Aluminum Control Arms?

E28 technical advice asked and given! Troubleshooting, modifications and more.
Walt
Posts: 303
Joined: Feb 12, 2006 12:00 PM
Location: Seattle

Post by Walt »

When I purchased my Suspension Techniques sway bars from him, I asked about the need for reinforcing the mounting points. He said he'd never seen any failures and that it wasn't necessary to do any reinforcing. Now, how many of us would agree with that?


Agreed, I don't think those S. Cal boys see the rough roads, or the track, as often as some of us.
He made good on it, but he's fallible, just like the rest of us


I'm not trying to make him out to be either a Guru or perfect. He's been fair, and mostly right with my transactions. I merely put him up as an experienced professional.

Now, if you guys could help me with a couple questions, I'd appreciate the education:
Despite the fact that ball joints are steel, and under normal conditions, in steel arms, the moving joint is the weak link, is it not possible that this steel unit, being pressed into an aluminum structure is vulnerable to aluminum erosion/compression/deflection and or wear? Whouldn't play in the ball joint allow for increasing pounding of the joint on the aluminum LCA?
Does anyone have a cross section of the ball joint?

Secondly, assuming you drop as much as a few pounds by replacing the steel arms, what tangible advantages are there for a) street or b) track?

Thanks,
Walt
shifty
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Location: Greenville, SC
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Post by shifty »

[QUOTE="Shawn D."]We all know that the "experts" can be fallible. While Carl Nelson is obviously a respected authority in BMW circles, a person can't be right about everything. When I purchased my Suspension Techniques sway bars from him, I asked about the need for reinforcing the mounting points. He said he'd never seen any failures and that it wasn't necessary to do any reinforcing. Now, how many of us would agree with that? :)[/QUOTE]

Oh shut up, Shawn. Yours didn't need reinforcing! ;)

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Shawn D.
Beamter
Beamter
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Post by Shawn D. »

[QUOTE="Walt"]Now, if you guys could help me with a couple questions, I'd appreciate the education:
Despite the fact that ball joints are steel, and under normal conditions, in steel arms, the moving joint is the weak link, is it not possible that this steel unit, being pressed into an aluminum structure is vulnerable to aluminum erosion/compression/deflection and or wear? Whouldn't play in the ball joint allow for increasing pounding of the joint on the aluminum LCA?

Does anyone have a cross section of the ball joint?[/QUOTE]

The ball joint assembly is indeed pressed into the arm, but the ball joint spherical section does not wear on the aluminum arm -- it wears on a mating seat. AFAIK, that seat is steel.
fastpat
Posts: 1036
Joined: Feb 12, 2006 12:00 PM
Location: Travelers Rest, South Carolina

Post by fastpat »

I've seen Shawn's repair of the rear stabilizer bar mounts, but not the front repair. Are there such photos and an accompanying article on it, perchance? :? :D
fastpat
Posts: 1036
Joined: Feb 12, 2006 12:00 PM
Location: Travelers Rest, South Carolina

Post by fastpat »

[QUOTE="Walt"]Now, if you guys could help me with a couple questions, I'd appreciate the education:
Despite the fact that ball joints are steel, and under normal conditions, in steel arms, the moving joint is the weak link, is it not possible that this steel unit, being pressed into an aluminum structure is vulnerable to aluminum erosion/compression/deflection and or wear? Whouldn't play in the ball joint allow for increasing pounding of the joint on the aluminum LCA?

Does anyone have a cross section of the ball joint?[/QUOTE]

[QUOTE="Shawn D."]The ball joint assembly is indeed pressed into the arm, but the ball joint spherical section does not wear on the aluminum arm -- it wears on a mating seat. AFAIK, that seat is steel.[/QUOTE]

Yes, and the exterior of the ball joint is plated with yellow zinc as a sacrificial coating. by the time the zinc has moved, the ball joint is needing replacement I'd guess. ;)
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