Official S65 Bearing Specification/Clearance Wiki

[Sti2e92sedan]

So I've been following this thread for the past couple weeks ago but haven't replied till now.

My 08 e90 engine was blown last May of this year and has been in the shop till this day. Im at 68k miles only mod was x pipe and exhaust. I daily drove my car added about 25k miles in one year never tracked it always keep rpms low and maintained by dealer.

It's been in the shop this long due to swapping the s65 with the s85 engine. Total retrofit project! Follow my thread for updates. http://www.m3post.com/forums/showthr...Blown+S85+swap


Anyways since I've been reading the bearing issues on these engines it concerns me a lot as I'd like to keep my car for quite sometime. Now that I've already needed to replace the engine, I don't want to spend more to fix this issue. I've been following the posts about thinner oil maybe the solution. Would 0w-40 help? Maybe it's the cold start issue I'm thinking of due to driving a lot during the day and let it stay overnight and start up early morning

[regular guy]

Originally Posted by Yellow Snow

His input would be very welcome. However, the design of the S14 was more old skool, so if he could consult with the newer thinking designers it would be great to learn their take on the S65 bearing design.

He was in his 20's out of college when he started, and early 30's when he left. I think it would be a mistake to assume his career peaked at BMW. He's much better known for what he's done outside of BMW than what he did inside. Let's just leave it at that for now.

Sure it was old school back then. It was back at a time when engineers didn't need to worry about lasting 15000 miles between oil changes and they didn't try to make a name for themselves by reinventing the bearing wheel and deviating what's always worked for the past 80 years.

[regular guy]

Originally Posted by JEllis

From what I understand even the S14 suffered from rod bearing issues. Also, from what I have read most S14s are in "zone" for a rebuild between 100K-140K miles... unless you don't mind oil consumption. I am not saying this to discredit the engineer that produced the S14, because its a fantastic motorsport engine. I say this because I have often thought that most high performance motorsport engines tend have shorter lives than your average commuter motor. I will be interested to hear what your expert has to say on the issue. I wonder if he will be blunt with you.

As an aside I found this interesting article on Pelican Parts.

http://www.pelicanparts.com/bmw/tech...d-Bearings.htm

I hadn't heard that about the S14 rod bearings. But I'm not terribly familiar with the motor either. Burning oil isn't related to rod bearings. Burning oil is rings and piston-to-wall clearance. Back at that time, piston-to-wall clearance had to be 4x what it is today. The S14 piston-to-wall clearance is spec'd at 0.00180" with a maximum tolerance of 0.00600" before the piston must be replaced. The S65 piston-to-wall clearance is spec'd at 0.00000" with a maximum tolerance of 0.00200" before the piston must be replaced. A 1980's engine that can last 100000-140000 miles would be today's equivalent of lasting 250000-300000 miles. I'm still going to stick my neck out and say only a very small percentage of S65's will ever see 140000 miles.

Regarding my former collegue and former BMW engine designer. I'm not sure how many people would be swayed by his opinion. If I called him for business and then dropped the question casually, he'd probably answer. But that's the catch, I don't have a business reason to call him right now. I'll see if I can think of something over the next few days.

[regular guy]

OK, so I dug up all of the clearance specs for every BMW ///M engine ever made. I still don't have official S65 clearances specs, so these specs came from my measurements. Again, the S65 sticks out like a sore thumb as having the worst clearance-to-journal size ratio in the list. I also added the oil weight for the engine. This is kind of Voodoo because you have to read it from a chart and there are footnotes for things like when the oil changed type, etc. So I did the best I could, but if there's an error please be gentle.

BMW ///M Engines (Main Bearings)
Sorted by Model

Model	Engine	Max RPM	Oil	Min(mm)	Avg(mm)	Max(mm)	Min(SAE)	Avg(SAE)	Max(SAE)	Size(mm)	Ratio(mm)	Size(SAE)	Ratio(SAE)	RPM-Clr Ratio
E28 M5	S38B35 (Main)	6900	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	59.987	0.0006	2.362	0.00055	1254
E30 M3	S14 (Main)	6900	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	54.987	0.0006	2.165	0.00060	1150
E30 M3	S14 (Main)	6900	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	55.000	0.0009	2.165	0.00091	759
E34 M5	S38B35 (Main)	6900	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	59.987	0.0006	2.362	0.00055	1254
E34 M5	S38B35 (Main)	6900	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	60.000	0.0008	2.362	0.00083	828
E34 M5	S38B36 (Main)	7200	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	59.987	0.0006	2.362	0.00055	1309
E34 M5	S38B36 (Main)	7200	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	60.000	0.0008	2.362	0.00083	864
E36 M3	S50B30 (Main)	7280	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	59.964	0.0006	2.361	0.00055	1323
E36 M3	S50B32 (Main)	7600	0W30 to 5W40	0.020	0.033	0.046	0.00079	0.00130	0.00181	59.964	0.0006	2.361	0.00055	1381
E36 M3 Vert	S52 (Main)	6800	0W30 to 5W40	0.020	0.039	0.058	0.00079	0.00154	0.00228	59.987	0.0007	2.362	0.00065	1046
E39 M5	S62 (Main)	7000	10W60 (-02/2000)	0.025	0.038	0.050	0.00098	0.00148	0.00197	69.964	0.0005	2.754	0.00054	1306
E39 M5	S62 (Main)	7000	5W30 (+03/2000)	0.025	0.038	0.050	0.00098	0.00148	0.00197	69.964	0.0005	2.754	0.00054	1306
E45 M5	S38B38 (Main)	7200	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	60.000	0.0008	2.362	0.00083	864
E46 M3	S54 (Main)	8000	10W60 (-02/2000)	0.019	0.036	0.052	0.00075	0.00140	0.00205	59.964	0.0006	2.361	0.00059	1351
E46 M3	S54 (Main)	8000	5W30 (+03/2000)	0.019	0.036	0.052	0.00075	0.00140	0.00205	59.964	0.0006	2.361	0.00059	1351
E60 M5	S85 (Main)	8250	10W60	0.029	0.037	0.046	0.00115	0.00144	0.00180	59.984	0.0006	2.362	0.00061	1353
E92 M3	S65 (Main)	8400	10W60	0.029	0.037	0.046	0.00115	0.00144	0.00180	59.984	0.0006	2.362	0.00061	1378
Ferrari 328 GTS	3.2L (Main)	7700	10W40	0.013	0.032	0.051	0.00051	0.00126	0.00201	62.986	0.0005	2.480	0.00051	1516

BMW ///M Engines (Rod Bearings)
Sorted by Model

Model	Engine	Max RPM	Oil	Min(mm)	Avg(mm)	Max(mm)	Min(SAE)	Avg(SAE)	Max(SAE)	Size(mm)	Ratio(mm)	Size(SAE)	Ratio(SAE)	RPM-Clr Ratio
E28 M5	S38B35 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E30 M3	S14 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E34 M5	S38B35 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E34 M5	S38B36 (Rod)	7200	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	921
E34 M5	S38B38 (Rod)	7200	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	706
E36 M3	S50B30 (Rod)	7280	0W30 to 5W40	0.028	0.049	0.070	0.00110	0.00193	0.00276	50.000	0.0010	1.969	0.00098	743
E36 M3	S50B32 (Rod)	7600	0W30 to 5W40	0.026	0.047	0.068	0.00102	0.00185	0.00268	49.000	0.0010	1.929	0.00096	792
E36 M3 Vert	S52 (Rod)	6800	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	45.000	0.0008	1.772	0.00083	816
E39 M5	S62 (Rod)	7000	10W60 (-02/2000)	0.029	0.048	0.067	0.00114	0.00189	0.00264	49.000	0.0010	1.929	0.00098	715
E39 M5	S62 (Rod)	7000	5W30 (+03/2000)	0.029	0.048	0.067	0.00114	0.00189	0.00264	49.000	0.0010	1.929	0.00098	715
E46 M3	S54 (Rod)	8000	10W60 (-02/2000)	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	784
E46 M3	S54 (Rod)	8000	5W30 (+03/2000)	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	784
E60 M5	S85 (Rod)	8250	10W60	0.028	0.033	0.048	0.00110	0.00128	0.00189	51.984	0.0006	2.047	0.00063	1319
E92 M3	S65 (Rod)	8400	10W60	0.028	0.033	0.048	0.00110	0.00128	0.00189	51.984	0.0006	2.047	0.00063	1343
Ferrari 328 GTS	3.2L (Rod)	7700	10W40	0.046	0.068	0.089	0.00181	0.00266	0.00350	43.628	0.0015	1.718	0.00155	498

BMW ///M Engines (Main Bearings)
Sorted by Clearance-to-Journal Ratio

Model	Engine	Max RPM	Oil	Min(mm)	Avg(mm)	Max(mm)	Min(SAE)	Avg(SAE)	Max(SAE)	Size(mm)	Ratio(mm)	Size(SAE)	Ratio(SAE)	RPM-Clr Ratio
Ferrari 328 GTS	3.2L (Rod)	7700	10W40	0.046	0.068	0.089	0.00181	0.00266	0.00350	43.628	0.0015	1.718	0.00155	498
E34 M5	S38B38 (Rod)	7200	0W30 to 5W40	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	706
E46 M3	S54 (Rod)	8000	10W60 (-02/2000)	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	784
E46 M3	S54 (Rod)	8000	5W30 (+03/2000)	0.030	0.050	0.070	0.00118	0.00197	0.00276	49.000	0.0010	1.929	0.00102	784
E36 M3	S50B30 (Rod)	7280	0W30 to 5W40	0.028	0.049	0.070	0.00110	0.00193	0.00276	50.000	0.0010	1.969	0.00098	743
E39 M5	S62 (Rod)	7000	10W60 (-02/2000)	0.029	0.048	0.067	0.00114	0.00189	0.00264	49.000	0.0010	1.929	0.00098	715
E39 M5	S62 (Rod)	7000	5W30 (+03/2000)	0.029	0.048	0.067	0.00114	0.00189	0.00264	49.000	0.0010	1.929	0.00098	715
E36 M3	S50B32 (Rod)	7600	0W30 to 5W40	0.026	0.047	0.068	0.00102	0.00185	0.00268	49.000	0.0010	1.929	0.00096	792
E36 M3 Vert	S52 (Rod)	6800	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	45.000	0.0008	1.772	0.00083	816
E28 M5	S38B35 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E30 M3	S14 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E34 M5	S38B35 (Rod)	6900	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	883
E34 M5	S38B36 (Rod)	7200	0W30 to 5W40	0.020	0.038	0.055	0.00079	0.00148	0.00217	47.983	0.0008	1.889	0.00078	921
E60 M5	S85 (Rod)	8250	10W60	0.028	0.033	0.048	0.00110	0.00128	0.00189	51.984	0.0006	2.047	0.00063	1319
E92 M3	S65 (Rod)	8400	10W60	0.028	0.033	0.048	0.00110	0.00128	0.00189	51.984	0.0006	2.047	0.00063	1343

[JEllis]

The S65/85 does look to the have the tightest clearances but would you also conclude that the majority of the engines listed show tight clearances as well? If so, your chart shows two decades of tight clearances and 9 different engine programs and assembly lines.

[regular guy]

Originally Posted by Yellow Snow

We still don't know for sure that there is anything wrong with the clearance. The M designers obviously built in the clearances and eccentricity for a reason. I think it's fair to say they have more technical knowledge and R&D support than anyone on the forum.

Is the extra eccentricity of the bearings part of their deliberate design criteria? Can you do a comparison to a regular BMW shell

Grinding a thou off the journals really does seem like a crazy idea when the facts aren't proven.

There are three things that you know for a fact:

1. There is a long standing clearance-to-journal ratio best practice rule that factory and racing engine builders alike have followed for 50+ years. This best practice clearance ratio is well documented in dozens of web sites, and recommended by Clevite, the maker of the S65 engine bearings. The S65 engine cuts that clearance ratio in half.
2. The bearing wear patterns we're seeing all match the Clevite online/interactive bearing failure diagnosis web site, example #12 "Oil Starvation / Marginal Oil Film Thickness." The main cause mentioned by Clevite for this type of failure is "too little bearing oil clearance."
3. There is also a long standing rod side clearance best practice rule that factory and racing engine builders alike have followed for quite some time. Best practice clearance ratio is well documented in dozens of web sites. The S65 engine cuts that clearance ratio by two orders of magnitude.

[regular guy]

Originally Posted by JEllis

The S65/85 does look to the have the tightest clearances but would you also conclude that the majority of the engines listed show tight clearances as well? If so, your chart shows two decades of tight clearances and 9 different engine programs and assembly lines.

I'm not going to say the Clevite journal clearance white paper is the end-all or definitive source. But I will say the only engine on this list that violates that spec, and 80 years of engine design best practice is the S65. The S65 clearance ratio is 16% smaller than the minimum value recommended by that spec. Whereas the next closest, E34 M5 is 4% larger than the minimum value recommended by that spec.

[regular guy]

Originally Posted by regular guy

OK, so I dug up all of the clearance specs for every BMW ///M engine ever made. I still don't have official S65 clearances specs, so these specs came from my measurements. Again, the S65 sticks out like a sore thumb as having the worst clearance-to-journal size ratio in the list. I also added the oil weight for the engine. This is kind of Voodoo because you have to read it from a chart and there are footnotes for things like when the oil changed type, etc. So I did the best I could, but if there's an error please be gentle.

BMW ///M Engines (Main Bearings)
Sorted by Model


BMW ///M Engines (Rod Bearings)
Sorted by Model


BMW ///M Engines (Main Bearings)
Sorted by Clearance-to-Journal Ratio

And take notice the E46 with nearly twice the journal clearance of the S65 started life with 10W60 oil, then changed to 5W30.

[JEllis]

Originally Posted by regular guy

I'm not going to say the Clevite journal clearance white paper is the end-all or definitive source. But I will say the only engine on this list that violates that spec, and 80 years of engine design best practice is the S65. The S65 is 16% smaller than the minimum value recommended by that spec.

Understood.

One more question.

Devils advocate- Lets say BMW purposely violated the best practices. What would be the reason?

I have read that NASCAR engines are hand built to have tight clearances and run very thin oils. The advantage of the tight clearances is the amount of oil the engine has to push around and oil pressures required. As a result some power is "saved".

Is there any rule/rough estimate about how much power is gained from using tighter clearances and thinner oils?

Better question, if someone were to correct their S65 but not upgrade to a "stroker" would a thicker oil be required? Would their be a significant loss of power?

[regular guy]

Originally Posted by JEllis

Understood.

One more question.

Devils advocate- Lets say BMW purposely violated the best practices. What would be the reason?

According to the Clevite white paper, there are two reasons: 1) quieter engine operation, and 2) a little more horsepower. But also according to the Clevite white paper, they issue a very stern warning if you ever violate these specs, you MUST also mate the engine to a lighter weight oil (not 10W60).

I have read that NASCAR engines are hand built to have tight clearances and run very thin oils. The advantage of the tight clearances is the amount of oil the engine has to push around and oil pressures required. As a result some power is "saved".

I have good reason to think this is only a rumor. I have been in close contact with a NASCAR engine builder from one of the biggest NASCAR teams. He is one of the sources providing information for this thread. If this were the case, I'm sure he would have mentioned it to me.

Is there any rule/rough estimate about how much power is gained from using tighter clearances and thinner oils?

Better question, if someone were to correct their S65 but not upgrade to a "stroker" would a thicker oil be required? Would their be a significant loss of power?

For a "corrected" S65, whether stroker or not, I think the concensus is TWS 10W60 would be a great oil. We've talked about the power loss, and if I remember correctly, the estimate is 5hp or less difference. This was discussed publicly in one of the many threads. I'm just doing my best to remember it without looking it up. But I think it was estimated to be about 5hp difference, no more.

[JEllis]

Cool

NASCAR engine building I am sure is a fairly secretive process given they are all competing for tenths of a second.

I read it in the following article.

http://www.enginebuildermag.com/Arti...learances.aspx

Blurb from article:

"In a NASCAR engine, rules limit the minimum diameters of the rod and main journals on the crankshaft. The rods are 1.850˝ in diameter while the mains are 1.999˝. Most of these engines are running rod and main bearing clearances of .001˝ or less, and they are doing it with low viscosity racing oils such as 0W5, 0W30 and 0W50. These racing oils are as thin as water and are highly friction modified."

The following article appears to back up the first

http://www.precisionenginetech.com/t...g-tech-part-1/

Blurb from article

"According to MAHLE Clevite’s Bill McKnight, top NASCAR Cup teams are carefully selecting bearings and measuring each. They will typically order about 500 bearings and check each individual bearing shell for height (in terms of crush factor) and thickness, etc. They’ll carefully categorize each bearing as tight, loose or intermediate, which then allows them to pick and choose bearings depending on the specific engine application.

The trend among the Cup teams is to run tighter clearances, creating higher oil film pressure."

[Ronnydashore]

I tell you, some people make it seem like the bmw engineers are really dense and oblivious. I am quiet certain they had those measurements and ratios as well as knew the history of which oil the e46 used and the problems it had before/after the oil change. Again I think the 10w60 is not only because it runs at high temps but more importantly it very likely has other important reasons for its use aside from this focus on bearings.

An anonymous nascar engine builder takes way less credibility than the M division in my perspective

[pbonsalb]

I thought the E39 M5 and E46 M3 started with 5W30 and then once BMW did its deal with Castrol on the 10W60 development, BMW switched the required spec to 10W60. In other words, the change was due to BMW's deal with Castrol and the original engine designers actually specified a thinner oil. Any truth to this?

[catpat8000]

Originally Posted by pbonsalb

I thought the E39 M5 and E46 M3 started with 5W30 and then once BMW did its deal with Castrol on the 10W60 development, BMW switched the required spec to 10W60. In other words, the change was due to BMW's deal with Castrol and the original engine designers actually specified a thinner oil. Any truth to this?

Well I have no idea about any deals with Castrol but I bought a 2002 E46 M3 in late 2001, which would have been at the very start of the car's lifecycle and at that time 10W60 synthetic was required. So I don't think what you say could be true.

Pat

[Yellow Snow]

Originally Posted by catpat8000

Well I have no idea about any deals with Castrol but I bought a 2002 E46 M3 in late 2001, which would have been at the very start of the car's lifecycle and at that time 10W60 synthetic was required. So I don't think what you say could be true.

Pat

5w30 was definitely the first oil recommended for the E46 M3, then it changed to 10w60 when the bearing problems surfaced.

[CSBM5]

Originally Posted by pbonsalb

I thought the E39 M5 and E46 M3 started with 5W30 and then once BMW did its deal with Castrol on the 10W60 development, BMW switched the required spec to 10W60. In other words, the change was due to BMW's deal with Castrol and the original engine designers actually specified a thinner oil. Any truth to this?

No, for the E39 M5 it is exactly other way around. The 2000 models started with TWS and then effective 3/2000 production and later shifted to BMW Castol 5W30 synthetic. This coincided with a production change in the S62 engine using different piston rings. All E39 M5s from then on through the end of production specified BMW 5W30 synthetic oil as the spec oil. The owner's manuals in 2001 models were already printed apparently, so they pasted in a new page with the 5W30 oil spec. They also placed large stickers under the hood with the BMW 5W30 oil requirement starting with 2001 production.

Fast forward about 7 years to ~2008 timeframe and BMWNA switched their recommendation for the S62 back to TWS. No reason given. HUGE, and I mean HUGE threads exist on the M5board about this whole subject.

[speedaddictM3]

Originally Posted by Ronnydashore

An anonymous nascar engine builder takes way less credibility than the M division in my perspective

You mean the same M division that doesn't know how to make an engine that doesn't blow up?

[Dave07997S]

Originally Posted by pbonsalb

I thought the E39 M5 and E46 M3 started with 5W30 and then once BMW did its deal with Castrol on the 10W60 development, BMW switched the required spec to 10W60. In other words, the change was due to BMW's deal with Castrol and the original engine designers actually specified a thinner oil. Any truth to this?

You are correct about the E46 M cars starting out with 5W-30. My 2001 e46 M3 started with 5W30 then a few months of ownership I was told to bring the car to the dealer for a free oil change with the switch out to the 10W60 we now have today.

I think the E39 M5 already had this oil when the E46 M3 came out.

dave

[regular guy]

Originally Posted by Ronnydashore

I tell you, some people make it seem like the bmw engineers are really dense and oblivious. I am quiet certain they had those measurements and ratios as well as knew the history of which oil the e46 used and the problems it had before/after the oil change. Again I think the 10w60 is not only because it runs at high temps but more importantly it very likely has other important reasons for its use aside from this focus on bearings.

An anonymous nascar engine builder takes way less credibility than the M division in my perspective

Your anonymous sources from BMW M division are even less credible because you can't call upon them to chime in to this thread.

There are three things that you know for a fact:

1. There is a long standing clearance-to-journal ratio best practice rule that factory and racing engine builders alike have followed for 50+ years. This best practice clearance ratio is well documented in dozens of web sites, and recommended by Clevite, the maker of the S65 engine bearings. The S65 engine cuts that clearance ratio in half.
2. The bearing wear patterns we're seeing all match the Clevite online/interactive bearing failure diagnosis web site, example #12 "Oil Starvation / Marginal Oil Film Thickness." The main cause mentioned by Clevite for this type of failure is "too little bearing oil clearance."
3. There is also a long standing rod side clearance best practice rule that factory and racing engine builders alike have followed for quite some time. Best practice clearance ratio is well documented in dozens of web sites. The S65 engine cuts that clearance ratio by two orders of magnitude.

[regular guy]

Originally Posted by Yellow Snow

5w30 was definitely the first oil recommended for the E46 M3, then it changed to 10w60 when the bearing problems surfaced.

Originally Posted by CSBM5

No, for the E39 M5 it is exactly other way around. The 2000 models started with TWS and then effective 3/2000 production and later shifted to BMW Castol 5W30 synthetic.

Originally Posted by Dave07997S

You are correct about the E46 M cars starting out with 5W-30. My 2001 e46 M3 started with 5W30 then a few months of ownership I was told to bring the car to the dealer for a free oil change with the switch out to the 10W60 we now have today.

I think the E39 M5 already had this oil when the E46 M3 came out.

dave

Believe I have the answer to this at home. I believe I have an official BMW document that describes the S54 oil chronology. For S62 oil chronology, was already posted in #398 of this thread. For S62, I believe CSBM5 is correct. Last night when I input all the data, I thought I saw S54 matched the same thing. That's why I need to go back to the documents I have at home to confirm. BTW, look at footnote (3) for S85 engine if you want to know what break in oil BMW uses on S85/S65.

[Yellow Snow]

Originally Posted by regular guy

Your anonymous sources from BMW M division are even less credible because you can't call upon them to chime in to this thread.

There are three things that you know for a fact:

1. There is a long standing clearance-to-journal ratio best practice rule that factory and racing engine builders alike have followed for 50+ years. This best practice clearance ratio is well documented in dozens of web sites, and recommended by Clevite, the maker of the S65 engine bearings. The S65 engine cuts that clearance ratio in half.
2. The bearing wear patterns we're seeing all match the Clevite online/interactive bearing failure diagnosis web site, example #12 "Oil Starvation / Marginal Oil Film Thickness." The main cause mentioned by Clevite for this type of failure is "too little bearing oil clearance."
3. There is also a long standing rod side clearance best practice rule that factory and racing engine builders alike have followed for quite some time. Best practice clearance ratio is well documented in dozens of web sites. The S65 engine cuts that clearance ratio by two orders of magnitude.

Not so sure they can be considered facts yet.

I would imagine the M division consulted Clevite on best bearing practice for their application. They wouldn't just buy in bearings without both companies being in agreement on specs

[Billj747]

Originally Posted by regular guy

Your anonymous sources from BMW M division are even less credible because you can't call upon them to chime in to this thread.

There are three things that you know for a fact:

1. There is a long standing clearance-to-journal ratio best practice rule that factory and racing engine builders alike have followed for 50+ years. This best practice clearance ratio is well documented in dozens of web sites, and recommended by Clevite, the maker of the S65 engine bearings. The S65 engine cuts that clearance ratio in half.
2. The bearing wear patterns we're seeing all match the Clevite online/interactive bearing failure diagnosis web site, example #12 "Oil Starvation / Marginal Oil Film Thickness." The main cause mentioned by Clevite for this type of failure is "too little bearing oil clearance."
3. There is also a long standing rod side clearance best practice rule that factory and racing engine builders alike have followed for quite some time. Best practice clearance ratio is well documented in dozens of web sites. The S65 engine cuts that clearance ratio by two orders of magnitude.

What is Clevite's take on the tight tolerances specified in the S65? Do they still recommend that tolerance or their 'industry standard' tolerances for replacement bearings?