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Old 05-27-2022, 09:21 PM   #71
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I'm curious about the 1st gen LCA too. I think I'll wait until all this stuff gets ironed out before doing any suspension mods.
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Old 05-30-2022, 05:30 PM   #72
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Originally Posted by Xed32 View Post
'22 BRZ Question. I see most persons using the Gen1 rear LCA and coilovers. We know the '22 RLCA is around 0.5" different: https://www.ft86club.com/forums/show...54#post3495854

How does that affect the motion ratio? Additionally, the track between Gen 1 and 2 is different (staggered)? It appears most suspension offerings for Gen2 are the Gen1 parts and spring rates. Should this matter?
Additionally, the MCA traction mod ( best mod i've ever put on a car) really tames the rear end step-out and adds comfort. It does not affect alignment, but does changing the anti-squat characteristics affect motion ration at all? I do feel like I can get away with much higher rear spring rates now that the rear end is predictable. I am currently on stock suspension but am looking for performance oriented suspension parts for track and auto-X and most of what I find is looks oriented.
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I'm curious about the 1st gen LCA too. I think I'll wait until all this stuff gets ironed out before doing any suspension mods.
I wrote up this little discussion of the 1st vs 2nd gen differences:
https://www.racecompengineering.com/...ension-changes

Rear motion ratio is a tiny bit higher with the 2nd gen. The example I gave in the article is that a 300 lbs/in rear spring would be about 10 lbs/in stiffer in wheel rate on 2nd gen compared to 1st gen. Not huge, but it's there. Then there's the slightly increased track width in the rear that works against that.

One thing that's interesting is that most 1st gen adjustable rear LCAs actually already have the 2nd gen geometry. This is because the 2nd gen BRZ rear LCAs are the same part number as they are Subaru VA chassis (2015-2021 WRX and STI) and many aftermarket companies have been using the same LCAs for both 1st gen BRZ, VA chassis, and a whole bunch of other Subarus (for better or worse). The act of adjusting the LCAs changes the motion ratio a tiny bit anyway. For me it's not a large concern. I do not expect anyone to make an adjustable 2nd gen specific rear lower control arm, but I'm not in the rear lower control arm business.

The MCA traction mod should not affect motion ratio as far as I'm aware.

- Andrew
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Old 06-03-2022, 10:20 PM   #73
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One thing that's interesting is that most 1st gen adjustable rear LCAs actually already have the 2nd gen geometry. This is because the 2nd gen BRZ rear LCAs are the same part number as they are Subaru VA chassis (2015-2021 WRX and STI) and many aftermarket companies have been using the same LCAs for both 1st gen BRZ, VA chassis, and a whole bunch of other Subarus (for better or worse).
Interesting, which adjustable gen1 arms actually use the gen2 geometry?
I know Verus isn't one of them.
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Old 06-10-2022, 08:52 AM   #74
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Interesting, which adjustable gen1 arms actually use the gen2 geometry?
I know Verus isn't one of them.
It's hard to tell, but my guess is most (not all) that are listed as for 2008 to 2020 WRX/STI in addition to BRZ were originally developed for the WRX/STI.

Gets complicated with the arms that have multiple mounting holes and the Cuscos that have 2 position mounting key thing.

Again the difference is small and when you adjust camber with the LCA it changes the length of the arm and the motion ratio slightly anyway.

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Old 06-10-2022, 02:26 PM   #75
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Again the difference is small and when you adjust camber with the LCA it changes the length of the arm and the motion ratio slightly anyway.
Totally!
I'm more worried about legality in the autox STR class than motion ratios at this point though.

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It's hard to tell, but my guess is most (not all) that are listed as for 2008 to 2020 WRX/STI in addition to BRZ were originally developed for the WRX/STI.
If you ever confirm, please share!
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Old 07-05-2022, 10:01 PM   #76
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If anyone is curious.
2013-2020 BRZ (2013-2014 wrx & STI) RLCA part#20250FG042.
2022 BRZ (2015-2017 WRX & STI) RLCA part #20250AL011.
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Old 07-06-2022, 10:05 AM   #77
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Originally Posted by timurrrr View Post
Interesting, which adjustable gen1 arms actually use the gen2 geometry?
I know Verus isn't one of them.
The Verus 7000 series LCA's are listed as fitting 2008-2021 WRX/STI in addition to the BRZ/FRS/86, so maybe they can accommodate the 2nd gen geometry as well?
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Old 07-08-2022, 02:56 PM   #78
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The Verus 7000 series LCA's are listed as fitting 2008-2021 WRX/STI in addition to the BRZ/FRS/86, so maybe they can accommodate the 2nd gen geometry as well?
"Accomodate" is not the same as "use".
You can find my posts on this forum where I measure these Verus arms and they don't match the geometry of gen2 cars, and thus are not legal in SCCA STR.
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