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Old 07-04-2004, 11:09 AM   #1
BIGSKYWRX
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Default How EXACTLY does the STi gain it's ~ 1 degree of caster

Does anyone know exactly how they gained the additional degree? I see the rear transverse bushings have different part#'s

WRX (R) 20201FA070
(L) 20201FE080
STi (R) 20204FE110
(L) 20204FE120

Are the metal portion of the bushings thicker on one side ala Whiteline ALK (I don't think so as there are no spacers on the subframe- as needed w/ the ALK)?

Are the bushing holes offset? Is the entire cross member mounted differently to allow for more caster? Is the black piece that holds the rear bushing a different shape than the one that came w/ the v7 aluminum arms?

Inquiring minds want to know.

Thanks

Big Sky
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Old 07-04-2004, 01:04 PM   #2
Uncle Scotty
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I remember reading in a post somewhere that it was a combination of things but I believe most of it is due to the transverse link(aka 'control arm') being dimensionally a bit different in such a way as to add caster, and this was one of the lesser known benefits of the aluminum 'control arms'.

Whether this is, indeed, factual or not, I don't know.
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Old 07-04-2004, 01:41 PM   #3
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The actual v8 arms are 20202FE300 and 310, the part # for v7 arms are a ST part# and include the entire assembly- both arms, rear bushings/ball joint etc. So I can't tell if the arms themselves are the same.

It's possible the actual arms are different, but it would be cheaper to reuse the same arms and tweak the rear bushing some how.

If it's just the rear bushing, might be a good option for guys running the v7 aluminum arms wanting another degree of caster.

Big Sky
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Old 07-04-2004, 01:50 PM   #4
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...if I wanted even more caster, I'd do the Whiteline bushes anyway, if the stock ones looked like they weren't offset.
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Old 07-04-2004, 02:48 PM   #5
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someone I know pretty familiar with subarus said its the control arms. The v7 and v8 ones are different because the v8 ones have more caster.

Peter
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Old 07-04-2004, 02:53 PM   #6
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Quote:
Originally posted by petawabit
someone I know pretty familiar with subarus said its the control arms. The v7 and v8 ones are different because the v8 ones have more caster.

Peter
Interesting- I'd love to see a set side by side and see what they did (if indeed the arms are different)
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Old 07-04-2004, 05:45 PM   #7
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The V8 sti's wheelbase is 100" versus, IIRC 99.4 for the V7. The extra .6 inches is due to the control arms which give the additional castor. Check out this thread
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Old 07-04-2004, 06:02 PM   #8
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Thanks- read that thread, still doesn't answer how the increased caster (and resultant whel base increase) was had. If it's the rear bushings vs the actual arm, it could be quite a boon for those w/ aluminum arms.

Big Sky
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Old 07-04-2004, 06:25 PM   #9
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bigsky-my friend was telling me the additional caster comes from the control arm itself, not from the bushing. Is it caster or castor? I don't want to be spelling it wrong this whole time. With kits such as the perrin and whiteline bits, I think it adds even more caster/castor to STi's.

Peter

OT-whats with the change bigsky? why did you leave the bugeyes for the wagon? :-) just wondering
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Old 07-04-2004, 08:32 PM   #10
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If it's the arms, I'd love to see what they've changed, from pics they look the same- but tough to get detail out of a pic.

Caster- castor = beaver or castor bean

I burnt the exhaust valves in my sedan, when I took it to the dealer- they made a deal I couldn't refuse - besides ever since my wife had founf out that the WRX was available as a wagon- that's what she really wanted.

Big Sky
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Old 07-04-2004, 09:16 PM   #11
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Quote:
Originally posted by BIGSKYWRX
Thanks- read that thread, still doesn't answer how the increased caster (and resultant whel base increase) was had. If it's the rear bushings vs the actual arm, it could be quite a boon for those w/ aluminum arms.

Big Sky
Ok smartypants read this thread , near the bottom of it you'll see rallispec's response to my questions about this "igalwrx: Since we've never held this part in our hands, it is impossible to say if it's a straight swap. However, it is uber-likely that they do bolt right on since the rear bushings are interchangeble. However (ver.2), the Spec.C and USDM STi share a rear bushing that doesn't have the same part# as all the other car's rear bushings, yet they are physically interchangeble. Confused? The jist is: if you're going to use these arms, also use the rear bushings that go along with them to aleviate any chance of wierd handling."
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Old 07-04-2004, 10:06 PM   #12
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I am relatively new to the WRX world.

Is the Caster on this car not adjustable by any other means than by changing a suspension part out for a differen't one? All my previous cars have had adj caster. Maybe that's abnormal, but I was hoping this would be the same way. I was going to get my STi re-aligned with slightly more neg caster and little more neg camber front with a proportionally smaller neg camber increase in the rear. However, if I can't adjust the caster I might just wait.
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Old 07-04-2004, 10:11 PM   #13
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Quote:
Originally posted by BHawk
I am relatively new to the WRX world.

Is the Caster on this car not adjustable by any other means than by changing a suspension part out for a differen't one? All my previous cars have had adj caster. Maybe that's abnormal, but I was hoping this would be the same way. I was going to get my STi re-aligned with slightly more neg caster and little more neg camber front with a proportionally smaller neg camber increase in the rear. However, if I can't adjust the caster I might just wait.
Increasing positive static caster in the Impreza is your friend

And the only way to change it is by changing parts, or hitting something...not recommended
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Old 07-04-2004, 11:17 PM   #14
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igalwrx- thanks for searching , but still doesn't answer the question. It has unique rear bushings ie as I posted above and they've never had one in their hands- I most have been from Missouri in a past life . I originally talked to Dave at rallispec, many moons ago when the revision c's were first coming out- he thought it was the rear bushings that gave the additional caster, he also thought the black piece that bolts onto the arm (don't know what to call the little bastard) was different as well.

BHawk- you have no worries, you've got the STi and 4.5 degrees of caster

Big Sky
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