Connecting Rod Bolts

[BMWahba]

Just buy them. In Europe are availables.

Do you have a part number for the older M11 bolts? Are these the same as the S50 euro bolts?

[Slideways]

I need to find out what bolts my 12/15/2002 build car has. The TSB states that cars built after 12/13/2002 are using updated M10 bolts....so being 3 days away from that cutoff I wonder if I had a 3 day older engine or something and have M11 bolts, lol. FCP says cars after 2/2003 have M10's. Weird.

You should get the OE M10s to have on hand before you start the job. Original engine in a 11/02 came with the M10s.

As for the ARP, Lang tested both the ARP M11s and ARP M10s and from memory, they stated that the M11s had the correct clamping force and the M10s did not when using the ARP torque specs. It would be great if Lang could verify this again as the thread was lost with the old forum.

[tnord]

Here's what I found from Lang's page regarding old/new OE, and ARP bolts. This discussion is of particular interest to me as Chicane will be doing mine at the end of the month, and has suggested ARP. I believe I have a 9/02 build.

S54 engines manufactured prior to 2003 come with larger rod bolt that are not supposed to be replaced according to BMW TIS. The later engines use a rod bolt that is smaller (torx head) and is one time use. On the early engines we prefer to use ARP fasteners because we don’t know the condition of the stock rod bolt. On the newer 2003+ engines we have found that the stock bolt is completely reliable and a bit cheaper than the ARP bolts so we will typically use those unless the customer requests ARP bolts. In our bench testing we found that the ARP bolt in the 2003 and newer engine needs to be stretched beyond the ARP specification to achieve the same bore shape as the stock BMW bolt.

A benefit of the ARP bolt design is that it allows us to use the rod stretch gauge to preload the fasteners. Because the rod bolt is arguably the most critical bolt in the engine, we like being able to use the most accurate method we can for tightening it. By using rod bolt stretch we have found that depending on conditions the torque can vary as much as 10ft lbs from fastener to fastener to achieve the same stretch. Using ARP hardware take slightly more time using the stretch method but we believe the peace of mind and longevity is worth it on the earlier engines. Another benefit of the ARP bolts is that they can be reused in the future instead of replacing them in the future. This is particularly useful on a track or race car that will be serviced frequently.

[BMWahba]

You should get the OE M10s to have on hand before you start the job. Original engine in a 11/02 came with the M10s.

As for the ARP, Lang tested both the ARP M11s and ARP M10s and from memory, they stated that the M11s had the correct clamping force and the M10s did not when using the ARP torque specs. It would be great if Lang could verify this again as the thread was lost with the old forum.

That's good to know. Fingers crossed I do have the M10s.

Here's what I found from Lang's page regarding old/new OE, and ARP bolts. This discussion is of particular interest to me as Chicane will be doing mine at the end of the month, and has suggested ARP. I believe I have a 9/02 build.

S54 engines manufactured prior to 2003 come with larger rod bolt that are not supposed to be replaced according to BMW TIS. The later engines use a rod bolt that is smaller (torx head) and is one time use. On the early engines we prefer to use ARP fasteners because we don’t know the condition of the stock rod bolt. On the newer 2003+ engines we have found that the stock bolt is completely reliable and a bit cheaper than the ARP bolts so we will typically use those unless the customer requests ARP bolts. In our bench testing we found that the ARP bolt in the 2003 and newer engine needs to be stretched beyond the ARP specification to achieve the same bore shape as the stock BMW bolt.

A benefit of the ARP bolt design is that it allows us to use the rod stretch gauge to preload the fasteners. Because the rod bolt is arguably the most critical bolt in the engine, we like being able to use the most accurate method we can for tightening it. By using rod bolt stretch we have found that depending on conditions the torque can vary as much as 10ft lbs from fastener to fastener to achieve the same stretch. Using ARP hardware take slightly more time using the stretch method but we believe the peace of mind and longevity is worth it on the earlier engines. Another benefit of the ARP bolts is that they can be reused in the future instead of replacing them in the future. This is particularly useful on a track or race car that will be serviced frequently.

I am kind of hoping I do have the M10's to eliminate this worry lol and just go OEM. Sounds like if you've got M11's you should probably go ARP, as I expected due to the fact that you can't buy replacement OEM M11's afaik...unless the Euro S50 bolts are the same.

[Tbonem3]

Same boat, 02/02 so M10, but the recall was done at like 16k, so already reused once. I think/hope I can reuse them again.

[BMWahba]

Same boat, 02/02 so M10, but the recall was done at like 16k, so already reused once. I think/hope I can reuse them again.

You mean M11

[Tbonem3]

You mean M11

Ya

[BMWahba]

Ya

Re-using them twice seems like something I would prefer not to do... we will find out once I crack it open. I think based on all this info in this thread, if you've got older M11, maybe just run the ARPs.

[Tbonem3]

I can't believe BMW gave us this info, but didn't say how many reuses.

[BMWahba]

I can't believe BMW gave us this info, but didn't say how many reuses.

Lol classic. They never thought of it as a wear-item I would presume....only as a one-time fix with their "updated" shells. For those of us who subscribe to the ideology of changing them out after 60-80k....figure it out I guess? lol

[Tbonem3]

I was reading on cutters that you should keep the M11s, as each is matched to its rod/cap.

[heinzboehmer]

I think/hope I can reuse them again.

Re-using them twice seems like something I would prefer not to do... we will find out once I crack it open. I think based on all this info in this thread, if you've got older M11, maybe just run the ARPs.

I know a single point of data doesn't make something true, but my engine has 11.5k mi on its third set of bearings with the original M11 bolts and everything has been fine.. BMW replaced the originals under the recall at 35k mi and I replaced them again at 113.5k mi. Bolts were reused twice. Engine is now at 125k mi.
I think the M11 bolts must not be torqued to yield. I doubt BMW spent all that money replacing the bearings on early cars to avoid engine failure but decided to reuse a cheap critical fastner and risk having those engines fail anyway. So if they're not torque to yield, those bolts can technically be reused forever, as long as they're torqued properly every time.

Considering the second set of bearings on my engine came out after 78.5k mi with virtually no wear, I think it's safe to assume that proper torquing procedures were followed on my car. But yeah no way to verify that a 200lb gorilla didn't over torque and stretch the bolts on other cars.

I wish BMW sold the M11 bolts so that there was no need to guess about the condition of the ones on the engine. If you don't trust the old bolts, then ARP with a stretch guage are probably your best bet.

[Tbonem3]

That's all I needed! Thanks. I want to DIY and cheaply, so reusing and the simpler torquing procedure is key!

[BMWahba]

I know a single point of data doesn't make something true, but my engine has 11.5k mi on its third set of bearings with the original M11 bolts and everything has been fine.. BMW replaced the originals under the recall at 35k mi and I replaced them again at 113.5k mi. Bolts were reused twice. Engine is now at 125k mi.
I think the M11 bolts must not be torqued to yield. I doubt BMW spent all that money replacing the bearings on early cars to avoid engine failure but decided to reuse a cheap critical fastner and risk having those engines fail anyway. So if they're not torque to yield, those bolts can technically be reused forever, as long as they're torqued properly every time.

Considering the second set of bearings on my engine came out after 78.5k mi with virtually no wear, I think it's safe to assume that proper torquing procedures were followed on my car. But yeah no way to verify that a 200lb gorilla didn't over torque and stretch the bolts on other cars.

I wish BMW sold the M11 bolts so that there was no need to guess about the condition of the ones on the engine. If you don't trust the old bolts, then ARP with a stretch guage are probably your best bet.

Great info and data point, thank you sir.

[ZiMMie]

Technically we should able to use the bolts(early build cars) as much as we want as long as they are torque to specification every single time.

when i did my rebuilt i went with ARP since i got a good deal. If were to do it again, ill stay with the OE bolts.