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Old 08-23-2005, 06:59 PM   #1
zuczek
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Default aluminium control arm differences

I was searching but could not find a definite ansewer.

What are the differences between:

1. USDM Sti Control arms
2. JDM Sti V7 Control arms
3. JDM Sti V8 Control arms
4. JDM Sti Spec-C Control arms

Which will give you more caster when installed on a 02 USDM WRX Sedan. Also, is there a difference in the transverse links on them?


How to identify the control arms from each other? Markings? Part Numbers? Cutouts etc...
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Last edited by zuczek; 08-24-2005 at 05:06 PM.
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Old 08-24-2005, 02:19 AM   #2
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Bump for answers
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Old 08-24-2005, 03:03 AM   #3
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bump too.


not to hijack, but what are the tangible differences in performace to those that have them?
does it change the way the car feels?
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Old 08-24-2005, 09:48 AM   #4
advanracing62
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I know that the control arms are definately less unsprung weight. As we all know unsprung weight adds signifigant value to perfomance both motor and suspension. I have been looking at the Alumininum control arms for a bit now, but am wondering if there is a way to install pillowball mounts in place of the bushings.. and then I'll be adding Moog ball joints to the combo.
As far as differences in versions.. well I have no clue. BIGSKYWRX should chime in and advise us.
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Old 08-24-2005, 05:06 PM   #5
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bump for more info
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Old 08-24-2005, 05:34 PM   #6
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are there even differences between the aluminium control arms, i thought they were all the same.
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Old 08-24-2005, 09:34 PM   #7
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ver.7-8 wrx sti non-spec c/ra's are just forged aluminum, same design aspects as stamped steel US, non sti imprezas. The ver.8-9 spec c/ra are different design that pushes the strut forward to add more positive castor (similar to adding an anti lift kit). that should be right
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Old 08-24-2005, 09:42 PM   #8
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The 04 USDM STi has the same caster/wheelbase as the 2003 JDM Spec-C,the standard JDM STi did not share the same specs. The newer crosseyed JDM STi, spec'd like our 05 STi bumped up to those settings so I'm thinking that perhaps they all share the same control arm or they all have some sort of offset control arm pivot mount.
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Old 08-24-2005, 10:17 PM   #9
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If you had all of the different mounts laying on a table, how would you be able to tell which one is which?
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Old 08-24-2005, 11:59 PM   #10
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v7 are different, v8 USDM/JDM/Spec C are the same. The v8 ones do offer additional caster (~ 1.5 degrees)- how this is accomplished has never been answered very well. I do know the v8 utilize a different rear bushing, as well as utilzing a different cross member. How and if they contribute to the caster change I'm not sure.

I do know there are subtle appearance differences between the GC aluminum arms and the v7's (length and shape of voids)- I'd venture a guess there are subtle appearance differences betwen v7 and v8 as well- unfortunately I've never seen them side by side.

Here's a pic of the v7 one

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Old 08-25-2005, 02:30 AM   #11
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BIGSKYWRX - Is there any markings on the V7 cointrol arms?? Any codes? Paint dots etc?? Is it for sure that the regular JDM V8 Sti (Non-Spec C) will have the extra caster as well when installed on a 02 WRX??

Here is a picture of what I just got and was told it was from a JDM V8 STI.





Does any one have a DATA SHEET with the wheelbase specifications for a V8 JDM Sti showing the wheelbase of the regular Sti and well as the Spec C??

Last edited by zuczek; 08-25-2005 at 02:36 AM.
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Old 08-25-2005, 06:16 AM   #12
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I found a data sheet a couple of years ago but I think the site no longer exists.

Found it

http://www.japanvehicles.com/newcars...X2004/main.htm
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Old 08-25-2005, 09:50 AM   #13
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All I know is that they're much stiffer, structurally, than OE. So much so that a lot of rally drivers don't actually want them... They're so stiff, that impact doesn't collapse the control arm, it bends at the frame instead.

Subie Gal I think has the same issue... I'm sure they have tremendous benefits, but for a low or moderate racing budget, maybe not a good idea? At least from what I've read. Don't shoot the messenger.

=S2=
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Old 08-25-2005, 10:21 AM   #14
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If you look carefully the one you have pictured looks different (unles it's flipped over- take a pic from the other side as well if you could)- which would lend credibility that it is indeed a v8 one.

The aluminum ones are indeed stiffer, that's the primary reason they use them (it's like a large bushing in effect- les deflection w/ the aluminum)- the weight difference is very neglible- the al arms are only 3/4 lb lighter/side. You do run a possible risk in a front end accident to do more damage to the suspension as the aluminum one won't crumple as readily as the steel one. Also remember that the rest of the world has been running these aluminum arms as oe on all WRX's and STi's for several years. North America is the only market I'm aware of that doesn't get these arms- and that may possibly change w/ the 06 (rumor )
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Old 08-25-2005, 01:54 PM   #15
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Couple more pics. I think it looks the same except maybe this area.








Does anyone have a picture of the USDM Sti or Spec C Control arm??
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Old 08-25-2005, 02:03 PM   #16
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Well, I guess it clearly shows here that in a JDM 2005 ONLY the Spec-C has the 2540mm wheelbase and everyone else gets the 2525mm. So I guess it means that the V7 and V8 control arms (Non Spec-C) are the same dimensions.



Quote:
Originally Posted by supermarkus
I found a data sheet a couple of years ago but I think the site no longer exists.

Found it

http://www.japanvehicles.com/newcars...X2004/main.htm
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Old 08-25-2005, 02:24 PM   #17
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Quote:
Originally Posted by zuczek
Well, I guess it clearly shows here that in a JDM 2005 ONLY the Spec-C has the 2540mm wheelbase and everyone else gets the 2525mm. So I guess it means that the V7 and V8 control arms (Non Spec-C) are the same dimensions.
. so can anyone verify if there are any different markings vs ver.7-8 non spec-c and ver.8-9 spec-c? i didn't notice any on my ver.7 arms.
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Old 08-25-2005, 04:40 PM   #18
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here is the control arm from a ver 8 spec c control arm

image from rallispec
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Old 08-25-2005, 04:56 PM   #19
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Quote:
Originally Posted by DaFastOne
here is the control arm from a ver 8 spec c control arm

image from rallispec
Actually if you look at the suspension products page that the image comes from it says Legacy arm pictured.

Quote:
Originally Posted by RalliSpec
RST-2000kit Standard Kit Impreza MY02+ $384
RST-2002kit Spec C Kit Impreza MY02+ $657
RST-2001kit Impreza MY93-01 $1018
RSTF-199kit Forester MY04+ $708
RST-200L Legacy MY05+ $708
Forged aluminum control arms reduce unsprung weight. Spec C kit for New Age Impreza sedan models also alters front suspension geometry by increasing caster angle. This benefits cornering grip by providing more dynamic negative camber. All kits except GC/GF kit includes LH & RH complete assembled control arms. Impreza GC/GF kit includes LH & RH arms, ball joint cones, metal front swaybar links, and rear bush washers. Note that US STi comes standard with RST-2020kit from the factory. Legacy arm pictured.
Assuming the "RST-2020" is a typo then RalliSpec are saying that the USDM STi has the increased caster version the same as the Spec C.
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Old 08-25-2005, 05:45 PM   #20
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Someone must have a USDM control arm to take picture of.
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Old 08-25-2005, 06:36 PM   #21
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I see a couple of differences in the pic- look at where the sway link attaches the v7 has a little bit that protrudes into the arm- yours doesn't. Also look where the rear bushing mounts- yours shows a small void where there is none in the v7 one.

All of the v8 STi's receive the additional caster.

Would be nice to see a pic of a "confirmed" USDM one
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Old 08-25-2005, 09:14 PM   #22
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hmm, looks to be one complete piece w/ tranverse link. i'll take a look at my friends 05 sti and see if its the same.
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Old 08-25-2005, 10:15 PM   #23
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I've held the V7 control arms and the stock stamped-steel control arms in my hands and on a scale; they're within a pound of each other.

The biggest benefit comes from the siffter transverse link bushing on the V7 control arms which is why folks say it feels so different after changing them.

Personally I'd buy the Group N transverse link bushing and go with that rather than pay the expense and go through the hassle of swapping the whole control arm.

Not to mention that they are a bit stiffer and thus rally drivers don't tend to use them as they don't have a built-in failure point.

While reducing unsprung weight is never a bad thing it's honestly not significant in most cases of a street car and unless the car is relegated to racing-only duty I would basically never give them another thought. The biggest percentage of gain is in the bushings; the stamped steel is quite strong on it's own.

-Biggly
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Old 08-25-2005, 10:34 PM   #24
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Can someone provide the part numbers of the various AL control arms?
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Old 10-20-2005, 08:23 PM   #25
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A quick question here. Are the suspension pick up points all the same on all MY's of USDM WRX's? Meaning, would I be able to put V8's on an '02 or '03?

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