Rod bearing options.

[MotorSportThree]

Finally going to tackle the last of the big three. I’m sure this has been discussed plenty of times, but which rod bearings are recommended. Was thinking of going with ACL bearings. Is there really a wrong option?

thanks in advance

pic of my car just cause.

[Sprp85]

From what I've gathered while planning for the job recently;

• Stick with the original clearance spec bearings - WPC treated OE/OE/BE/ACL didn't seem to matter much.
• Stick with OE rod bolts

[cobra]

I just went OE. It lasted 100k miles. Should last another 100k.

[Obioban]

OE for me, with OE bolts to match.

[Cubieman]

Too bad ARP bolts are not generally accepted, at least around here, I have done a few S85 rod bearing jobs and just simply having to torque one time is pretty nice.

With the factory bolts does one leave the adjoining rod bolt basically just loose while completing all 3 torque sequences on other bolt or do you snug it down a bit?

Also with the 105° angle I imagine running into things with the tool, I am thinking of a 3/8" Techangle for this job, they are somewhat compact.

[DoubleSidedTape]

You do the torque procedure for both bolts on each rod, so the 5nm on each bolt, 30nm on each bolt, etc.

[George Hill]

Finally going to tackle the last of the big three. I’m sure this has been discussed plenty of times, but which rod bearings are recommended. Was thinking of going with ACL bearings. Is there really a wrong option?

thanks in advance

I only use OE and only replace the bolts if the repair procedure calls for it and when I do its with OE.

[Cubieman]

You do the torque procedure for both bolts on each rod, so the 5nm on each bolt, 30nm on each bolt, etc.

Yea, I get that all bolts are torqued, just wondering if hand tight was cool on one rod bolt while you did the opposite bolt on the same rod.

[George Hill]

Too bad ARP bolts are not generally accepted, at least around here, I have done a few S85 rod bearing jobs and just simply having to torque one time is pretty nice.

With the factory bolts does one leave the adjoining rod bolt basically just loose while completing all 3 torque sequences on other bolt or do you snug it down a bit?

Also with the 105° angle I imagine running into things with the tool, I am thinking of a 3/8" Techangle for this job, they are somewhat compact.

A different bolt design will provide a slightly different clamping force than OE. Check out the S65 bearing wiki and Robert posts how generic S65/S85 ARP rod bolts distort the connecting rod big end: http://wiki.rcollins.org/core/index....5_Rod_Bearings

While that is directly in reference to S65/S85 we can still apply the same theory here. FWIW I only use the BE spec ARP bolts on S65/85 engines.

Lastly, a 3/8" tech angle will be getting close to maxing out on the 105* stroke. I should buy a 1/2" one of these days, but I do the 5 & 30nm with my 3/8" and then I use a 1/2" ratchet on a mechanical dial for the 105*. The increased leverage is so worth the extra effort in setup. *BTW I've done a hundred or more engines this way.

[George Hill]

Yea, I get that all bolts are torqued, just wondering if hand tight was cool on one rod bolt while you did the opposite bolt on the same rod.

bolt 1 to 5nm, bolt 2 to 5nm,
bolt 1 to 30nm, bolt 2 to 30nm
bolt 1 to 105*, bolt 2 to 105*

[Cubieman]

Got it, DoubleSidedTape was telling me the same thing as well, I just read it wrong.

[Lee_Enfield]

I went with BE. Mind you only have a few thousand km and don't really track.

I did have a few questions and BE replied very quickly so at least the customer service is good.

[tlow98]

A different bolt design will provide a slightly different clamping force than OE. Check out the S65 bearing wiki and Robert posts how generic S65/S85 ARP rod bolts distort the connecting rod big end: http://wiki.rcollins.org/core/index....5_Rod_Bearings

While that is directly in reference to S65/S85 we can still apply the same theory here. FWIW I only use the BE spec ARP bolts on S65/85 engines.

Lastly, a 3/8" tech angle will be getting close to maxing out on the 105* stroke. I should buy a 1/2" one of these days, but I do the 5 & 30nm with my 3/8" and then I use a 1/2" ratchet on a mechanical dial for the 105*. The increased leverage is so worth the extra effort in setup. *BTW I've done a hundred or more engines this way.

In the case where you cannot verify which rod bolt has come out of which hole… would you use still use OE bolts?

Referring to the early M11 rod bolts. The later ones are on time use.

Im in a situation where the OE rod bolts were mixed up and they have been torqued 3-4x each. Was thinking the ARP bolts might actually make sense.

[George Hill]

In the case where you cannot verify which rod bolt has come out of which hole… would you use still use OE bolts?

Referring to the early M11 rod bolts. The later ones are on time use.

I asked a BMW engineer about this years ago when I rebuild my first S54 (Z3M Roadster) and the machine shop didn't label which bolt came out of which side of the rod. I was told it didn't matter and they only stated that to reduce the chance of techs making some random mistake. YMMV, that engine is still going, but I do try my best to not mix them up just incase.

If the rods are out of the block then I would measure the bores with everything torqued and make a decision at that time.

[bigjae46]

S54s are getting more expensive. At least with OEM you get a known quantity and possibly a warranty (2yr/unlimited miles of genuine BMW parts). Although with the warranty...you'll be in for a fight to get BMW to warranty an engine for a bad rod bearing or bolt.

I'm sure ACL is fine but how much are you really saving?

BE bearings worked with some guy and did extensive testing on the S65 which is very similar to the S85. I'd argue the rod bearings are more of an issue on the E9X M3 platform and for a different reason. I'm not sure if BE or the engineer dude went to the same length in testing the S54.