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Discussion Starter #1 (Edited)
I have a 1994 E34 3.8 M5 Touring. Can anyone confirm the original material for each of the upper control arms, and the lower control arms, ie: aluminum or steel. My shop says I have steel on the lower and that they should be aluminum, but just wanted to confirm before changing.

Are the upper control arms also called thrust arms and have the large bushing that has to be tightened with the car on the ground? Are the lower control arms also referred to as wishbones?. I've seen different terminology thrown around, and wanted to get clarification.

Also, I have read that there may be a replacement (lower control arm) from an E31 that has spherical bearings, rather than bushings (p/n's 31-12-1-138-477, 31-12-1-138-478). Has anyone done this and is it recommended?
 

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Upper control arms are always steel (these are also called thrust arms, and have the large bushing). Lower arms are aluminium on earlier 3.8s, but 6 speeders with 18" wheels had steel lower arms. Personally I am going to try the E31 lower controls arms soon my self (these are aluminium with a spherical bearing).

Alex
 

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Discussion Starter #4 (Edited)
Alex, I have the Nürburgring package (if I am calling it by its correct name) with the 6 speed and 18 inch Parallells, so I guess it is correct mine are steel. Do you think they may be steel on these cars because it is needed for strength vs. the aluminum?

I wonder if the E31 spherical bearing arms are strong enough for the forces with the bigger/wider wheels (assuming they are in aluminum,) or if these E31 spherical bearing arms are available in steel...
 

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Richard,
the bushing side of the arms must be tightened with the suspension weighted to make sure the bushing can flex equally in both directions. Otherwise, they would already be fully flexed once the car is lowered, and any more movement would quickly destroy the bushing.


I reckon the e31 arms will hold up well since that car came with v12 engines and
the same heavy big brakes that the 6 speed M5 did.
 

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Went with the E31 aluminum spherical bearing lower control arms, in place of the factory steel units. Shall see how they do...

...I'm watching this space keenly.....I need a couple of arms too and was also wondering about the E31 type...

Anyone out there with long term E31 arm experience ?
 

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thinking of doing this myself. Did a search, limited feed back, anyone else out there with any good or bad to report?
 

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Spherical bearing should be more durable in theory.
No data that I know of to support longer overall durability though.
Trouble is, its a wishbone connected at both ends.
It won't stop the lower control arm outer balljoint from wearing.

Someone out there will tell me you can pull & press these back in.
Ally arm = never.
Steel = let me know when you are going to attempt this & I will come
round, pull up chair & watch the show ;)

Buy O/E steel control arms...
Drive them & kill bushes.
Drill them out ( if ally) & fit Powerflex black.
Drive some more...& kill the outer balljoints.
Remove the arm, keep the PF bushes.
Fit PF black to new control arm =
The cycle of lower control arm life:)

Errr. right, parts arrived, off to work
Cheers
 

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I somehow figured that this would be the "ultimate formula " .

Thanks for articulating it......now we know for sure which direction follow !

BTW...Faz pull over 2 chairs 'cause pulling a ball joint is going to be one heck of an interesting show.....I'll even cross the "pond" to watch that one and see the poor bloke who will drive the car. ( Actually, I'll warn him not to risk his life since we're all "passionate brothers " on here ! )

I experimented on this in my school days and it never worked.

The metal ball and socket were always compromised once the ball had been removed from the socket......it may work for some time all right but on the day you're up for enthusiastic driving and you've forgotten that you're driving on a compromised system.....that's when it gives way....and without warning too!

Try hitting a bump/pot hole at speeds over 150km/h with this set-up.......If you remember you gotta ask yourself one question.... " Do I feel lucky ?.....Well do ya punk ?

Cheers
 
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