[qwksti]

NICE job,, ill try to come next time,, maybe when you do TA we can rent a trailer and ill tow you there...

[Turninconcepts.com]

I think an interesting point to all this is the 08 sti. It is by no means tail happy. In fact, quite the opposite. It sticks like glue in the rear, but at the same time so does the front. Some perceive this as being slower due to the apparent lack of rotation, but in all of my testing and driving in it the car is much faster on a nearly stock suspension than pre 08's. Much of this is likely due to the track width increase and redesign of the rear usspension, but what I want to highlight is that I would much rather increase front grip over decreasing rear to correct the problem as that is going to be faster in the end.

That is all. I know you guys know what you're talking about and I know ESmooth chose what he did for good reason; he's knows his stuff!!

Tony

[XDNBC]

Originally Posted by ESmooth

Concerning the stiffness, with the hoosiers, I feel that I need the relatively high spring rates due to the grip they offer along with the good sized bars. Ive run on track with 400/350 springs and 500/400 with some different sway bar setups including the WL 27/24 and it just seemed to roll too much without the higher rates.

I am thinking of getting the T2s but am not sure whether to get 500/400 or 400/350 springs. I race in STU and do HPDE track days but haven't considered Time Trials yet. What were the differences you felt on those 2 spring combos with 245/40 street tires?
BTW: I currently have camber plates and WL 27/24 swaybars, and run -2.5F and -1.8R camber.

[ESmooth]

Id say to stick with the stiffer rates. Even with the 27/24 bar setup I had a fair amount of inside tire lift with the 400/350 springs. Daily ride quality was better but I felt it really suffered on track. In the following pics I had the hotchkis front bar(hollow 25mm), WL 24 rear on stiff with the 400/350 with the recommended track comp/reb settings and you can see there just wasnt enough roll resistance...granted I was using hoosiers which have much more grip than street tires. Even so, any car thats getting track use is probably going to be better off with the stiffer rates.





Even after going to the 27mm front bar I had a fair amount of inside tire lift with the softer spring rates, just dont have any good pics of that at the moment. With the 500/400, rear tire lift was all but eliminated.

By comparison, heres another shot of the same corner albeit the other direction with the 500/400 rates, no lift to be found:

[MGizzle]

Ok, I see why you did what you did but I still think there is plenty to do without spending time on swapping parts.

First off, how did you get to your camber set up and did you play with pressures?? When I want my ride to rotate I usually just play with pressures instead of going to extremes like ARB's or different springs.

Your car "rotating" and getting the end around is NOT what you want. It is slower than neutral. Hence, rotating just a bit is good but how much rotation is bad?? Hence why I don't understand why so many people are about making their car rear get loose.

As far as your front end having too much grip that is counter intuitive since you are stating you want more rear end rotation, which measn your car is understeering and the rear has more grip. This is why I was stating that going softer in the front will give you more grip and overall reduce your understeer and maybe even give you some rotation.

Finally, your rear picking up is GOOD for rotationg, bad for grip. As soon as that sucker lifts your roll resistance sky rockets and you loose rear grip tremendously. From my experience the wheel lifts because the rear is too stiff. Think about it. Your outside ARB moment arm goes up, pushing the inside up with it. Yeah, the inside is pushing down BUT WITH ITS WEIGHT ONLY, which is nothing compared to the weight on the outside. With stiffer ARB bars this is more evident in my experience because the bar is simply stiffer and picks the inside up more. Also, your weight transfers is faster to the outside (and stiffer springs will do the same) because the overall stiffness is higher.

Also, remeber that you have coilovers and that you can "effect" the TRANSIENT response by playing with the dampers, hence you can effect rotation with just damper settings. I am not sure how much play you got with the T2's but I guess something to look into.

Finally, I have found myself using the AUTO diff setting more and more on my currently stock suspension when I am at the track because I can't stop my ride from loosing the rear with the setting in the back. It is not too excesive but my laptimes are lower. Having said this, I would drive that car AS IS set up wise 2-3 track days and try out different driving things to see if you can effect it by just adjusting yourself. I sucked when I just got my STi because I was plowing through every corner. I haven't changed squat and now I am looking for less oversteer. It is crazy how subliminally you change your driving over time. The same happened to me last weekend on a go kart. I was plowing like crazy on right turns, ran 33sec lap times, and then just changed my driving after 10 laps and was hitting 31's.

Anyhow, I am real curious about your changes and what happens to the car. Keep us posted of any changes man. Later.

EDIT: Oh, I forgot to ask, with this roll center fix is your roll center higher, lower and where is it with respect to just dropping the car (ball park)?? I forgot from all the previous posts what it does to the RC's. I am thinking that slamming your car can't hurt since the CG height has a bigger effect on roll than where your roll center is (as long as that RC is not switching between over and under ground plane). Your car doesn't look really slammed in the photos so lower CG could help. Look at that one picture where you are turning left and it looks like most of the weight is on that front right tire. Your rear doesn't look compressed at all and fixing that could improve grip a lot.

[stretch]

MGizzle: The roll center kit compensates for roughly 10mm of lowering. The roll center starts dropping at ~2.6 inches for the first inch of lowering and accelerates to a 3:1 ratio, so roll couple does accelerate fairly quickly with lowering.

Esmooth, I'm not surprised you had lift while running the 24mm bar in combination with the 1" hollow bar up front. However, I'm surprised that the 27mm front bar did not fix this whereas the springs did. That sway bar has a drastically higher effect on your roll resistance than the springs. Furthermore, the relative spring stiffness didn't change much, and just going stiffer won't affect weight transfer at all (just how perceivable it is). It's possible that your rear wheel still gets completely weightless due to weight transfer, but it's harder to see and feel now.

[ESmooth]

MG, Ive done about 5 track days on the T2s with my 500/400s 27/24s and the understeer has been a consistent issue with pressure changes and aggressive rotation tactics. Its not so much about rotation as it is reaching neutrality which I was not getting. Adding front grip was what I was going for although it seemed no matter what I did, I couldnt get it to change, that includes changing bar settings, maxing out my camber plates and bolts along with maxing out my dampers and even going with rear toe out to reduce stability. At the end of the day its all about balance and the balance I have now with the stiffer rear springs is better than it was with the softer ones. The hoosiers I use, while very grippy, tend to bring out the understeer more than in street tires which I experienced mostly at buttonwillow going back to back. The limit of the hoosiers are much higher than street tires and getting them to come around has been a bit of a challenge. At the end of the day, I dont at all feel like I have a lack of front grip since turn in is strong, its just that mid corner push where the rear doesnt seem like it wants to come around. Midway through my second session on the hoosiers, I could still feel the sensation of understeer so it just seems that with those tires, the rear needs to be freed up a little bit more than it would with street tires. Next time I plan to stiffen up the front bar and maybe drop the rear pressures a bit to dial it out since its gotten to be pretty minor at this point.

Stretch, you know more about the concenptual part of the suspension and setup so Im sure your understanding is better than mine. That being said, this change certianly worked on my car and Im much happier with it. Im sure that adding more rear bar along with some other changes would give similar results, but this particular change really did the trick. As for the tire lift, most of it was happening at turn in and not causing any diff knocking or problems but it defnitely seemed to be caused by too soft of a front end. Part of me likes having all 4 tires on the ground at all times even if some daylight under the inside rear makes for more exciting photos :P

[qwksti]

have you tried setting the dccd to full rear? i prefer this setting and the car seems to rotate more than in auto mode.

[ESmooth]

Actually I havent played with it much recently. Pretty much everyone I know and talk to finds their times are slower with anything but auto, even if they like the feel of it better.

[MGizzle]

You could try to lower the rebound setting on the rear dampers to see if that helps with the rear wheel. That one picture where it shows the wheel lifting is surprising to me. You are not really rolling that much yet your rear is up. However, it doesn't seem to be in droop too much hence maybe the damper rebound setting is too agressive.

[qwksti]

Originally Posted by ESmooth

Actually I havent played with it much recently. Pretty much everyone I know and talk to finds their times are slower with anything but auto, even if they like the feel of it better.

ya i heard that as well. but at the last autox i went to i did half my runs in auto and the other half in full rear. all my times were better with the dccd in full rear. not sure if that was because i was learning the track better or not. but.. even in the manual it says "to go faster around the turns use full rear setting". "To go faster in a straight line use auto". probly minor in times,, but to get the car to rotate it may improve that for you.

patrick

[stretch]

Originally Posted by MGizzle

You could try to lower the rebound setting on the rear dampers to see if that helps with the rear wheel. That one picture where it shows the wheel lifting is surprising to me. You are not really rolling that much yet your rear is up. However, it doesn't seem to be in droop too much hence maybe the damper rebound setting is too agressive.

...which would explain why the firmer springs did the trick when they're otherwise a small part of the overall roll resistance and shouldn't have had much impact on handling bias. Nice catch.

[Lutfy]

Originally Posted by ESmooth

time I plan to stiffen up the front bar and maybe drop the rear pressures a bit to dial it out since its gotten to be pretty minor at this point.

Hello Eric,

Any update on running the bar on full stiff? I have had similar experience running a very similar setup (as yours). Just curious if you found the stiffer setting on the front bar to get you more mid corner grip.

Regards,

Lutfy

[XDNBC]

ES- I am not sure what cornering style you use, but I am running 27FSB, 24RSB for Solo2 and track [stock suspension with PDE campber plates [-2.7F, -1.6R] and can get oversteer by trail braking into a corner and getting the rear to step out while doing this. If I then get on the gas at apex, the back end stays out and I get slight power oversteer even at 3/4 and then flat out WOT. I think I want coilovers because I feel the springs bottom and get twitchy transitions there and I want to lower the car and fiddle with damping. Besides, all the other ST cars have them and an extra .5 seconds means a lot here [except for the STS Hondas- which are 2 seconds faster and have a .816 PAX :>( ].

BTW: I just finished a 2 day Solo2 event and was PAXed at 44 out of 96 on a sunny Saturday and finished 29/96 in the combined standings for the weekend because it rained on Sunday. My 2007 STI was only 1 second slower than a DM go cart on Hoosier rain tires, and I beat all but 1 BS car [why they have the same PAX as STU is beyond me]and most of the AS cars. Subaru drivers should definitely learn how to pray succesfully for rain to the AutoX gods

[ESmooth]

Actually, I have not done any events since the last track day when I posted this. I take the summer off since its usually 100+ degrees from June through August at all the local tracks. I probably wont be back out until ButtonWillow in mid-September after it cools off a little, but Ill certainly report back on the front bar at full stiff.