From a physics and engineering stand point (BA in Electrical Engineering, AA in Auto Tech, ASE Cert) as Preface. No changes to wheel size and on the most popular Michelin Pilot Sport 4 A/S. From my understanding of theory, testing with different tire setups, and suspension tuning options on the GD chassis; To bring a stock STI to a Neutral turn-in would only require a 22mm rear on stiffest setting. If you decide to do Coilovers (as most do) then you'll need a bump-steering correction kit, front chassis bracing, a 22mm on stiffest setting or a 24mm on mid setting, Front Strut Tower Brace, a stiffer front spring rate (10kg max recommended for street, 14kg+ for track), a slightly stiffer rear spring rate (8kg max for street, 10kg+ for track), the adjust rebound and bump as needed for driving/track preferences. The reason for a soft-ish rear springrate is to allow the body to roll and allow the sway bar to perform it's torsional task of maintainin a specific amount of load. In laymen's terms, for the GD chassis, a Stiffer Rear sway will "add grip" because the added twisting resistance will keep the outside wheel on a turn, on the ground more often than not. (25mm+ is overkill unless you have serious downforce and power to be able to get it to lean at high speeds). Edit: after rereading, Solid End Links can provide a massive change in suspension feel and I would genuinely recommend it. But you will notice more bump-steer and some NVH within the chassis (Not too important on track cars n such)
bumped the playback speed to x1.5 and it gave the music a much cooler, peppier vibe. add more caster and make the rear a lower ride height than the front; along w/reducing rear toe.
sorry to just jump in and comments.. First thing first... u were attacking the wrong side of the car.. (well i gues not totally wrong side, but less important side) the most important side to solve understeery nature of a subaru GC/GD chassis lies up front suspension geometry.. 1- subaru GC/GD/SF/SG NEED MORE CASTER (stock factory caster value is around +3.5degree till about +4.0 degree) -there are several free/low cost yet reliable caster mod such as: a ) rotate your camber plate on the 3 axis strut top bolt so now the camber slot facing the windscreen of the car...these giving u 2 option. either 50-50 camber & caster at 45degree rotation, OR 100% caster increase and then camber adjustment relying on stock strut camber bolt at wheel hub (this where the most increase of caster came from) *Whiteline does have non adjustable OEM-like rubber strut mount called "Caster Com-C" mount (designed mainly for group N rally car use especially in tarmac rally application b ) front lower control arm there is big black steel pin holding the big lower arm bush.. u can rotate the pin installation face to gain about +0.5degree caster c) again front lower control arm big bush. comes with 2 option, 1st option is using forester SF5 bush that alter the angle of that lower control arm to be ANTI-LIFT / ANTI-DIVE geometry. 2nd option is buying the Whiteline bush. (comes in several more option either just anti-lift kit, or anti-lift with +0.5degree caster or anti-lift with +1.0degree of caster) d ) final caster mod from OEM is getting 07 hawkeye JDM/USDM "special Spec-C" front lower control arm with additional caster built into the design These mod above will nett around +6.0degree all the way up to +7.0degree of caster... but for road use i would recommend dial the caster to around +6.0degree or +6.5degree MAX... because over +7.0 degree of caster will increase steering "kickback" on bumps/dips of road surface while turning the steering... as benefits of caster, im sure u can look around trusted information reading online.. cheers 2- keep oem sti front swaybar (u were good on this already) 3- as for rear big swaybar...no comments..relies heavily on coilover damping rate, spring rate, tyre grip level and such... but im running whiteline 23mm rear with solid alloy C-link (22mm front on mine as comparison) 4- the rear swaybar link bracket on that Lateral Link installation is incorrect...the bracket should sit outside of the lateral arm facing rearward of the car. then u can use the solid C-link type swaybar link cheers. again im sharing what i have already tested.. and i swear by my forester sf5 with all listed mod above handles better than any stock sti or lightly modded suspension wise sti in my region.. (im on the another continent other side of the world) Finally, if u were planning to lower the impreza or any other subaru model, get the whiteline rollcenter adjuster kit up front... (or hardrace as alternative of similar part and function) *tie rod end and front balljoint with rollcenter geometry correction. cheers.. checkout my video showing the front caster plate mods that ive done on my forester sf5.. now it turns sharply and more positive steering feel under braking, early turn-in as well as mid corner and exit... wwwDOTyoutubeDOTcom/shorts/Sy6LPCkMwoU
Thanks for your content. I’m an Aussie on my 4th Rex, currently a blob eye that I’ve run 3-4 different suspension setups. I found the change/s that eliminated under steer on mine stock sway bars and pedders shocks was 1. Whiteline caster tops and 2. Returning to stock ride height. This increased front bite and body roll to the point where I’ll add a stiffer rear bar next to limit how much I can throw it. I find it’s possibly too responsive on the highway but great on dirt roads in the country where I am. If your running lower than sti spec I understand you would need a roll centre kit to compensate.
Thanks for sharing your experience and knowledge! This car will be lowered but maybe 2” or less. I have already installed a roll center kit from Tomioka which was the best solution I could find before having to break the bank on drop knuckles. I’ll definitely check out all the things you mentioned that helped. Thanks again!!
I’d watch Moto IQ’s video on how to set up a GD chassis , I’m running white line products and it made a world of difference keeping my car planted . There’s alot of great information in that video
IIRC the wrinkle failing has to do with the part not getting up to temp or staying at temp long enough (it didn’t cure completely). According to some forum posts it’s that or the powder is on too light. It looks like you have enough powder on there. Verify this but I think you can bake it again, make sure you get the manifold up to temp, then start your time. If you can get an ir temp gun use it on the thickest part of the manifold to make sure the metal is at temp. Good luck if you try again, I’m just passing through so I might not see your results.
Everything you said I did. Wasn’t even close to my first rodeo. Powdered coated lots of parts with different colors from prismatic. I always wait till the part gets up to temp before shooting it with my infrared temp gun. This powder specifies 375 for 15 min. I let it get a little higher than that actually, closer to 400 and left it in for an extra 5 min. I’m not sure I could have applied the powder thicker! This is why it’s a mystery to me that it didn’t wrinkle…
I'm not exactly sure why someone would believe that these changes would stop the understeer. The understeer is primarily because of the engine location in relation to the strut towers, the tires' grip ability, the driver's capabilities to drive at high speeds, etc. No sway bar is going to fix a broken driver. Anyway, tightening up the rear with a strut bar or similar would increase oversteer.
No one said it would stop understeer. Improve it, yes. Didn't you just prove that point by stating that stiffer rear = more oversteer? And I agree, engine location is a big factor which I specifically stated that fact in the video. Great point concerning driver experience and skill. Like most things nothing can replace experience. I would also add driver style is important and over looked. Because of this, there isn't one "right" way. Set up the car the way you think will work well. Get lots of seat time, and develop the car in the way that fits your driving style.
Exactly, thats why I am planning on stiffer rear sway which is what I was trying to explain. I probably didn't explain it very clearly in the video. Words are hard
the swaybar can not be adjusted in the air. the car needs toi be on the ground for the height of the car to be correct. 22mm front and back is more then enough. but get yourself front and rear tower braces you should also have a anti-lift kit.
Thanks I appreciate it! Can't they be fitted in the air just not tightened? I am planning on building some platforms out of 2x4 stacks for this and alignments. Already have Cusco tower braces for front and rear I'll be installing. I'll look into an anti-lift kit.
The groupn pink stuff is ok for what it is but whiteline is better, ive seen both in action, my friend has an sti s203 and i have jdm sti with whiteline goodies
Right on man! Yeah I don’t doubt the quality of Whiteline products. The car came with a whole kit which had 24mm bars for front and rear and I personally think it’s overkill. Don’t really need both something that stiff
Only thing being mixed is the sway bar. Wanted to see if it could work since I had it. The rest of the pieces are all part of the STI triple pillow ball lateral link set.
Improvments of sways = ALOT! Improvment of those arms = not much! I'd ditch the arms and switch for stock stick with the swaybars. Never heard anything about issues in the rear, I didn't even use polyurethane in the rear! You should read a bit more about swaybars. It's weird that you thought a stiffer would add grip. After the weight transfer is done and the opposite side where you are turning in is loaded, the stiffer axl would always have less grip.
My understanding is that it’s not the arms themselves that make a difference. It’s the fact that they are slightly longer so gives a wider stance, and pushes the end link forward as well as where they attach to the sway bar. Spec C rear suspension came as a kit with trailing arms, end links attached to the brackets, and the sway bar. They are designed to be used together. As far as stiffer equaling more grip, that’s not what I thought. Rather I’ve always been under the impression that because these cars have bad under steer, stiffer bar in the rear allows the back end to rotate easier when cornering which compensates for under steer. Not sure if that’s a correct assumption. Appreciate your insight! I don’t think I’ll ditch the spec c stuff just yet. I looked into switching them to the standard STI arms so id have more rear sway bar options. However the cheapest solution was to just get the pink bar and the spec c links. And you’re correct, I definitely have a lot to learn in terms of suspension tuning.
@@sleeper_motorsport I know! Aparently I commented on it! :D I still stand by the comment: "I've done alot of trackdays... and to me, the 2 top mods are: - front H brace - the steering is alot more direct. - Anti rollbars: either go Stock front | 22mm rear, or 22 front 24 rear. Next: 2.5" camber front 1.5" camber rear. And yes coilovers with a bit softer front than rear, as said on the video. Then... if you have an LSD you can reduce understeer with throttle."
Haha nice man!! Well thanks for the tips man! It’s great to be able to get help from people with real track experience, because I have zero. Only Karting which doesn’t help with suspension tuning on an actual car… I’ll definitely be considering all of the options you gave me! Thanks again
From a physics and engineering stand point (BA in Electrical Engineering, AA in Auto Tech, ASE Cert) as Preface.
No changes to wheel size and on the most popular Michelin Pilot Sport 4 A/S.
From my understanding of theory, testing with different tire setups, and suspension tuning options on the GD chassis;
To bring a stock STI to a Neutral turn-in would only require a 22mm rear on stiffest setting.
If you decide to do Coilovers (as most do) then you'll need a bump-steering correction kit, front chassis bracing, a 22mm on stiffest setting or a 24mm on mid setting, Front Strut Tower Brace, a stiffer front spring rate (10kg max recommended for street, 14kg+ for track), a slightly stiffer rear spring rate (8kg max for street, 10kg+ for track), the adjust rebound and bump as needed for driving/track preferences.
The reason for a soft-ish rear springrate is to allow the body to roll and allow the sway bar to perform it's torsional task of maintainin a specific amount of load.
In laymen's terms, for the GD chassis, a Stiffer Rear sway will "add grip" because the added twisting resistance will keep the outside wheel on a turn, on the ground more often than not. (25mm+ is overkill unless you have serious downforce and power to be able to get it to lean at high speeds).
Edit: after rereading, Solid End Links can provide a massive change in suspension feel and I would genuinely recommend it. But you will notice more bump-steer and some NVH within the chassis (Not too important on track cars n such)
bumped the playback speed to x1.5 and it gave the music a much cooler, peppier vibe. add more caster and make the rear a lower ride height than the front; along w/reducing rear toe.
The rubber cap on the lateral link bolt is for if you get into an accident, keeps the bolt from puncturing the gas tank.👍
Aw, got it that makes sense. Good to know! Thank you!
sorry to just jump in and comments..
First thing first... u were attacking the wrong side of the car.. (well i gues not totally wrong side, but less important side)
the most important side to solve understeery nature of a subaru GC/GD chassis lies up front suspension geometry..
1- subaru GC/GD/SF/SG NEED MORE CASTER (stock factory caster value is around +3.5degree till about +4.0 degree)
-there are several free/low cost yet reliable caster mod such as:
a ) rotate your camber plate on the 3 axis strut top bolt so now the camber slot facing the windscreen of the car...these giving u 2 option. either 50-50 camber & caster at 45degree rotation, OR 100% caster increase and then camber adjustment relying on stock strut camber bolt at wheel hub (this where the most increase of caster came from) *Whiteline does have non adjustable OEM-like rubber strut mount called "Caster Com-C" mount (designed mainly for group N rally car use especially in tarmac rally application
b ) front lower control arm there is big black steel pin holding the big lower arm bush.. u can rotate the pin installation face to gain about +0.5degree caster
c) again front lower control arm big bush. comes with 2 option, 1st option is using forester SF5 bush that alter the angle of that lower control arm to be ANTI-LIFT / ANTI-DIVE geometry. 2nd option is buying the Whiteline bush. (comes in several more option either just anti-lift kit, or anti-lift with +0.5degree caster or anti-lift with +1.0degree of caster)
d ) final caster mod from OEM is getting 07 hawkeye JDM/USDM "special Spec-C" front lower control arm with additional caster built into the design
These mod above will nett around +6.0degree all the way up to +7.0degree of caster... but for road use i would recommend dial the caster to around +6.0degree or +6.5degree MAX... because over +7.0 degree of caster will increase steering "kickback" on bumps/dips of road surface while turning the steering...
as benefits of caster, im sure u can look around trusted information reading online.. cheers
2- keep oem sti front swaybar (u were good on this already)
3- as for rear big swaybar...no comments..relies heavily on coilover damping rate, spring rate, tyre grip level and such... but im running whiteline 23mm rear with solid alloy C-link (22mm front on mine as comparison)
4- the rear swaybar link bracket on that Lateral Link installation is incorrect...the bracket should sit outside of the lateral arm facing rearward of the car. then u can use the solid C-link type swaybar link
cheers. again im sharing what i have already tested.. and i swear by my forester sf5 with all listed mod above handles better than any stock sti or lightly modded suspension wise sti in my region.. (im on the another continent other side of the world)
Finally, if u were planning to lower the impreza or any other subaru model, get the whiteline rollcenter adjuster kit up front... (or hardrace as alternative of similar part and function) *tie rod end and front balljoint with rollcenter geometry correction.
cheers.. checkout my video showing the front caster plate mods that ive done on my forester sf5.. now it turns sharply and more positive steering feel under braking, early turn-in as well as mid corner and exit...
wwwDOTyoutubeDOTcom/shorts/Sy6LPCkMwoU
Thanks for your content. I’m an Aussie on my 4th Rex, currently a blob eye that I’ve run 3-4 different suspension setups. I found the change/s that eliminated under steer on mine stock sway bars and pedders shocks was 1. Whiteline caster tops and 2. Returning to stock ride height. This increased front bite and body roll to the point where I’ll add a stiffer rear bar next to limit how much I can throw it. I find it’s possibly too responsive on the highway but great on dirt roads in the country where I am. If your running lower than sti spec I understand you would need a roll centre kit to compensate.
Thanks for sharing your experience and knowledge! This car will be lowered but maybe 2” or less. I have already installed a roll center kit from Tomioka which was the best solution I could find before having to break the bank on drop knuckles. I’ll definitely check out all the things you mentioned that helped. Thanks again!!
I’d watch Moto IQ’s video on how to set up a GD chassis , I’m running white line products and it made a world of difference keeping my car planted . There’s alot of great information in that video
Great suggestion! Thanks I'll check it out. Love Moto IQ
Thanks for this vid & comments of others! New to subi (track) life & particularly interesred in suspenion & brake system improvements!
Aussi also!
Thanks for the sub! Cheers!!
IIRC the wrinkle failing has to do with the part not getting up to temp or staying at temp long enough (it didn’t cure completely). According to some forum posts it’s that or the powder is on too light. It looks like you have enough powder on there. Verify this but I think you can bake it again, make sure you get the manifold up to temp, then start your time. If you can get an ir temp gun use it on the thickest part of the manifold to make sure the metal is at temp. Good luck if you try again, I’m just passing through so I might not see your results.
Everything you said I did. Wasn’t even close to my first rodeo. Powdered coated lots of parts with different colors from prismatic. I always wait till the part gets up to temp before shooting it with my infrared temp gun. This powder specifies 375 for 15 min. I let it get a little higher than that actually, closer to 400 and left it in for an extra 5 min. I’m not sure I could have applied the powder thicker! This is why it’s a mystery to me that it didn’t wrinkle…
I’m going to try throwing it back in the oven though like you mentioned and just see what happens.
Could be a bad lot of powder too. I’ve only seen wrinkle fail when it wasn’t cured. Hope you get it to work though.
I'm not exactly sure why someone would believe that these changes would stop the understeer. The understeer is primarily because of the engine location in relation to the strut towers, the tires' grip ability, the driver's capabilities to drive at high speeds, etc. No sway bar is going to fix a broken driver. Anyway, tightening up the rear with a strut bar or similar would increase oversteer.
No one said it would stop understeer. Improve it, yes. Didn't you just prove that point by stating that stiffer rear = more oversteer? And I agree, engine location is a big factor which I specifically stated that fact in the video. Great point concerning driver experience and skill. Like most things nothing can replace experience. I would also add driver style is important and over looked. Because of this, there isn't one "right" way. Set up the car the way you think will work well. Get lots of seat time, and develop the car in the way that fits your driving style.
Buddy, always read your whole comment before posting it. Lmao
@@CondorrK haha. Boooo
@@sleeper_motorsport i said the rear because stiffening the rear increases oversteer, thus reduces understeer. Stiffening the front does the opposite
Exactly, thats why I am planning on stiffer rear sway which is what I was trying to explain. I probably didn't explain it very clearly in the video. Words are hard
the swaybar can not be adjusted in the air. the car needs toi be on the ground for the height of the car to be correct. 22mm front and back is more then enough. but get yourself front and rear tower braces
you should also have a anti-lift kit.
Thanks I appreciate it! Can't they be fitted in the air just not tightened? I am planning on building some platforms out of 2x4 stacks for this and alignments. Already have Cusco tower braces for front and rear I'll be installing. I'll look into an anti-lift kit.
@@sleeper_motorsport nohing fits like it should. so loosen it up and fix it when you get it on the flor or something that kompress it equal
The groupn pink stuff is ok for what it is but whiteline is better, ive seen both in action, my friend has an sti s203 and i have jdm sti with whiteline goodies
Right on man! Yeah I don’t doubt the quality of Whiteline products. The car came with a whole kit which had 24mm bars for front and rear and I personally think it’s overkill. Don’t really need both something that stiff
Aren't you just attempting to mix narrow and wide track parts together
Only thing being mixed is the sway bar. Wanted to see if it could work since I had it. The rest of the pieces are all part of the STI triple pillow ball lateral link set.
Improvments of sways = ALOT!
Improvment of those arms = not much!
I'd ditch the arms and switch for stock stick with the swaybars. Never heard anything about issues in the rear, I didn't even use polyurethane in the rear!
You should read a bit more about swaybars. It's weird that you thought a stiffer would add grip. After the weight transfer is done and the opposite side where you are turning in is loaded, the stiffer axl would always have less grip.
My understanding is that it’s not the arms themselves that make a difference. It’s the fact that they are slightly longer so gives a wider stance, and pushes the end link forward as well as where they attach to the sway bar. Spec C rear suspension came as a kit with trailing arms, end links attached to the brackets, and the sway bar. They are designed to be used together.
As far as stiffer equaling more grip, that’s not what I thought. Rather I’ve always been under the impression that because these cars have bad under steer, stiffer bar in the rear allows the back end to rotate easier when cornering which compensates for under steer. Not sure if that’s a correct assumption.
Appreciate your insight! I don’t think I’ll ditch the spec c stuff just yet. I looked into switching them to the standard STI arms so id have more rear sway bar options. However the cheapest solution was to just get the pink bar and the spec c links. And you’re correct, I definitely have a lot to learn in terms of suspension tuning.
The person in this video has a great explanation of this topic.
th-cam.com/video/UNhrkHyE1hs/w-d-xo.htmlsi=rYPxnr1pxti5ccJD
@@sleeper_motorsport I know! Aparently I commented on it! :D
I still stand by the comment:
"I've done alot of trackdays... and to me, the 2 top mods are:
- front H brace - the steering is alot more direct.
- Anti rollbars: either go Stock front | 22mm rear, or 22 front 24 rear.
Next:
2.5" camber front
1.5" camber rear.
And yes coilovers with a bit softer front than rear, as said on the video.
Then... if you have an LSD you can reduce understeer with throttle."
Haha nice man!! Well thanks for the tips man! It’s great to be able to get help from people with real track experience, because I have zero. Only Karting which doesn’t help with suspension tuning on an actual car…
I’ll definitely be considering all of the options you gave me!
Thanks again
How for the set shipped to 94591?
Send me an email and I'll send you an offer. sleeper.vibe@gmail.com
hi m8 i'm rebuilding my gc8 and i'd like to buy those swaybars but i'm from italy could you ship the to me?cheers,great content btw very usefull
Hey, thanks for the interest but these already sold yesterday morning. Cheers!