Bmw OE parts “quality” main bearing content

[Slideways]

Ok, so round two.

For the life of me couldn’t figure out why I couldn’t get the thrust bearing in spec. Turns out, it’s messed up, too.

pretty large machining error that left a sizable lip.

another day, another return to zee Germans. PSA to check your bearings very carefully!

Oof, if only you could return all the main bearings and see if the ACL bearings are a better option. I believe Hack Engineering in the UK uses ACL main bearings on their rebuilds. IIRC, main bearings don't wear like rod bearings do on the S54.

[tlow98]

Oof, if only you could return all the main bearings and see if the ACL bearings are a better option. I believe Hack Engineering in the UK uses ACL main bearings on their rebuilds. IIRC, main bearings don't wear like rod bearings do on the S54.

I started with the ACLs from Hack. Overall, they are great. The issue is that you can’t get them in .006mm differing sizes like the BMW bearings. So, I ended up with varying clearances that, while maybe were acceptable, where not the way it left the factory. Two mains were just out of spec according to BMW with the ACLs. Would it have been ok? Likely, but it was causing me to lose sleep on a motor that already has pretty low oil pressure.

The ACLs were in better shape when they arrived. None of the manufacturing issues I’m seeing with the BMW bearings. If you have a perfectly uniform crank then the ACLs should work great.

if you’re seeking the smallest variance across the mains you’ll need to mix/match sizes with the BMW OE main bearings. Apparently, tho, you’ll have to order a bunch of extras, because they’re rather a bit garbage.

[Syfon]

You can fix the thrust bearing yourself?

I've ACL rod & main bearings in mine. The thrust bearing was too thick by a decent amount; I used a piece of glass & emery paper (with water) and sanded either side till it had the correct clearance.

As for the damaged main bearing in your op, it will be fine.

When i disassembled my s54 due to a spun rod bearing, one of the crank main bearings has two decent chunks taken from it, however the corresponding crank main journal showed zero damage.

The main journals just spin around inside the bearings on the same plane, unlike the rod bearings which take a beating (relatively speaking ofc)

[tlow98]

You can fix the thrust bearing yourself?

I've ACL rod & main bearings in mine. The thrust bearing was too thick by a decent amount; I used a piece of glass & emery paper (with water) and sanded either side till it had the correct clearance.

As for the damaged main bearing in your op, it will be fine.

When i disassembled my s54 due to a spun rod bearing, one of the crank main bearings has two decent chunks taken from it, however the corresponding crank main journal showed zero damage.

The main journals just spin around inside the bearings on the same plane, unlike the rod bearings which take a beating (relatively speaking ofc)

Thanks for weighing. My ACL was spot on for axial clearance. This OE thrust bearing has pretty decent portion of the thrust bearing incorrectly removed and lots of nasty edges along with it. It’s hard to make out in the pics, but I’m not going to trust it.

overall, I’m a little shocked the OE bearings came so beat up and the ACLs seemed perfect. Kudos to ACL!

[Syfon]

Thanks for weighing. My ACL was spot on for axial clearance. This OE thrust bearing has pretty decent portion of the thrust bearing incorrectly removed and lots of nasty edges along with it. It’s hard to make out in the pics, but I’m not going to trust it.

overall, I’m a little shocked the OE bearings came so beat up and the ACLs seemed perfect. Kudos to ACL!

Sorry my misunderstanding - I thought you were referring to the axial clearance haha.

Yeah that definitely doesn't sound right for OE bearings to not be in (effectively) perfect condition.

Hope you get it sorted and running in good time

[bmw m3 s50]

I just ordered a set of rod bearings from FCP euro, along with tons of other parts. They ended up throwing everything in one box with a couple of air bags for cushioning which did nothing. When box arrived it was armageddon. The boxes holding the rod bearings were crushed. FCP Euro having superior customer service ended up just shipping me a new set of rod bearings. I am curious to know, how easy it is to damage the rod bearing if something heavy is placed on it or if it is banged around during shipping.

[tlow98]

I just ordered a set of rod bearings from FCP euro, along with tons of other parts. They ended up throwing everything in one box with a couple of air bags for cushioning which did nothing. When box arrived it was armageddon. The boxes holding the rod bearings were crushed. FCP Euro having superior customer service ended up just shipping me a new set of rod bearings. I am curious to know, how easy it is to damage the rod bearing if something heavy is placed on it or if it is banged around during shipping.

my packages arrived in perfect order with great packaging. I would trust anything in your state of affairs. It doesn’t take much to tweak a bearing dimensionally. For sure, send it all
back. Sorry to hear!

[bmw m3 s50]

my packages arrived in perfect order with great packaging. I would trust anything in your state of affairs. It doesn’t take much to tweak a bearing dimensionally. For sure, send it all
back. Sorry to hear!

They ended up sending me a complete replacement set, so that is not an issue. Just curious to know how fragile these rod bearings could be.

[tlow98]

They ended up sending me a complete replacement set, so that is not an issue. Just curious to know how fragile these rod bearings could be.

well, you can deflect them with your hand, and the tolerance is extremely tight. So, my scientific answer is, “pretty fragile” :-)

[bmw m3 s50]

well, you can deflect them with your hand, and the tolerance is extremely tight. So, my scientific answer is, “pretty fragile” :-)

Wow, makes doing the rod bearings even more nerve racking.

[tlow98]

Wow, makes doing the rod bearings even more nerve racking.

nah, you’ll be alright. Just don’t drop them and wear clean gloves! Should be fine if you take your time and work carefully.

[Pklauser]

I just ordered a set of rod bearings from FCP euro, along with tons of other parts. They ended up throwing everything in one box with a couple of air bags for cushioning which did nothing. When box arrived it was armageddon. The boxes holding the rod bearings were crushed. FCP Euro having superior customer service ended up just shipping me a new set of rod bearings. I am curious to know, how easy it is to damage the rod bearing if something heavy is placed on it or if it is banged around during shipping.

Yea I had a similar experience. I've learned to order them on their own from now on.