whenever you start thinking about that, base your decision on what the evidence is at that time. And remember to make your decision on apparent failure rates, NOT just ugly-looking pictures on the Internet.

As you mentioned, but I thought worth highlighting, oil analysis is not necessarily going to find failing bearings, so it isn't worth doing it for that purpose alone (lauz, see my sig for more info on that). It could easily give a false sense of security.

*And adding a caveat, that he at least has the latter tin bearings (which being 2011 it probably does, but it still isn't 100% certain!). And of course their have been tin bearing engines that have had bearing failure (at perhaps roughly 1/2 the rate of the lead bearing version).

If it's the lead bearings (unlikely), I'd say it is at least very likely they are critically worn.

[nick3753]

2012 120k miles. I hit an object in the road, blowing a hole in the pan, so I ran with minimal oil for maybe 30-40 seconds after impact. Looks like some damage was done though, so it's a good thing they were replaced.

[jvictormp]

Originally Posted by nick3753

2012 120k miles. I hit an object in the road, blowing a hole in the pan, so I ran with minimal oil for maybe 30-40 seconds after impact. Looks like some damage was done though, so it's a good thing they were replaced.

O man, that hurts.

How may the mains be?

[nick3753]

Originally Posted by jvictormp

O man, that hurts.

How may the mains be?

That is a good question…🤞🏻.

[jvictormp]

Originally Posted by nick3753

That is a good question…🤞🏻.

I had 20 seconds of engine running after throwing a rod (not RB related).

RBs were fine except for a center mark due to oil starvation during those 20 seconds.

I had almost all the engine apart, but did not have the time to split the block and remove the crank to see the main bearings.

If I do, I'll post pictures for you to have an idea if they suffer more or less than RBs.

[nick3753]

Originally Posted by jvictormp

I had 20 seconds of engine running after throwing a rod (not RB related).

RBs were fine except for a center mark due to oil starvation during those 20 seconds.

I had almost all the engine apart, but did not have the time to split the block and remove the crank to see the main bearings.

If I do, I'll post pictures for you to have an idea if they suffer more or less than RBs.

Thanks. I got the car back Friday (only drove it the 18 miles or so home from the shop). Start my weekly work commute, plus kid transportation to athletics (about 5-600 miles per week). 🙏🏻

[Scharbag]

Originally Posted by IamFODI

Why am I only now starting to realize the game-theoretic implications of trying to answer this question? Woof!

It's highly, highly unlikely that your rod bearings are anywhere near failure right now. Start doing oil analysis now, at every oil change, to get a baseline for the numbers your engine produces. Then watch for deviations from the baseline. A lack of deviation doesn't mean everything's fine, but a significant deviation probably means something's up.

Around 80k miles / 120k km is when I'd start thinking about changing the rod bearings preventatively. Whenever you start thinking about that, base your decision on what the evidence is at that time. And remember to make your decision on apparent failure rates, NOT just ugly-looking pictures on the Internet.

I also do not agree with this logic. Mileage is not the important factor. Clearance is.

If you have a big crank, thick shells and small big end bores, your engine will not last 80k miles.

On the other hand, if you have a small crank, thin shells and large big end bores, you may have perfectly adequate clearance for 200k+ miles.

It is all statistics and arbitrarily picking a mileage number is nonsensical.

[AndyW]

Originally Posted by Scharbag

I also do not agree with this logic. Mileage is not the important factor. Clearance is.

If you have a big crank, thick shells and small big end bores, your engine will not last 80k miles.

On the other hand, if you have a small crank, thin shells and large big end bores, you may have perfectly adequate clearance for 200k+ miles.

It is all statistics and arbitrarily picking a mileage number is nonsensical.

But given the stock crank, shells, and bores are relatively fixed for a particular car (until you go aftermarket), it seems logical that mileage is a reasonable wear tracker. I mean, you varied the initial conditions and then used mileage yourself. And, of course, there is the variable of how hard the engine is driven, which can alter the estimate significantly.

Personally, I am at 43K. I just purchased the car so I don't know it's driving history, but it seems well taken care of. I am not a hard driver bit I am still likely to do rod bearings at 50K or so simply for peace of mind and because these engines are expensive. Even if my shells look great when they come out, I will not regret the decision. This thread, with all it's varying opinions, has been very valuable to me in making that decision.

[Scharbag]

Originally Posted by AndyW

But given the stock crank, shells, and bores are relatively fixed for a particular car (until you go aftermarket), it seems logical that mileage is a reasonable wear tracker. I mean, you varied the initial conditions and then used mileage yourself. And, of course, there is the variable of how hard the engine is driven, which can alter the estimate significantly.

Personally, I am at 43K. I just purchased the car so I don't know it's driving history, but it seems well taken care of. I am not a hard driver bit I am still likely to do rod bearings at 50K or so simply for peace of mind and because these engines are expensive. Even if my shells look great when they come out, I will not regret the decision. This thread, with all it's varying opinions, has been very valuable to me in making that decision.

I disagree. There is no way to know what you have until you open the engine. There exist a statistical chance of having a very tight engine. Some have failed in less than 20k miles. Others last 200k plus. It has very little to do with driving style, care, maintenance etc. If that were the case, you would have to believe that only E9x M3 owners abuse their cars.

My bearings came out looking great at 30K KM. No regrets cause there was no way to know until I was in there. So if you believe there is an issue, just change them. If you do not, the. Don't. Your choice. But arbitrary mileage targets are just that, arbitrary.

Cheers,

[BOOF-M3]

Originally Posted by AndyW

But given the stock crank, shells, and bores are relatively fixed for a particular car (until you go aftermarket), it seems logical that mileage is a reasonable wear tracker. I mean, you varied the initial conditions and then used mileage yourself. And, of course, there is the variable of how hard the engine is driven, which can alter the estimate significantly.

Personally, I am at 43K. I just purchased the car so I don't know it's driving history, but it seems well taken care of. I am not a hard driver bit I am still likely to do rod bearings at 50K or so simply for peace of mind and because these engines are expensive. Even if my shells look great when they come out, I will not regret the decision. This thread, with all it's varying opinions, has been very valuable to me in making that decision.

My shells came out at around 110k and looked great. But shavings in the oil proved otherwise. As Scharbag said, it's your car so you will decide if and when it's time.

[Green-Eggs]

Originally Posted by AndyW

But given the stock crank, shells, and bores are relatively fixed for a particular car (until you go aftermarket), it seems logical that mileage is a reasonable wear tracker. I mean, you varied the initial conditions and then used mileage yourself. And, of course, there is the variable of how hard the engine is driven, which can alter the estimate significantly.

Personally, I am at 43K. I just purchased the car so I don't know it's driving history, but it seems well taken care of. I am not a hard driver bit I am still likely to do rod bearings at 50K or so simply for peace of mind and because these engines are expensive. Even if my shells look great when they come out, I will not regret the decision. This thread, with all it's varying opinions, has been very valuable to me in making that decision.

So let me give you some data to back it up. These are the specs for all of the factory parts:

Crank journal: 2.04640 - 2.04680
Rod big-end bore: 2.20470 - 2.20520
Shell thickness: 0.07825 - 0.07875

These are the actual specs of these parts. These parts are allowed to vary anywhere in between these values and still considered within spec. But look what happens when you mix them together.

Large crank journal, small big-end bore, thick bearing shells:
Clearance will be 0.00065 inch.
This will probably blow your motor within 10000 miles -- which has actually happened to many brand new cars. One engine blew with 1500 miles on it.

Nominal everything:
Clearance will be 0.00135 inch.
Industry standard best practices would want 0.0024 inch. This "nominal" value is approximately 1/2 of the industry best practices. If there was an argument to be made that mileage matters, it would be right about here.

Small crank journal, large big-end bore, thin bearing shells:
Clearance will be 0.00205.
Still not best practice, but definitely a lot closer. With this clearance, your engine could very likely last 200k miles.

These are actual numbers. Numbers are not opinions. The only opinions are what happens to your engine with these clearances. Even that isn't much of an opinion when there's 80 years worth of automotive journals describing the best practice bearing clearances.

And, of course, there is the variable of how hard the engine is driven, which can alter the estimate significantly.

This matters less than you think. You're forgetting, or maybe don't know, that bearings are never supposed to make contact with the journal. So driving it hard, shouldn't affect the wear of the bearing when clearance is properly sized and oil flow is sufficient. When bearings are not properly sized, then oil flow suffers as well. This is when driving hard gives you metal-to-metal contact with the bearings and journals. This is where all of the wear comes from -- too little clearance will cause that contact to wear the bearings. Sufficient clearance and this won't happen.

Here's the thread you want to read to learn more about it. Warning, it's a monster sized thread though.
https://www.m3post.com/forums/showthread.php?t=892838

[its55]

The above is why the thick 10W-60 is so important to these engines, to keep oil in those minimal clearances and also why the rev indicator on the tach must be followed.

[Helmsman]

Originally Posted by Green-Eggs

So let me give you some data to back it up. These are the specs for all of the factory parts:

Crank journal: 2.04640 - 2.04680
Rod big-end bore: 2.20470 - 2.20520
Shell thickness: 0.07825 - 0.07875

These are the actual specs of these parts. These parts are allowed to vary anywhere in between these values and still considered within spec. But look what happens when you mix them together.

Large crank journal, small big-end bore, thick bearing shells:
Clearance will be 0.00065 inch.
This will probably blow your motor within 10000 miles -- which has actually happened to many brand new cars. One engine blew with 1500 miles on it.

Nominal everything:
Clearance will be 0.00135 inch.
Industry standard best practices would want 0.0024 inch. This "nominal" value is approximately 1/2 of the industry best practices. If there was an argument to be made that mileage matters, it would be right about here.

Small crank journal, large big-end bore, thin bearing shells:
Clearance will be 0.00205.
Still not best practice, but definitely a lot closer. With this clearance, your engine could very likely last 200k miles.

These are actual numbers. Numbers are not opinions. The only opinions are what happens to your engine with these clearances. Even that isn't much of an opinion when there's 80 years worth of automotive journals describing the best practice bearing clearances.



This matters less than you think. You're forgetting, or maybe don't know, that bearings are never supposed to make contact with the journal. So driving it hard, shouldn't affect the wear of the bearing when clearance is properly sized and oil flow is sufficient. When bearings are not properly sized, then oil flow suffers as well. This is when driving hard gives you metal-to-metal contact with the bearings and journals. This is where all of the wear comes from -- too little clearance will cause that contact to wear the bearings. Sufficient clearance and this won't happen.

Here's the thread you want to read to learn more about it. Warning, it's a monster sized thread though.
https://www.m3post.com/forums/showthread.php?t=892838

The spec gives a 0.00065 - 0.00205 spread, which means there are very small numbers in the extreme ends, as majority ends up around nominal. Hence the after all small number of blown motors due to tight rod shells.

0.00135 inch nominal clearance clearly takes the shells over many miles even if a bit tight, hence basically every single shells coming out has some level of wear, while not spun.

Replaced my RBs with extended clearance so I'm not suggesting that is a bad Idea. Just want us to avoid to believe majority of OEM shells is 0.00065 type tight and will blow.

[Scharbag]

Originally Posted by its55

The above is why the thick 10W-60 is so important to these engines, to keep oil in those minimal clearances and also why the rev indicator on the tach must be followed.

No no no. No no. No.

Thick is bad when clearances are tight. It is all about flow.

[Scharbag]

Originally Posted by Helmsman

The spec gives a 0.00065 - 0.00205 spread, which means there are very small numbers in the extreme ends, as majority ends up around nominal. Hence the after all small number of blown motors due to tight rod shells.

0.00135 inch nominal clearance clearly takes the shells over many miles even if a bit tight, hence basically every single shells coming out has some level of wear, while not spun.

Replaced my RBs with extended clearance so I'm not suggesting that is a bad Idea. Just want us to avoid to believe majority of OEM shells is 0.00065 type tight and will blow.

It is never implied that the majority are at the super tight end. Problem is, you don't know and there is no way to find out. Roll of the dice.

I was unwilling to take that risk. So I changed mine early. I likely did not meet to. Oh well. Now I know I am GTG.

[Green-Eggs]

Originally Posted by Helmsman

The spec gives a 0.00065 - 0.00205 spread, which means there are very small numbers in the extreme ends, as majority ends up around nominal. Hence the after all small number of blown motors due to tight rod shells.

I wonder if this comment would change if you knew that every brand new factory rod we've ever measured was exactly 2.2047 on the big end. Now, re-run these theoretical clearance numbers and watch what happens to nominal clearance; it becomes even more extreme and tighter.

[Green-Eggs]

Originally Posted by its55

The above is why the thick 10W-60 is so important to these engines, to keep oil in those minimal clearances and also why the rev indicator on the tach must be followed.

It's exactly the opposite of this. The oil needs to flow to create a wedge where the bearing never touches the journal. If the oil is too thick, then it can't do this effectively. This has been discussed and analyzed in the big bearing wiki thread, along with industry white papers which state that if you have thinner clearances, then you need thinner oils...not thicker oils like 10W60.

[nycplumber]

Ironic since bmw changed to 10w60 after all the bearing issues on the s54

[Green-Eggs]

Originally Posted by nycplumber

Ironic since bmw changed to 10w60 after all the bearing issues on the s54

For S65, they were also paid by Castrol and offered indemnification for blown motors. All covered in the bearing wiki thread.

Didn't S54 spec 10W60 oil as well? A quick search looks like it.

[DrFerry]

Originally Posted by Green-Eggs

For S65, they were also paid by Castrol and offered indemnification for blown motors. All covered in the bearing wiki thread.

Didn't S54 spec 10W60 oil as well? A quick search looks like it.

Can you address if 10W60 should always be used with the S65 BE bearings and if so why? Thanks in advance.
.

[Green-Eggs]

Originally Posted by DrFerry

Can you address if 10W60 should always be used with the S65 BE bearings and if so why? Thanks in advance.
.

With industry best practice clearances, the 10W60 will be fine. When BE was developed and tested, only 10W60 was tested with their computerized oil flow meter and analysis testing. Testing different oil viscosities would take about 1-year each, and require reprofiling/reprogramming the oil flow meter for each viscosity. So basically, it's not worth the time and energy.

Oil flow analysis:
http://wiki.rcollins.org/core/index...._Flow_Analysis

[AndyW]

Originally Posted by Green-Eggs

So let me give you some data to back it up. These are the specs for all of the factory parts:

Crank journal: 2.04640 - 2.04680
Rod big-end bore: 2.20470 - 2.20520
Shell thickness: 0.07825 - 0.07875

These are the actual specs of these parts. These parts are allowed to vary anywhere in between these values and still considered within spec. But look what happens when you mix them together.

Large crank journal, small big-end bore, thick bearing shells:
Clearance will be 0.00065 inch.
This will probably blow your motor within 10000 miles -- which has actually happened to many brand new cars. One engine blew with 1500 miles on it.

Nominal everything:
Clearance will be 0.00135 inch.
Industry standard best practices would want 0.0024 inch. This "nominal" value is approximately 1/2 of the industry best practices. If there was an argument to be made that mileage matters, it would be right about here.

Small crank journal, large big-end bore, thin bearing shells:
Clearance will be 0.00205.
Still not best practice, but definitely a lot closer. With this clearance, your engine could very likely last 200k miles.

These are actual numbers. Numbers are not opinions. The only opinions are what happens to your engine with these clearances. Even that isn't much of an opinion when there's 80 years worth of automotive journals describing the best practice bearing clearances.



This matters less than you think. You're forgetting, or maybe don't know, that bearings are never supposed to make contact with the journal. So driving it hard, shouldn't affect the wear of the bearing when clearance is properly sized and oil flow is sufficient. When bearings are not properly sized, then oil flow suffers as well. This is when driving hard gives you metal-to-metal contact with the bearings and journals. This is where all of the wear comes from -- too little clearance will cause that contact to wear the bearings. Sufficient clearance and this won't happen.

Here's the thread you want to read to learn more about it. Warning, it's a monster sized thread though.
https://www.m3post.com/forums/showthread.php?t=892838

Thx. This is very helpful.