Consensus on rod bearings?

Scrippy wrote

The motors you mention either have lower redlines or half the rotating mass. I hear ya though.

Audi V10 5.2L - 8700RPM red line - ~500ml per hole
Honda I4 AP1 - 8900RPM red line - ~500ml per hole
Porsche F6 GT3 - 9000RPM red line - ~500ml per hole
S65 - 8400RPM red line - ~500ml per hole

The mass of the rotating assembly has very little to do compared to the piston/rod mass and velocity when considering rod bearing forces. And technically, the rotating mass includes the crank, flywheel and all other connected components.

Only the S65 seems to eat bearings...

I plan on replacing mine at 175k. At that point I'll also be rebuilding VANOS, and a couple other OE items prior to supercharging. Obviously they can go at any time, like any other part in the car, but I'd be crazy to add more hp without making everything else as robust as possible.

On my 2008 M3, I replaced rod bearings at 64,000 miles with BE bearings. The originals definitely had some pronounced signs of wear so it was a good call to do the service. I later purchased a 2011 M3 and had the bearings replaced at 69,000 miles. The updated 2011 bearings still looked pretty good with minimal signs of wear and probably would have lasted longer. Replacing the rod bearings is like buying insurance, and I am glad to have done it. My shop does this service regularly M3s and M5s and the pricing was fair. A couple years ago, they had a customer scheduled to have them replaced, but he spun a bearing and nuked the engine while joy riding the weekend before taking it in for service. You just never know!

amrazM wrote

how are these questions still being asked

New school owners.

Damn you rod bearings!! Lol
Here’s my thoughts, the S65 is a high performance and high compression engine. They are all manufactured the same. However every single engine out there is run and maintained differently. Some stick to the bmw recommended engine oil and change intervals. Some run different oils and change oil more frequently then what Bmw recommends. Also some owners crank and go and others let the engine warm up before they drive off. There are so many variables that can account for whether a bearing will fail or not! I do recommend changing rod bearings at 100k. I’m not sold on failure due to a clearance issue, seems if it was a clearance issue every engine would fail early on. I feel it has more to do with the initial break in, how the car is maintained, how it is driven, etc. However since the S65 is such a performace engine, high compression and high rpm, I strongly recommend changing rod bearings at 100k.

Get lit wrote

Damn you rod bearings!! Lol
Here's my thoughts, the S65 is a high performance and high compression engine. They are all manufactured the same. However every single engine out there is run and maintained differently. Some stick to the bmw recommended engine oil and change intervals. Some run different oils and change oil more frequently then what Bmw recommends. Also some owners crank and go and others let the engine warm up before they drive off. There are so many variables that can account for whether a bearing will fail or not! I do recommend changing rod bearings at 100k. I'm not sold on failure due to a clearance issue, seems if it was a clearance issue every engine would fail early on. I feel it has more to do with the initial break in, how the car is maintained, how it is driven, etc. However since the S65 is such a performace engine, high compression and high rpm, I strongly recommend changing rod bearings at 100k.

They are not all manufactured the same. No where close.

Your theory has been debunked over and over and over.

These discussions are becoming repetitive and boring.

Consensus? The question that every new owner asks. No, there isn’t one. And no there is no simple explanation for excess rod bearing wear or failure. Read and make your decision. My advice is to think of preventative maintenance as like insurance — you are paying to reduce a risk. If you don’t believe there is a risk and can pay $8k for a used motor or $12k installed ($18k if using a dealership), then don’t worry.

If you're paying $25-35k for a decade old car because it stirs your soul, what's an extra $2500 for some peace of mind? First thing I did when I bought mine with 60k miles. Zero regrets.

I will be the ultimate guinea pig for the forum. Even I come into a significant amount of money, hit 100k on the odometer or get a ridiculously high reading. Until then, its the German lottery for me.

Actually, probably 3/4 of owners are the guinea pigs with original rod bearings. They have been doing well since the odds of failure have been low so far. Of the perhaps 1/4 who changed bearings, most were done preventatively and not because of failure. Failures are probably 5% of cars at most, though there is no solid data because dealers don’t report and a minority of owners are members here.

blastpanel wrote

On my 2008 M3, I replaced rod bearings at 64,000 miles with BE bearings. The originals definitely had some pronounced signs of wear so it was a good call to do the service. I later purchased a 2011 M3 and had the bearings replaced at 69,000 miles. The updated 2011 bearings still looked pretty good with minimal signs of wear and probably would have lasted longer. Replacing the rod bearings is like buying insurance, and I am glad to have done it. My shop does this service regularly M3s and M5s and the pricing was fair. A couple years ago, they had a customer scheduled to have them replaced, but he spun a bearing and nuked the engine while joy riding the weekend before taking it in for service. You just never know!

What shop do you use? Looking to get mine done after the first of the year.

Eurotechnik in Hendersonville. Great shop! https://eurotechnikauto.com/

Scharbag wrote

They are not all manufactured the same. No where close.

Your theory has been debunked over and over and over.

These discussions are becoming repetitive and boring.

So tell me.... why do rod bearings fail? Why do main bearings fail. I never stated a reason in my post about failure of rod bearings. As I stated they have many variables that can account for failure. And every bearing produced wether aftermarket or Oem are within the production specs of that manufacture. Personally I never stressed about bearing failure. I never changed them in my e90. The next owner changed them at 115k just for peace of mind after recommending him to do so. And the old bearings were not in bad condition. All wear was light even across the bearing surfaces. I really don’t stress about engine failure. If it fails, I’ll put a new engine in!

And if these discussion are becoming repetitive and boring why the hell are you still reading and commenting on them??

Get lit wrote

So tell me.... why do rod bearings fail? Why do main bearings fail. I never stated a reason in my post about failure of rod bearings. As I stated they have many variables that can account for failure. And every bearing produced wether aftermarket or Oem are within the production specs of that manufacture. Personally I never stressed about bearing failure. I never changed them in my e90. The next owner changed them at 115k just for peace of mind after recommending him to do so. And the old bearings were not in bad condition. All wear was light even across the bearing surfaces. I really don’t stress about engine failure. If it fails, I’ll put a new engine in!

And if these discussion are becoming repetitive and boring why the hell are you still reading and commenting on them??

I read and comment to ensure that others who read these forums see information instead of opinion.

Clevite has a very nice description of why hydrodynamic bearings fail here. I suggest you read it.

You say "all S65 engines are made the same." - This is simply untrue. Nothing is ever "made the same." There will always be manufacturing tolerances. If you choose to not measure before assembly (which BMW did not do for cranks, rods and rod bearings on the S65/S85), then you will have tolerance stack. This is simple statistics and the primary reason that many manufactures use different sized rod bearing shells when building engines (BMW did not do this on the S65).

You say "...every bearing produced wether aftermarket or Oem are within the production specs of that manufacture." - while this may be true most of the time, QA/QC is never perfect (BE throws out some shells due to being out of spec while hand matching sets to remove this variable) AND you fail to mention what those tolerances are (it is cheaper to be sloppy, harder to be precise - law of diminishing returns). Also, you fail to mention and/or understand that even if 100% of the parts are within the manufacturers tolerance, there will still be tolerance stack when you combine parts (big crank, small big-end bore and thick shells have been shown to allow for only 0.00029"/" of clearance with 088/089 bearings - eek!). This is the real issue. Not the quality of each part, but the overall quality of the final assembly. This is the root issue with the S65 rod bearings.

As for the single data point from your E90 - you got lucky and had an engine with tolerance stack that allowed for adequate oil clearance. My engine was the same. Others are not so lucky. It is all just statistics and some people are dealt a bad hand.

And I am happy for you that you can afford a $12,000USD engine swap if you need to. Many owners, including myself, would be challenged to spend that much money to fix a used car. Each person will have to make their own informed choice.

Happy motoring.

pbonsalb wrote

Actually, probably 3/4 of owners are the guinea pigs with original rod bearings. They have been doing well since the odds of failure have been low so far. Of the perhaps 1/4 who changed bearings, most were done preventatively and not because of failure. Failures are probably 5% of cars at most, though there is no solid data because dealers don’t report and a minority of owners are members here.

Spot on ! Well said mate !

Get lit wrote

Some stick to the bmw recommended engine oil and change intervals. Some run different oils and change oil more frequently then what Bmw recommends. Also some owners crank and go and others let the engine warm up before they drive off. There are so many variables that can account for whether a bearing will fail or not!

Yea is what every new owner seems to think.

Most of us owners that have been around when these were still being produced know better. Go read some of the early failures here, start with the very first page and keep going:https://www.m3post.com/forums/showthread.php?t=786615

tdott wrote

Yea is what every new owner seems to think.

Most of us owners that have been around when these were still being produced know better. Go read some of the early failures here, start with the very first page and keep going:https://www.m3post.com/forums/showthread.php?t=786615

I’ve been around for all the rod bearing post. Even been around when the class action lawsuits started! I’m sorry but I’m not sold on any particular opinion on why or reason rod bearings have failed. Like I said, it Is way too many variables that can account for rod bearing failure in an engine.

Bottom line here is everyone has their opinion about rod bearings, if some of the new owners of the e9x m3 are buying these cars now and are worried about the rod bearings then go ahead and change them out. It’s always good piece of mind! Also there are tons of other maintenance items that should also be addressed when these cars get up in mileage along with rod bearings.

Get lit wrote

tdott wrote

Yea is what every new owner seems to think.

Most of us owners that have been around when these were still being produced know better. Go read some of the early failures here, start with the very first page and keep going:https://www.m3post.com/forums/showthread.php?t=786615

I’ve been around for all the rod bearing post. Even been around when the class action lawsuits started! I’m sorry but I’m not sold on any particular opinion on why or reason rod bearings have failed. Like I said, it Is way too many variables that can account for rod bearing failure in an engine.

Bottom line here is everyone has their opinion about rod bearings, if some of the new owners of the e9x m3 are buying these cars now and are worried about the rod bearings then go ahead and change them out. It’s always good piece of mind! Also there are tons of other maintenance items that should also be addressed when these cars get up in mileage along with rod bearings.

Which other variables are you discussing?

Replaced at 100,000km for my 6MT(2007 euro, I believe I am around 700th in production).. oil changes done every 5,000km since new.

ALL bearings showed copper layers with one of the upper bearings in cylinder 1 severely worn. I wouldn't leave it up to chance; change them and be done with it.

Variables, any engine the break in is very important (except for certain race engines, they start their life at redline!), maintenance schedules, climate and conditions it’s operated in, how the engine is operated, modified/upgraded performance parts Added, Highway or city operation, quality of fuel that is used, oils that are used, the list can go on.

I’m not trying to get into a pissing match with you. And please don’t read my post as if I’m being a dick. I’m just stating my thoughts on this subject. I’m a car guy, love discussing car stuff and sharing my thoughts and also listening to others input and thoughts! If you want to talk more about this subject send me a pm!

Get lit wrote

Variables, any engine the break in is very important (except for certain race engines, they start their life at redline!), maintenance schedules, climate and conditions it's operated in, how the engine is operated, modified/upgraded performance parts Added, Highway or city operation, quality of fuel that is used, oils that are used, the list can go on.

I'm not trying to get into a pissing match with you. And please don't read my post as if I'm being a dick. I'm just stating my thoughts on this subject. I'm a car guy, love discussing car stuff and sharing my thoughts and also listening to others input and thoughts! If you want to talk more about this subject send me a pm!

I do not feel you are being a dick at all - I like good discussions. All good.

As for the variables you mentioned:

Break-in - bearings do not break in. Also, some professionals suggest engine break-in should be done quickly under load. I have raced a lot of Honda products and every one of my re-built junk yard B16 and B18 engines have been broken in on the track. They all ran strong and lived life bouncing off the limiter. Hell, our latest B18 has 4 24 hour races (~9,000KM) under its belt with 170TKM on the junk yard engine with new rings and bearings (did not touch the head at all).

Maintenance - I agree, proper maintenance is important to every reciprocating engine. That said, if maintenance is such a big deal, then every high revving engine should share the S65/S85 penchant for bearing wear. Unless BMW M owners are just bad at maintenance - which does not seem to be the case typically as we are neurotic car freaks. And the typical issues that I have seen from LCI is sludge buildup in the heads, not bearing damage.

Climate/conditions - Engine oils today can run 250F+ no problems. Also, modern synthetics can still be pumped when very cold. That said, -40 and 10W60 freaks me out (never did that to my M). Why do we not see similar issues with Audi, Porsche, Honda etc.?

Operation - All reciprocating engines share certain fundamentals. Audi, Porsche, Honda, Ferrari, Lamborghini, Bugatti etc. all have to follow the same rules of physics. If high RPM use is detrimental to all high HP NA engines, then we should see similar rod bearing failure rates in other brands with similar HP/L NA engines. (This statement assumes that the engine is not abused, which is different than being driven at high RPM.)

Fuel - this has almost nothing to do with rod bearing failure. Yes, detonation can cause excessive loads - but - this raises the question: do only S65 and S85 owners use crappy fuel in their high performance engines? Also, the MSS60 would throw some codes if the detonation was really that bad.

Oil - Any good 0W40 or thicker synthetic has been shown to work just fine in the S65 (not sure how the S85 VANOS reacts to thinner oils). Modern synthetic oils are all very very stout and we all typically change the oil WAY more often than needed.

Mods - The S65 can easily run 600+HP and 400+ftlb of torque with a blower. Yes, too much load will eventually break something - but the S65 is pretty stout. Most E9x M3s are not boosted. Given the S65 can accept boost without immediate blowup, this leads me to posit that there exists no NA mods for the S65 that will cause undue stress on the rotating assembly.

Anywhoo, each owner can make their own choice. I am happy I changed mine even though I got lucky and seemed to have adequate clearances.

Happy motoring and keep the revs up. I know I do. Perhaps that is why I average 11MPG... :P

Scharbag wrote

Get lit wrote

Variables, any engine the break in is very important (except for certain race engines, they start their life at redline!), maintenance schedules, climate and conditions it's operated in, how the engine is operated, modified/upgraded performance parts Added, Highway or city operation, quality of fuel that is used, oils that are used, the list can go on.

I'm not trying to get into a pissing match with you. And please don't read my post as if I'm being a dick. I'm just stating my thoughts on this subject. I'm a car guy, love discussing car stuff and sharing my thoughts and also listening to others input and thoughts! If you want to talk more about this subject send me a pm!

I do not feel you are being a dick at all - I like good discussions. All good.

As for the variables you mentioned:

Break-in - bearings do not break in. Also, some professionals suggest engine break-in should be done quickly under load. I have raced a lot of Honda products and every one of my re-built junk yard B16 and B18 engines have been broken in on the track. They all ran strong and lived life bouncing off the limiter. Hell, our latest B18 has 4 24 hour races (~9,000KM) under its belt with 170TKM on the junk yard engine with new rings and bearings (did not touch the head at all).

Maintenance - I agree, proper maintenance is important to every reciprocating engine. That said, if maintenance is such a big deal, then every high revving engine should share the S65/S85 penchant for bearing wear. Unless BMW M owners are just bad at maintenance - which does not seem to be the case typically as we are neurotic car freaks. And the typical issues that I have seen from LCI is sludge buildup in the heads, not bearing damage.

Climate/conditions - Engine oils today can run 250F+ no problems. Also, modern synthetics can still be pumped when very cold. That said, -40 and 10W60 freaks me out (never did that to my M). Why do we not see similar issues with Audi, Porsche, Honda etc.?

Operation - All reciprocating engines share certain fundamentals. Audi, Porsche, Honda, Ferrari, Lamborghini, Bugatti etc. all have to follow the same rules of physics. If high RPM use is detrimental to all high HP NA engines, then we should see similar rod bearing failure rates in other brands with similar HP/L NA engines. (This statement assumes that the engine is not abused, which is different than being driven at high RPM.)

Fuel - this has almost nothing to do with rod bearing failure. Yes, detonation can cause excessive loads - but - this raises the question: do only S65 and S85 owners use crappy fuel in their high performance engines? Also, the MSS60 would throw some codes if the detonation was really that bad.

Oil - Any good 0W40 or thicker synthetic has been shown to work just fine in the S65 (not sure how the S85 VANOS reacts to thinner oils). Modern synthetic oils are all very very stout and we all typically change the oil WAY more often than needed.

Mods - The S65 can easily run 600+HP and 400+ftlb of torque with a blower. Yes, too much load will eventually break something - but the S65 is pretty stout. Most E9x M3s are not boosted. Given the S65 can accept boost without immediate blowup, this leads me to posit that there exists no NA mods for the S65 that will cause undue stress on the rotating assembly.

Anywhoo, each owner can make their own choice. I am happy I changed mine even though I got lucky and seemed to have adequate clearances.

Happy motoring and keep the revs up. I know I do. Perhaps that is why I average 11MPG... :P

Thank you for taking the time to explain all of this. It seems like people have a hard time trying to wrap their minds around complex issues like sporadic rod bearing wear/failure.

Some of us understand the statistics at play - that there's a bell-shaped curve that all S65s exist under where one end of the curve is bearing failure and the other end are nice looking high-mileage bearings, and a continuous spectrum in between. Engineering of the S65 dictates the chances any S65 will land at any particular point under the curve.

With that said other people have a harder time thinking about the complexity of population statistics and will just say there's too many variables to be able to say anything either way. Scharbag breaks those variables down nicely and makes it clear that these variables are just background noise in the life of any particular S65 in operation. The risk factors for S65 RB wear/failure are distinctly different from the background noise. I don't think we fully understand the risk factors, but we do have samples that let us know something is not right. And just because you cannot yet definitively identify the cause does not mean there's nothing going on.

So while we are still trying to understand the mechanism underlying S65 RB wear/failure, which may may never fully understand, we do know something is not right. What you choose to do with that info is up to you.