Effect of Front Unsprung Weight Reduction?

[Tcoat]

Originally Posted by ML

they are about 400$ from subaru. Marsh is backed up over a year on carbon ones, and with my roll cage about to go in and having a dented roof I'm thinking about doing it.

May be worth while in that case then.

[Jianlun]

Originally Posted by Jianlun

This is a very informative page. Shows the ins and outs of a 2022 BRZ knuckle swap into a last gen (and i assume applies to the 2022 GR86 wholesale also).

https://minkara.carview.co.jp/smart/...4954/note.aspx

You would need to run Google Translate etc. Says some bolts need to change due to longer lengths needed for the alu knuckle. But also an interesting problem about the outboard ball joint (not possible to buy separately) of the FLCA being not long enough. Maybe thats the reason for the diff part number rather than any geometry changes?

Wonder if an (even lighter....) aftermarket FLCA (cusco, SPL, racerX) can fit the alu knuckles instead. Since the stock FLCA cannot plug and play per se. What the writer did was get a toyota castle nut which is thinner where it counts to allow the pin to successfully engage still.

If there ever was a doubt. I cross referenced the new GR86 FLCA with the previous gen and its the same.
https://parts.toyota.com/p/Toyota_20...U00310055.html
https://parts.toyota.com/p/Toyota_20...U00310056.html

So i guess the difference in part number for the 2022 brz vs the previous gen is due only to the ball joint being likely longer (and you cant buy that ball joint separately).

So i guess the question is whether the ball joint for the usual aftermarket FLCA fits the new alu knuckle. Anyone tried that?

EDIT: I emailed SPL and this is their reply:
We did redesign our ball joint stud for the FLCA FRS to fit the new 2022 BRZ, our FLCA FRS will fit your 2022 BRZ with alu knuckle!

[new2subaru]

Originally Posted by Tcoat

May be worth while in that case then.

Tcoat approved*

[Yoniyama]

Reducing front unsprung weight by 16lb is definitely worth the money and effort. I achieved similar weight saving by using a super-light wheel (Volks Racing TE-37 at 12.5lb each), 2-piece brake rotor (saving about 6lb each), light weight lug nuts, and hollow front sway bar.
The effect is noticeably positive on my 2018 BRZ. Of course the ride is much less jarring, and the steering feedback also improves. Now I can focus on the road ahead, rather than looking out for all the rough patch/pot hole to avoid.
I am now looking at replacing the front knuckle for another 3lb savings per corner.

[Rainy]

not trying to answer the question. it's great you can import RC trim from Japan, just wondering do you get air conditioning from RC trim this gen? I remember the 1st gen RC deleted basically everything like AC/speaker/sound deadening material/Catback exhaust etc. it's the lightest stock gr86 already, but the price increased by 800k yen IIRC

[Jianlun]

Originally Posted by Rainy

not trying to answer the question. it's great you can import RC trim from Japan, just wondering do you get air conditioning from RC trim this gen? I remember the 1st gen RC deleted basically everything like AC/speaker/sound deadening material/Catback exhaust etc. it's the lightest stock gr86 already, but the price increased by 800k yen IIRC

Yup, have Air con and LSD and ABS etc as the normal trims. But:
1. No Active sound
2. No head unit
3. Lesser underfloor sound insulation (havent found out which/where is less)
4. 16x6.5 steelies and 205/55r16
5. No trunk door liner and no trunk light.
6. No floor mats
7. Fabric seats, PVC for instrument cluster top and door cards. Leather steering and handbrake lever and gear knob.
8. 2 speakers (dashboard ones) only.
9. No wheel jacks
10. No cover on engine (the one that says D-4S Boxer).
11. No vanity mirror light, no puddle light.
12. No Cruise Control

[x808drifter]

Originally Posted by Jianlun

Yup, have Air con and LSD and ABS etc as the normal trims. But:
1. No Active sound
2. No head unit
3. Lesser underfloor sound insulation (havent found out which/where is less)
4. 16x6.5 steelies and 205/55r16
5. No trunk door liner and no trunk light.
6. No floor mats
7. Fabric seats, PVC for instrument cluster top and door cards. Leather steering and handbrake lever and gear knob.
8. 2 speakers (dashboard ones) only.
9. No wheel jacks
10. No cover on engine (the one that says D-4S Boxer).
11. No vanity mirror light, no puddle light.
12. No Cruise Control

This does not make sense to me.
WTF are the speakers for then?

[OkieSnuffBox]

Originally Posted by Yoniyama

Reducing front unsprung weight by 16lb is definitely worth the money and effort. I achieved similar weight saving by using a super-light wheel (Volks Racing TE-37 at 12.5lb each), 2-piece brake rotor (saving about 6lb each), light weight lug nuts, and hollow front sway bar.
The effect is noticeably positive on my 2018 BRZ. Of course the ride is much less jarring, and the steering feedback also improves. Now I can focus on the road ahead, rather than looking out for all the rough patch/pot hole to avoid.
I am now looking at replacing the front knuckle for another 3lb savings per corner.

His numbers should be per side, right? So it would actually be a 32lb savings on the front. A lightweight battery is another 15-20 out of the front.

So potentially as much 52lbs out of is pretty nice.

[Jianlun]

Originally Posted by x808drifter

This does not make sense to me.
WTF are the speakers for then?

Basically allows you to put whatever aftmkt HU.

[Jianlun]

Just to finish the conversation on aftmkt FLCA. Emailed most to check on fitment and these are some replies:

SPL FLCA
https://www.splparts.com/products/fr...-brz-ft86.html
They replied saying they redesigned/re-specced the ball join to cater for the Alu knuckle.

Cusco FLCA. https://www.rhdjapan.com/cusco-wide-...6-zn6-zn8.html Generic part for all gens and no report of compatibility (nor non-compatibility) with alu hub but marketed to be compatible.

P2M FLCA. https://www.phase2motortrend.com/pro...lca1086-hc.htm they replied saying they will check fitment with the alu knuckle, cannot confirm at this time.

Hardrace FLCA. https://www.hardracesuspension.com.a...er-control-arm looks like new part number specific for 2022 BRZ.

Megan racing FLCA https://
meganracing.com/suspension/type-suspension-arms/scion-subaru-arms/mrs-sc-0624-ii usd605
https://meganracing.com/suspension/t...-sc-0624-v2-ii
Looks like new part number specific for 2022 BRZ.

RacerX FLCA https://racerxfabrication.com/frs-br...r-control-arms
they replied saying they will check fitment with the alu knuckle, cannot confirm at this time

[euniqe]

That's great that the SPL FLCA's would fit the alu knuckles, but would the stock FLCA from the '22 fit an FR-S? Surely the SPL's would be lighter, but not sure about the ride comfort with rose-joints, would prefer bushes.

[Racecomp Engineering]

Also, in your front caliper weight for OEM, it does not look like you're including the weight of the caliper bracket.

https://www.ft86club.com/forums/showthread.php?t=7881

- Andrew

[Jianlun]

Originally Posted by Racecomp Engineering

It will be a good thing.

I can give you numbers on how it actually changes things later...I'm on vacation.

- Andrew

Would like to conclude this thread... May I refine my question one last time. Sorry...

Assuming there is a 20% reduction unsprung weight in the front but none in the rear, would the balance of the car change? Eg the front tyres are able to "follow" the road surface better and doesnt "fly off" the small bumps on the road, does this give more front grip leading to better turn in, higher braking/lock up headroom, maybe a more oversteery car on steady state sweepers cos the front end ultimate grip is more than the rear?

Also, I been reading on this topic a lot more the past few days and it does seem there is all good no bad and thus no such thing as too much unsprung weight reduction. And moreover the metrics to look at is actually the unsprung to sprung ratio. And the 20% reduction is absolute weight actually only means 2% reduction in the unsprung:sprung ratio which is insignificant.

Edit: just to complete the picture. Lightening potential for the rear limited to the RUCA. And i have the cusco one but more for camber fine tuning. No magical savings unlike the front.
Stock RUCA 8lb.
RacerX RUCA 4.1lb
Cusco RUCA 5lb

[x808drifter]

Originally Posted by Jianlun

Basically allows you to put whatever aftermarket HU.

So spend more money to remove the radio halfway to lose weight because racecar, and more if you wanna add it back in when aftermarket speakers can be lighter to begin with.