OEM Suspension Bolts

[t3ddftw]

Hey guys,

I'm going to be replacing all suspension bolts on a new project pretty soon and I'm wondering if anyone knows what the OE bolts are coated with from the factory? Or, are they even coated? My untrained eye thinks they're hot dipped galvanized, but if they were I suspect they would deal with corrosion a little better than they actually do.

In the end, I'm looking to send them off somewhere to get the most corrosion resistant coating applied.

-Ted

[cobra]

Why not just buy the OEM bolts? They hold up pretty damn well.

They appear to be zinc coated, which is one of the best anti-corrosion coatings possible. You can buy Zinc-Aluminum coated bolts on McMaster.

[t3ddftw]

Why not just buy the OEM bolts? They hold up pretty damn well.

They appear to be zinc coated, which is one of the best anti-corrosion coatings possible. You can buy Zinc-Aluminum coated bolts on McMaster.

The plan is to buy all new OEM bolts and then have them re-coated if possible. I agree that they appear to have Zinc on them, but I don't know if it's hot dip, flake or something else I don't know about.

I was just looking at stainless steel bolts on McMaster, but I don't know that I necessarily want to source all new non-OEM bolts.

Unfortunately, I live somewhere with weather, and any kind of corrosion whatsoever is going to drive me nuts.

-Ted

[cobra]

The plan is to buy all new OEM bolts and then have them re-coated if possible. I agree that they appear to have Zinc on them, but I don't know if it's hot dip, flake or something else I don't know about.

I was just looking at stainless steel bolts on McMaster, but I don't know that I necessarily want to source all new non-OEM bolts.

Unfortunately, I live somewhere with weather, and any kind of corrosion whatsoever is going to drive me nuts.

-Ted

Stainless would be bad from galvanic corrosion and strength perspectives.

To me, the OEM bolts look like a combination of zinc-aluminum coated, and zinc flake depending on location.

If you buy them on FCP then you can just get free replacements whenever they start to rust

[George Hill]

Ted, I don't have the answers you are looking for, but I thought this was an interesting project. A quick search came up with this (and you may be further down the road than this, but I also want to now be subscribed to the post, lol):

https://www.realoem.com/bmw/enUS/showparts?id=BL93-USA-10-2002-E46-BMW-M3&diagId=31_0518

https://www.r3vlimited.com/board/forum/e30-technical-forums/general-technical/138891-bmw-nuts-bolts

https://holzapfel-group.com/en/surfaces/anti-corrosion-surfaces/zinc-nickel.html

And

https://www.bimmerforums.com/forum/showthread.php?2105878-BMW-Bolt-Codes

[t3ddftw]

Stainless would be bad from galvanic corrosion and strength perspectives.

To me, the OEM bolts look like a combination of zinc-aluminum coated, and zinc flake depending on location.

If you buy them on FCP then you can just get free replacements whenever they start to rust

Thanks! I didn't realize switching to stainless would cause issues with galvanic corrosion, so that rules that out!

Ted, I don't have the answers you are looking for, but I thought this was an interesting project. A quick search came up with this (and you may be further down the road than this, but I also want to now be subscribed to the post, lol):

https://www.realoem.com/bmw/enUS/sho...diagId=31_0518

https://www.r3vlimited.com/board/for...bmw-nuts-bolts

https://holzapfel-group.com/en/surfa...nc-nickel.html

And

https://www.bimmerforums.com/forum/s...BMW-Bolt-Codes

Thanks! I knew some of these abbreviations from RealOEM, but I hadn't run across these threads where some light was shed on them

FWIW, part of what sparked my interest in this idea was seeing someone who had their hardware yellow zinc (Zinc Chromate?) coated:


-Ted

[George Hill]

Maybe try reaching out to James Redish of Redish Motorsport, they do underside restorations and seem to always have new (or maybe refurbished hardware) in their builds

https://www.instagram.com/p/CYKfgO7qZhH/

[Arith2]

This explains why not to use galvanized bolts. Just because something is resistant to the elements doesn't mean it's resistant to what it sits against. Steel and galvanized bolts don't agree with each other. They should only touch aluminum.

https://pomametals.com/how-to-prevent-galvanic-corrosion/

[Ianb]

I used Geomet zinc flake coated bolts, not sure if factory bolts are but has the same silver/grey appearance and supposed to have good corrosion resistance.