Bearing Banter

[REDBULL]

You can upgrade rod bearings, increase your oil interval frequency (5000-7500miles), ensure proper warm up and keep RPMs below 3k until then. do oil analysis and monitor bearing wear with every oil change

[swamp2]

Originally Posted by REDBULL

You can upgrade rod bearings...

Except that there is really no "upgrade". Sure some folks are tinkering and making some claims and gaining perhaps 1/10th of a thousandths in clearance...

[BMRLVR]

If the engine is being rebuilt, ensure that the rod and main bearing clearances are properly set ...... That is the main thing that can be done to increase longevity.

The vast majority of failures are related to the rotating assembly e.g. Main and rod bearing failures.

[swamp2]

Originally Posted by BMRLVR

If the engine is being rebuilt, ensure that the rod and main bearing clearances are properly set ...... That is the main thing that can be done to increase longevity.

The vast majority of failures are related to the rotating assembly e.g. Main and rod bearing failures.

Has there ever been a single case of main bearing failure? Not that I have seen.

What is "properly set", factory values?

There is no "solution" less custom crank undersizing AFAIK. It's also still debatable if BMW bearing clearances have caused any lack of reliability so hence I refer to this a a "solution".

[regular guy]

Originally Posted by swamp2

Has there ever been a single case of main bearing failure? Not that I have seen.

Yes, there have been a few cases of main bearing failure. I posted pictures of an engine with damaged main bearings and damaged crankshaft; but that engine didn't actually fail (yet). Here's the first one that I know of (main bearing failure):
http://www.m3post.com/forums/showthread.php?t=379712

[BMRLVR]

Originally Posted by swamp2

Has there ever been a single case of main bearing failure? Not that I have seen.

What is "properly set", factory values?

There is no "solution" less custom crank undersizing AFAIK. It's also still debatable if BMW bearing clearances have caused any lack of reliability so hence I refer to this a a "solution".

Yes there has been a few cases of main bearing failures, one of these failures that I am aware of actually damaged a main journal beyond repair.

The factory has no published values so you know I am not referring to that. How do you still hang on to the fact that there is no problem when random people are still losing engines. What do you think caused this guy's hole in the block if it wasn't a thrown rod?

I gave the OP my opinion, based on my background I think my opinion is worth something. Go grab a textbook and read some more about engine failures while I actually work on and repair real life engines with my own hands.

[swamp2]

Originally Posted by BMRLVR

Yes there has been a few cases of main bearing failures, one of these failures that I am aware of actually damaged a main journal beyond repair.

The factory has no published values so you know I am not referring to that. How do you still hang on to the fact that there is no problem when random people are still losing engines. What do you think caused this guy's hole in the block if it wasn't a thrown rod?

I gave the OP my opinion, based on my background I think my opinion is worth something. Go grab a textbook and read some more about engine failures while I actually work on and repair real life engines with my own hands.

All engines exhibit failures, it is a question of frequency, period. You may think the S65 failure rate is outrageously high, but all data shows it to be quite low and very suspiciously concentrated in the US.

However, as to your second point, nominal factory values are established and they are, for the new bearings (702/703), basically inside the narrowest "rule of thumb" range, whereas the older ones (088/089) are just outside of this "rule". If you are going to give the guy advise, you should probably say a lot more than have clearances "properly set". If you think all rebuilds should have custom ground rod journals, say that.

I think your opinion is certainly worth something, but so is mine. We've debated this academics/textbook vs. hands-on thing before and I don't think you really want to go down that path again do you?

[swamp2]

Originally Posted by regular guy

Here's the first one that I know of (main bearing failure):
http://www.m3post.com/forums/showthread.php?t=379712

That's clearly not a failure, wear yes, unacceptable wear maybe, failure no. The engine was running.

[s85e90]

Originally Posted by BMRLVR

Yes there has been a few cases of main bearing failures, one of these failures that I am aware of actually damaged a main journal beyond repair.

The factory has no published values so you know I am not referring to that. How do you still hang on to the fact that there is no problem when random people are still losing engines. What do you think caused this guy's hole in the block if it wasn't a thrown rod?

I gave the OP my opinion, based on my background I think my opinion is worth something. Go grab a textbook and read some more about engine failures while I actually work on and repair real life engines with my own hands.

cause you said it yourself. This is still a random issue with much more cars driving on the road than blowing up. I know a little bit about cars and have built many myself, and I will still stand to say this is magnified due to the forums presenting those only w/ problems.

[BMRLVR]

Originally Posted by s85e90

cause you said it yourself. This is still a random issue with much more cars driving on the road than blowing up. I know a little bit about cars and have built many myself, and I will still stand to say this is magnified due to the forums presenting those only w/ problems.

Not saying that the issue is huge, but it is definitely present and there are many cases of premature bearing wear documented on here. The cases on here are also not showing the possible engine issues from owners not on the forums.

Anyhow, the OP asked for a way to increase reliability and since his engine has failed and he needs to source a replacement, it would be smart to add some clearance since he has the opportunity to do so!

[BMRLVR]

Originally Posted by swamp2

That's clearly not a failure, wear yes, unacceptable wear maybe, failure no. The engine was running.

It would have failed if it had been ran longer....... The engine had ~ 12,000 miles on it.

[regular guy]

Originally Posted by swamp2

All engines exhibit failures, it is a question of frequency, period. You may think the S65 failure rate is outrageously high, but all data shows it to be quite low and very suspiciously concentrated in the US.

I don't think it's so suspicious when you're reading an English speaking web site and the USA language is English. What else did you expect to find here...failures in Denmark, Japan, Russia?

Originally Posted by swamp2

That's clearly not a failure, wear yes, unacceptable wear maybe, failure no. The engine was running.

There was main bearing failure. It's a documented case. Maybe the pictures didn't match because I didn't look hard enough. But elmariachi did chime in to a thread recently and confirmed he suffered from main bearing failure.

[swamp2]

Originally Posted by BMRLVR

It would have failed if it had been ran longer....... The engine had ~ 12,000 miles on it.

Not trying to "push you buttons" but you can say the above about ANY engine... The question is how much longer might it have ran and neither of us can answer that with any accuracy at all...

[swamp2]

Originally Posted by regular guy

I don't think it's so suspicious when you're reading an English speaking web site and the USA language is English. What else did you expect to find here...failures in Denmark, Japan, Russia?

This is clearly the most popular and well trafficked BMW forum. We have members from all over the world on many continents, including regular posters from EU (Germany, UK and France), Asia and Australia. Despite that the failures are pretty well exclusively in the US. To most of us this is a well discussed and unsolved dilemma.

Originally Posted by regular guy

There was main bearing failure. It's a documented case. Maybe the pictures didn't match because I didn't look hard enough. But elmariachi did chime in to a thread recently and confirmed he suffered from main bearing failure.

I can only go by what you posted...

[regular guy]

Originally Posted by swamp2

I can only go by what you posted...

Then go by this:

http://www.m3post.com/forums/showpos...&postcount=169

[swamp2]

Originally Posted by regular guy

Then go by this:

http://www.m3post.com/forums/showpos...&postcount=169

I don't see anything there other than him verifying your prompt that "the mains failed?". It seems clear (and the dates are consistent) his is referring back to the entire thread/story about his case in the prior link you provided. And again that was not main bearing failure...

[regular guy]

Originally Posted by swamp2

I don't see anything there other than him verifying your prompt that "the mains failed?". It seems clear (and the dates are consistent) his is referring back to the entire thread/story about his case in the prior link you provided. And again that was not main bearing failure...

There is ample discussion in his thread about main bearing failure. Whether it was cause or effect is a semantics question that I don't care about.

[coloradoe92m3]

If this was really an issue with the specs being too tight, wouldn't a lot more fail? Seems more consistent with the occasional failure to perhaps be out of spec and failing, otherwise how would vast majority be totally fine?

[regular guy]

Originally Posted by coloradoe92m3

If this was really an issue with the specs being too tight, wouldn't a lot more fail? Seems more consistent with the occasional failure to perhaps be out of spec and failing, otherwise how would vast majority be totally fine?

This is all discussed in the bearing wiki thread. For the most part, this is the same things I have said all along. The specs are tight, and when you add tolerance stack up (the occasional two parts being out of spec but mated together), then things go boom. But saying the vast majority are totally fine is probably incorrect. So far, all but one set of bearings ever taken out, photographed, and displayed on the forums didn't look totally fine. And that one set of bearings that did look pretty decent only had 16k miles on them.

[swamp2]

Originally Posted by regular guy

This is all discussed in the bearing wiki thread. For the most part, this is the same things I have said all along. The specs are tight, and when you add tolerance stack up (the occasional two parts being out of spec but mated together), then things go boom. But saying the vast majority are totally fine is probably incorrect. So far, all but one set of bearings ever taken out, photographed, and displayed on the forums didn't look totally fine. And that one set of bearings that did look pretty decent only had 16k miles on them.

And the actual measured tolerances for both the journals and bearings all show incredibly tight tolerances. Thus there is no observational evidence whatsoever supporting this speculation as the true cause. Yes, again, beating the dead horse... The hypothesis seems reasonable on the surface and I agree it is probably the best hypothesis we have yet, but it is a very long way from being able to be elevated to an actual theory...

[regular guy]

Originally Posted by swamp2

And the actual measured tolerances for both the journals and bearings all show incredibly tight tolerances. Thus there is no observational evidence whatsoever supporting this speculation as the true cause. Yes, again, beating the dead horse... The hypothesis seems reasonable on the surface and I agree it is probably the best hypothesis we have yet, but it is a very long way from being able to be elevated to an actual theory...

Well then thank goodness I didn't use the word "theory" anywhere in my post. I can only imagine how long the tongue lashing (aka chest beating) would be if I had.

[swamp2]

Originally Posted by regular guy

Well then thank goodness I didn't use the word "theory" anywhere in my post. I can only imagine how long the tongue lashing (aka chest beating) would be if I had.

Wow, what a utterly weak point...

You don't need to use the word theory, your matter of fact style when presenting this speculation provides the implication for you. Reread your own post I replied to! Please tell me that it does not sound like it is a foregone and certain conclusion as to what the exact cause of all of the bearing related failures is. Once you disagree with this observation you can get back to accusing me a chest beating.