Hello. With some experience on the Super Pro 23F/22R setup w/ endlinks and bushing replacements but otherwise stock suspension save a performance alignment (so far) I wish to share my experiences on a fast autocross.
When braking hard and cornering steeply, my inside rear tire lifted. While the body roll is less on my STi than a lot of other cars as per the photos someone else took, and I had one of the better times of the day, faster than say Corvettes or E90 M3's! There was a tuner/mechanic present who has a lot of track/autocross experience that wanted to take a ride with me, and his eyes popped open at how hard I ran it for my best lap. This is important info because I really like how the 23/22 setup with otherwise stock everything else improved most of the GR handling gripes about excessive understeer when you would rather rotate the rear, snap oversteer when you don't want it, and excessive roll. In other words, if someone is going to DD alone their car, this setup feels pretty much ideal. At 7-9/10ths, combined with a performance alignment the car will really sing handling wise.
Once you start to push it though, I wanted to post that this swaybar combination either is not enough, or too much; let me describe. On the one hand, STi's can understeer because the tires will get positive camber when cornering, especially the fronts. Adding a front swaybar only, or a significantly stiffer front vs rear will help the roll and turn-in situation only so much, but by overloading the fronts, the understeer will also increase. Likewise, while a rear sway will also help, with or without a front, upping the rear swaybar will lead to tire lift. It's not the worst thing in the world, but long term is not ideal for differential life or accelerating out of the corner, as wheel lift tends to be worse at the apex when you really need to start applying power.
The solution to the GR's stock handling gripes then will depend on your intended usage of the car. While for DD, a performance alignment followed by swaybars and endlinks really is the be-all and end-all for a sweet handling ride, the most optimal setup probably being the front 1-2mm stiffer than the rear, robbing your suspension of independence will start to cause problems when driven at 10/10ths.
If a more motorsport purpose is needed, I believe that while neither sway should be terribly stiff, the front should be 2-3mm stiffer than the rear, and the extra added understeer scrubbing should come from a combination of
-camber plates with added caster and sensible amounts of negative front camber (start with 1.8 and work up from there)
-slightly stiffer springs once more than somewhat stiffer sways are needed with rear spring slightly stiffer than front as this combination works best for GR handling & ride quality.
-coilovers looking to increase compression resistance but lowering rebound, especially low speed,
-slight lowering, perhaps slightly more in the rear as a part of the corner balancing of your coilovers
in that order more or less.
It's easy enough, I will be lowering my rear bar to 21mm for autocross so I will be 23/21mm F/R and taking it from there. Other changes eventually pending, hopefully soon.
But the takehome point is that a performance alignment is magical with respect to handling, say stage 1 is to power in cost/benefit analogy mode. Stiffer swaybars are also quite good for the street with the added benefit of not compromising ride quality excessively, but as always, the fastest STi's for autocross and tracking actually had very stiff coilovers and soft swaybars. This is due to the car's front heavy nature and inside rear lift which is aggravated if you go for too much sway on the rear, yet also made to understeer if the front sway is pushed, taxing the front tires excessively as well.
What I wish to remind people which if you read this subforum, you probably already know, suspension mods should be done from a more "tuning" point of view. Just like you don't slap on a dom 3.5 and screw a methanol/water injection kit in your garage, then pull out of your driveway flooring it expecting the car to leave a 4 wheel burnout all the way to the end of your street, you shouldn't just bolt on suspension mods, feel the extra handling, and think it is good. You have to take the entire picture into account, and overly stiff sways, for which 23/22 would qualify, as good as it is for street DD as it is, will cause potential problems if employed in a harder driving environment.
DD doesn't need coilovers. Once you start to autocross and track hard, you don't need them, but you also need to consider alignment, ways to boost possible alignment settings, springs and coilovers as well, and this is what "suspension tuning" is all about.
Have fun!
T
When braking hard and cornering steeply, my inside rear tire lifted. While the body roll is less on my STi than a lot of other cars as per the photos someone else took, and I had one of the better times of the day, faster than say Corvettes or E90 M3's! There was a tuner/mechanic present who has a lot of track/autocross experience that wanted to take a ride with me, and his eyes popped open at how hard I ran it for my best lap. This is important info because I really like how the 23/22 setup with otherwise stock everything else improved most of the GR handling gripes about excessive understeer when you would rather rotate the rear, snap oversteer when you don't want it, and excessive roll. In other words, if someone is going to DD alone their car, this setup feels pretty much ideal. At 7-9/10ths, combined with a performance alignment the car will really sing handling wise.
Once you start to push it though, I wanted to post that this swaybar combination either is not enough, or too much; let me describe. On the one hand, STi's can understeer because the tires will get positive camber when cornering, especially the fronts. Adding a front swaybar only, or a significantly stiffer front vs rear will help the roll and turn-in situation only so much, but by overloading the fronts, the understeer will also increase. Likewise, while a rear sway will also help, with or without a front, upping the rear swaybar will lead to tire lift. It's not the worst thing in the world, but long term is not ideal for differential life or accelerating out of the corner, as wheel lift tends to be worse at the apex when you really need to start applying power.
The solution to the GR's stock handling gripes then will depend on your intended usage of the car. While for DD, a performance alignment followed by swaybars and endlinks really is the be-all and end-all for a sweet handling ride, the most optimal setup probably being the front 1-2mm stiffer than the rear, robbing your suspension of independence will start to cause problems when driven at 10/10ths.
If a more motorsport purpose is needed, I believe that while neither sway should be terribly stiff, the front should be 2-3mm stiffer than the rear, and the extra added understeer scrubbing should come from a combination of
-camber plates with added caster and sensible amounts of negative front camber (start with 1.8 and work up from there)
-slightly stiffer springs once more than somewhat stiffer sways are needed with rear spring slightly stiffer than front as this combination works best for GR handling & ride quality.
-coilovers looking to increase compression resistance but lowering rebound, especially low speed,
-slight lowering, perhaps slightly more in the rear as a part of the corner balancing of your coilovers
in that order more or less.
It's easy enough, I will be lowering my rear bar to 21mm for autocross so I will be 23/21mm F/R and taking it from there. Other changes eventually pending, hopefully soon.
But the takehome point is that a performance alignment is magical with respect to handling, say stage 1 is to power in cost/benefit analogy mode. Stiffer swaybars are also quite good for the street with the added benefit of not compromising ride quality excessively, but as always, the fastest STi's for autocross and tracking actually had very stiff coilovers and soft swaybars. This is due to the car's front heavy nature and inside rear lift which is aggravated if you go for too much sway on the rear, yet also made to understeer if the front sway is pushed, taxing the front tires excessively as well.
What I wish to remind people which if you read this subforum, you probably already know, suspension mods should be done from a more "tuning" point of view. Just like you don't slap on a dom 3.5 and screw a methanol/water injection kit in your garage, then pull out of your driveway flooring it expecting the car to leave a 4 wheel burnout all the way to the end of your street, you shouldn't just bolt on suspension mods, feel the extra handling, and think it is good. You have to take the entire picture into account, and overly stiff sways, for which 23/22 would qualify, as good as it is for street DD as it is, will cause potential problems if employed in a harder driving environment.
DD doesn't need coilovers. Once you start to autocross and track hard, you don't need them, but you also need to consider alignment, ways to boost possible alignment settings, springs and coilovers as well, and this is what "suspension tuning" is all about.
Have fun!
T
