Official S65 Rod Bearing Condition Example Thread

Assimilator1 wrote

One small correction , ACL's H STD has slightly bigger clearances (measured & specs) than the both OEM bearings according to the bearing wiki.

Yes, but not really a correction just more semantics in nomenclature, and another reason to look at numbers over names. ACL and others identify their bearings by STD or not STD. The bearing was designed for a STD journal.

Strictly speaking, pretty much every aftermarket bearing for the S65 "STD" journal yields greater than OEM clearances (yet are not always marketed as "extra clearance"). I've never seen any bearings measure tighter than OEM shells.

Fair enough

Btw, re an earlier question I posted, I found from ACLs pdf that their babbitt layer (overlay) is 0.013mm thick.
Any idea what BE's is?

Assimilator1 wrote

Fair enough

Btw, re an earlier question I posted, I found from ACLs pdf that their babbitt layer (overlay) is 0.013mm.
Any idea what BE's is?

No, it would be a question for BE to decide whether or not to publish that info.

deansbimmer wrote

Yes, but not really a correction just more semantics in nomenclature, and another reason to look at numbers over names. ACL and others identify their bearings by STD or not STD. The bearing was designed for a STD journal.

Strictly speaking, pretty much every aftermarket bearing for the S65 "STD" journal yields greater than OEM clearances (yet are not always marketed as "extra clearance"). I've never seen any bearings measure tighter than OEM shells.

Can you measure a negative clearance?

Assimilator1 wrote

I asked him the exact same question above & he answered me .


You're not giving us anywhere near enough info, did a bolt let go? Or did the bearing seize causing the failure? Got any pics?

Sorry to hear about your blown engine btw

Well, I had my 2011 E92 S65 Rod bearings changed, when it was operating fine, the car had been to the track by previous owner, and I drove it down from Chicago to FL before the Rod Brg change. I had the shop install ACL bearings and Carrillo Rod bolts. The engine blew the next day at the track, the first session after warm up. The ACL bearings are supposed to be undersize ~0.025" (or more oil clearance). I have not taken the engine out yet to determine root cause.

Shit! Sorry to hear that man
Let us know what the outcome is.

Re your ACL bearings, do you mean ACL std HX? (+0.0025mm, 0.001" clearance).

Just realised you posted on the previous page.
Only failures I've heard of after big end bearing replacement have been a few engines main bearings failure. So not the big ends themselves.
You mentioned the bearing cap hitting the block, off hand I can only think of 2 likely ways this can happen.
Oil starvation>bearing seizing>rod/cap breaking, or rod bolts not being tightened properly, coming loose then rod cap breaking.
I suppose it is possible a badly made rod bolt could break, but I would think that is exceedingly unlikely!

kiquos wrote

I had the shop install ACL bearings and Carrillo Rod bolts. The engine blew the next day at the track, the first session after warm up. The ACL bearings are supposed to be undersize ~0.025" (or more oil clearance). I have not taken the engine out yet to determine root cause.

Yikes please create a thread when you do an engine tear down. There have been a few cases of install error when doing rod bearings. There have also been atleast 1 case, maybe more, of main bearings going after a rb change (properly done).

Eitherway, hope you get it sorted.

Do you recall what those install errors were?

Assimilator1 wrote

Shit! Sorry to hear that man
Let us know what the outcome is.

Re your ACL bearings, do you mean ACL std HX? (+0.0025mm, 0.001" clearance).

Btw ACL std HX are the extended ones targeting 0.0025" clearance (0.063mm), e.g. ind standard 0.001"/inch crank + another 0.0005".

Interesting, where did you get the 0.063mm total (nominal?) clearance from?
The bearing wiki states 0.0737mm nominal clearance for ACL's HX shells.

I'm still trying to decipher this correspondence from ACL.....

Assimilator1 wrote

Interesting, where did you get the 0.063mm total (nominal?) clearance from?
The bearing wiki states 0.0737mm nominal clearance for ACL's HX shells.

I'm still trying to decipher this correspondence from ACL.....

Yep I'm aware of BE's measurements which obviously is true for that specific hardware. However the way they present it suggesting its a spec valid for all engines I never quite understood.

ACL own specs in mm
Shaft 51.975 - 51.991. Housing 56.000 - 56.013. HX Shell variance 1.977 - 1.985
Min clearance: 56.000 – 51.991 – 2x1.985 = 0.039mm (0.00153"
Max clearance: 56.013 – 51.975 – 2x1.977 = 0.084mm (0.00331")

Hence FWIW ACL Nominal clearance would end up on (0.084+0.039)/2 = 0.0615mm (0.00242") i.e. fairly close to Clevite's rule of thumb, 0.0025 inch for our 2 inch crank diameter.
BE are using their own tighter shaft spec based on measured cranks (while housing spec is BMW official). Using this ACL HX would tighten up to 0.0413 – 0.0805mm, with Nominal 0.06085mm (0.0024").

Thanks for deciphering those numbers , where did you get the shell variance numbers from though? (back worked it?).

So if I've got it right, for the H shells (I'm lacking the min variance figures).
Min clearance: 56.000 – 51.991 – 2x1.998 = 0.013 mm (0.00051")
Max clearance: 56.013 – 51.975 – 2x1.9?? = 0.058*mm (0.00228")
Nominal clearance = 0.0355mm (0.0014")

*figure from my earlier link.

Woah! At the min end that's far too tight clearance, & even worse than BMWs original shells!
How come the wiki bearings H measurements were so much better? Were those based on the particular shells they got? In which case, presumably they got a good middling to upper end set? (clearance wise).

So that rules out the H shells for me then, sounds like a mix of the ACL H & HXs would be better, just trying to think what the clearance range would be for that.....
Min/max = 0.025mm to 0.07mm? (0.00098" to 0.00275") (not including shell variance though). Have I got the maths right??
If so, then even that lower end is still too low really, guess it would have to be the HXs then if I went the ACL route.

Assimilator1 wrote

Thanks for deciphering those numbers , where did you get the shell variance numbers from though? (back worked it?).

So if I've got it right, for the H shells (I'm lacking the min variance figures).
Min clearance: 56.000 – 51.991 – 2x1.998 = 0.013 mm (0.00051")
Max clearance: 56.013 – 51.975 – 2x1.9?? = 0.058*mm (0.00228")
Nominal clearance = 0.0355mm (0.0014")

*figure from my earlier link.

Woah! At the min end that's far too tight clearance, & even worse than BMWs original shells!
How come the wiki bearings H measurements were so much better? Were those based on the particular shells they got? In which case, presumably they got a good middling to upper end set? (clearance wise).

So that rules out the H shells for me then, sounds like a mix of the ACL H & HXs would be better, just trying to think what the clearance range would be for that.....
Min/max = 0.025mm to 0.07mm? (0.00098" to 0.00275") (not including shell variance though). Have I got the maths right??
If so, then even that lower end is still too low really, guess it would have to be the HXs then if I went the ACL route.

Or get some BE shells...

Yea, that's what I 1st looked at (& would prefer), but they're really expensive! 3x more than the ACLs! .

Interestingly, a garage (Redish Motorsport) over here which has done a good number of big end bearing changes on S65s, uses the ACL std H bearings & they find the clearances to be(using plastigauges).

Assimilator1 wrote

Yea, that's what I 1st looked at (& would prefer), but they're really expensive! 3x more than the ACLs! .

Interestingly, a garage (Redish Motorsport) over here which has done a good number of big end bearing changes on S65s, uses the ACL std H bearings & they find the clearances to be about 0.05mm (using plastigauges).

Plastigauge is meaningless. Plain and simple.

Any shop that quotes clearance using that is not a great shop.

And on cost: your S65 is a very expensive engine. I cannot fathom why saving a few hundred dollars is something to worry about for a job like this.

Do it once. Do it right.

Cheers,

Assimilator1 wrote

Thanks for deciphering those numbers , where did you get the shell variance numbers from though? (back worked it?).

So if I've got it right, for the H shells (I'm lacking the min variance figures).
Min clearance: 56.000 – 51.991 – 2x1.998 = 0.013 mm (0.00051")
Max clearance: 56.013 – 51.975 – 2x1.990 = 0.058*mm (0.00228")
Nominal clearance = 0.0355mm (0.0014")

*figure from my earlier link.

Woah! At the min end that's far too tight clearance, & even worse than BMWs original shells!
How come the wiki bearings H measurements were so much better? Were those based on the particular shells they got? In which case, presumably they got a good middling to upper end set? (clearance wise).

So that rules out the H shells for me then, sounds like a mix of the ACL H & HXs would be better, just trying to think what the clearance range would be for that.....
Min/max = 0.025mm to 0.07mm? (0.00098" to 0.00275") (not including shell variance though). Have I got the maths right??
If so, then even that lower end is still too low really, guess it would have to be the HXs then if I went the ACL route.

As mentioned the clearance numbers are from ACL's spec, where they quote Max/Min clearance (based on above shaft/housing specs) and a bearing thickness (Max wall at crown). Their bearings keep a max 0.008mm variance so there you have your 0.058 max on the Standard shell. Again, this is where BE shine with a zero variance on the total shell thickness due to matching the pair.

Keep in mind minimum and maximum clearance is absolutely worse case with all three components involved, which might been the case in the after all relatively few cases of engine blown up (+possible lack of maintenance and abuse).
Ps. Assuming a normal production distribution ("bell curve"), which I obviously have no insight into.

My thoughts on mixing shells is blunt and may offend some, but it's honest. It's a great practice. But(!) if you have to post or inquire on how to do it, how to measure it, seek a second opinion, or for any reason are not certain about any aspect of how to perform it- you should buy BE bearings and know it has been done right.

ACL bearings are excellent! Mixed sets are great when done correctly.

deansbimmer wrote

My thoughts on mixing shells is blunt and may offend some, but it's honest. It's a great practice. But(!) if you have to post or inquire on how to do it, how to measure it, seek a second opinion, or for any reason are not certain about any aspect of how to perform it- you should buy BE bearings and know it has been done right.

ACL bearings are excellent! Mixed sets are great when done correctly.

Lang racing also sell measured beating sets by ACL. So another good choice.

Lang also sells ACL mixed sets.

Shout out to SSR Performance for my bearings. Very happy with their service. Car feels great everything is smooth and as you can see I've had some wear. It's noted the car is a 2011 but it was a typo my car is a 2008. Miles are correct 55,942. I would change my oil every 4500-5000 miles, never been tracked but lots of mountain abuse lol. It definitely is a piece of mind!

E92Gok wrote

Shout out to SSR Performance for my bearings. Very happy with their service. Car feels great everything is smooth and as you can see I've had some wear. It's noted the car is a 2011 but it was a typo my car is a 2008. Miles are correct 55,942. I would change my oil every 4500-5000 miles, never been tracked but lots of mountain abuse lol. It definitely is a piece of mind!

What bearings did you go with?

NQRDDS wrote

E92Gok wrote

Shout out to SSR Performance for my bearings. Very happy with their service. Car feels great everything is smooth and as you can see I've had some wear. It's noted the car is a 2011 but it was a typo my car is a 2008. Miles are correct 55,942. I would change my oil every 4500-5000 miles, never been tracked but lots of mountain abuse lol. It definitely is a piece of mind!

What bearings did you go with?

I went with BE bearings