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      12-07-2019, 08:14 AM   #1
Reborn_
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ZHP Control Arms

I tried searching and other than a few sparse comments about people buying these because they are better, I have not found out why. Can someone comment on what advantage, if any, the ZHP control arms have over standard Z4M ones? Going to be buying new ones for the ball joints and ZHP is only ~$40 more per side, so if there is a real advantage, why not.


EDIT:
Based on part #s, ZHP is the standard Z4M OEM control arm.

Real OEM shows Z4M part numbers as:
left control arm 31122341297
right control arm 31122341828

Based on the language in the ECS postings and what Guido posted, I'm surmising that ball joints in the Z4M and Z4 with Performance Package are 'upgraded' relative to Z4 without the Performance Package. Includes the upgraded ball joints from the Performance Package

ZHP Left

ZHP Right

Last edited by Reborn_; 12-07-2019 at 07:25 PM.. Reason: question answered
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      12-07-2019, 09:47 AM   #2
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these the oem arms? if so, I doubt there is much difference between the run of the mill sets. They are made to spec, maybe if someone knows different, hopefully they will chime in.
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      12-07-2019, 10:45 AM   #3
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Quote:
Originally Posted by Reborn_ View Post
I tried searching and other than a few sparse comments about people buying these because they are better, I have not found out why. Can someone comment on what advantage, if any, the ZCP control arms have over standard ones? Going to be buying new ones for the ball joints and ZCP is only ~$40 more per side, so if there is a real advantage, why not.
ZCP arms are afaik the same as the z4m control arms? They have the same partnumbers if I look them up.

On the german Z forum there has been a fairly extensive study between the z4m arms and normal arms (like from the 3.0i) and as far as measurements go, there aren't any.
Speculated is that the ball joints on the z4m arm are stronger (they may have a different plastic liner inbetween), but they don't handle differently. They just may last longer.
As the z4m has both more caster and a slightly wider stance due to different wheel/flange offset (so larger scrub radius I presume), the forces on the control arms are higher too.
That would be a reason to beef up the balljoints.
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Last edited by GuidoK; 12-07-2019 at 10:54 AM..
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      12-07-2019, 11:13 AM   #4
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I was trying to figure out this myself earlier this year and decided to go with Meyle Heavy Duty Lower Control Arm Assembly for left and right. They came with a 4 year warranty and serviceable all-metal ball joints!

And I also wanted a better option for my control arm bushings instead of the soft OEM bushings and went with Turner Motorsport 80A Polyurethane Front Control Arm Bushings with pre-Installed brackets.
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      12-07-2019, 07:17 PM   #5
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I should have clarified for the Z4M. I am embarassed to say I didn't even think to check part numbers - it looks like Guido is right, part numbers show oem equipped arms for the Z4M are "ZHP." First post updated.

Last edited by Reborn_; 12-07-2019 at 07:23 PM..
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      12-10-2019, 04:00 PM   #6
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Back in the day, the story on the E46 ZHP control arms, relative to regular E46 control arms, was ball joints are stiffer for better steering feel. Same part #s as Z4m parts.
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