Rod Bearings and Bolts

[Shonky]

I had my bearings done yesterday by a guy who is one of the absolute guru's of BMW where I live and he said the same thing. Re-using the M11's is totally ok and preferable to ARP's.

That was never really under debate. BMW themselves say you can reuse the M11 bolts in the early engines. In fact they even say they shouldn't be replaced at all.

[0-60motorsports]

I had my bearings done yesterday by a guy who is one of the absolute guru's of BMW where I live and he said the same thing. Re-using the M11's is totally ok and preferable to ARP's.

M11, 100% agreed.

[headlock]

I was of the same opinion up until very recently. I had my motor rebuilt by a race engine builder who has put together countless S54's for road and race applications since they were new, and is well regarded as the best in NZ. He was very confident the bolts could be reused and that it was even preferable to the ARP bolts as they oval the rod bore and start to create tolerance issues (unless the rod is completely removed from the motor so the bore can be mic'd and the bearing can be sized correctly for the perfect roundness etc etc which in this case is unlikely). As to how many times they can be reused, it's anybody's guess.

I had my bearings done yesterday by a guy who is one of the absolute guru's of BMW where I live and he said the same thing. Re-using the M11's is totally ok and preferable to ARP's.

[0-60motorsports]

https://www.amazon.com/dp/B079G56GR4

Thanks!

[Thoglan]

I've said it for ages. There is no reason to 'run in' big end bearings. Someone on here even emailed one of the bearing manufacturers asking about run in and they said no run in is required and is their recommendation. Can't remember who it was though.

[Tbonem3]

No, you're right. The break in for bottom end makes no sense other than just "playing it safe."

[tnord]

I outsourced this job as a preventative measure to Chicane (PerkM3's shop for those that remember), and they put in WPC coated bearings and ARP hardware. Soliciting thoughts and supporting documentation regarding a "break in period."

I don't think there really needs to be one, as I think of break in related to new rings and cylinder honing. But maybe I'm missing something.

[lmattiso]

Yeah, I have no idea what bolts to order when I do mine. Mine is an 03, pre-LCI, but had the RB recall done in 05.

Run your VIN on a VIN decoder to get the actual production date. Mine is an early 2003 also and the production date is 12/10/2002 so in theory, I should have the M11's installed but will be curious to see once I open it up. I used this site to get my date: http://bimmer.work/ but there's a bunch out there.

[Slideways]

Yeah, I have no idea what bolts to order when I do mine. Mine is an 03, pre-LCI, but had the RB recall done in 05.

What is the build date? The full service records on the dealership's computers could tell which recall kit they ordered, whether it was with or without bolts.

[Thoglan]

Yeah, I have no idea what bolts to order when I do mine. Mine is an 03, pre-LCI, but had the RB recall done in 05.

Recall shouldn't really change anything, nor is it tied to the facelift models. My guess is you have the later bolts as I remember being told the changeover happened early 2002, can't confirm though. Truthfully you probably won't know 100% until you open it up.

[BMWahba]

Yeah, I have no idea what bolts to order when I do mine. Mine is an 03, pre-LCI, but had the RB recall done in 05.

[Slideways]

Here are ARPs recommendations for reusing their bolts:

"Are ARP bolts and studs re-usable?

Yes. As long as the fasteners have been installed and torqued correctly, and show no visible signs of damage, they can be re-used. If they show any signs of thread galling or corrosion, they should be replaced. In the case of rod bolts, if any of them have taken a permanent set and have stretched by .001” or longer, you should replace them immediately. See page 29 in the catalog for more detailed information on this critical measurement."

I assume the same applies for the stock M11s. Unfortunately, we don't have access to new stock M11 bolts, but if someone wanted to take a used bolt and measure it before and after and do that multiple times, then we might have a better idea of how many times they can be reused (not taking into account heat cycles). At some point, maybe around 3 since that sounds like a good number, I'd most likely replace the stock M11s for the ARP M11s as Lang Racing posted that they do not distort the bore unlike the ARP M10s.

[Tbonem3]

Ya that's true, didn't even think of that. I saw it while looking at Turner's description for ARP bolts. Maybe they meant new M11. Which is even better as that's 1 less use to worry about.

[heinzboehmer]

Also, it sounds like some of the pre 2003 cars, when they had the recall done, had m10 bolts used, not the original m11. So I guess you have to open her up before you'd know if you can reuse the bolts or if you need to buy new ones.

That doesn't sound right. An M10 bolt won't fit on M11 threads. The whole rod would have had to be changed for this to happen, which is definitely out of scope for the rod bearing service bulletin.

The bulletin says the switch from M11 to M10 happened on 12/13/2002. However, the bulletin applied to cars produced up to 05/22/2003, so there are five months worth of cars that both got the M10 bolts from the factory and got the bearings replaced under the bulletin. Maybe that's why some people have found M10 bolts when they were expecting the M11.

As for how many times the bolts can be reused, I guess theoretically the answer is an infinite number of times. As Thoglan said, the M11 bolts must not be torque to yield. As long as a bolt doesn't undergo plastic deformation, it should spring back to the same geometry it had when new. There's no way BMW paid for all these replacements but also decided to risk future engine failure (that would have been 100% their fault) by reusing a critical fastner that shouldn't have been reused.

In practice, the bolts can't actually be reused forever. But assuming that every time they're reused they're torqued as close to spec as possible, I personally wouldn't worry about reusing them for the life of the engine (but I'm not qualified to be giving out advice, so take this with a grain of salt). They'll probably be reused five times max?
Regardless, I haven't been able to find a place that sells the M11 bolts by themselves, so it looks like you're stuck reusing them anyway (unless you go for ARP).

[Tbonem3]

So can you use original m11 2 times? 3 times? Infinite?

Also, it sounds like some of the pre 2003 cars, when they had the recall done, had m10 bolts used, not the original m11. So I guess you have to open her up before you'd know if you can reuse the bolts or if you need to buy new ones.