[kwan_1104]

^^ thanks man.....just placed my order
I LOVE YOU!!!!
went with 250f/225r though, cause they dont have 275f in stock

[StiLimited]

Originally Posted by stretch

275lb-in front, 225lb/in rear. You'll be a little underdamped, but not horribly so.

I'd highly recommend you get Ground Control's camber/caster plates to add bump travel to the stock struts. That's really the more important upgrade, much more important than the springs.

Probably a dumb question, but if someone were inclined to do so, could you use a strut brace on top of the caster/camber plates?

[4banger]

It depends on the plates. For the GC's, no.

[stretch]

I got the shock dynos from Mark (Ground Control). Kudos to him for taking the time to put these on the dyno, test them, and mail me the printouts.

Most interesting is that the front adjust does both rebound AND bump, something Koni's rarely do. There's a 1:1 to 1:25 bump-to-rebound damping ratio which is pretty good for performance. There's also a less sharp elbow in the graph compared with most Koni products, which I recall Mark saying was done for ride quality. Overall, the range of adjustability is ample up front but is much lower than what Koni off-the-shelf products usually have in the rear. GC does have many different Koni valvings available, though, so it's possible they ship different shocks based on your chosen spring rates.




I don't have time at the moment to really analyze these as much as I'd like, but hopefully 4banger will post up what spring rates these dampers are optimal for. I do know that on 350lb/in front springs, my car feels best at 1-1/8 to 1-1/4 turns past full soft up front. My WRX Koni inserts in the rear (dyno here) are 3/4 to 7/8 of a turn past full soft on 250lb/in springs. That doesn't mean anything really, but I thought I'd say what I've been running.

Higher resolution scans attached below:

[4banger]

Thanks for the plots, Stretch/Mark. I have to say, Mark is the man for two reasons. First is for providing these, no questions asked. Secondly, they use English units, which makes it a lot less work for me.

I'll try and have some numbers by the end of the day.

[4banger]

Here is my quickie 5 minute analysis (65% Critically damped):

Full Soft: 160/320 F/R (lbf/in)
Full Hard: 880/330 F/R (lbf/in)

I will do some more accurate analysis later. I should be able to get more accurate numbers for the STi Konis than the WRX Konis because these have data points right at 3 in/sec. That takes a lot of the measurement error out of the equation.

Also of note, the rears aren't as strangely valved as before. They don't get nearly as stiff as the WRX's did on full stiff. The fronts are also less stiff, even on full soft. That explains why Stretch needed to turn his Koni's up from full soft, whereas I recommended to BigSky that he run his fronts on full soft.

[4banger]

After taking careful measurments of the data I have come up with he following springrates for 65% critically damped on 3600lb car including driver:

STi Konis
Full Soft: 151/353 F/R (lbf/in) 1.2/2.3 Hz
Full Hard: 961/535 F/R (lbf/in) 3.1/2.8 Hz

For ease of comparison:

WRX Konis
Full Hard: 843/5994 F/R (lbf/in) 2.2/9.3 Hz
Full Soft: 365/154 F/R lbf/in) 1.9/1.5 Hz

A setup like Stretch's with STi Konis up front with WRX Konis in the rear may be the most desirable, because the lowest spring rate that the STi rears can damp properly is 2.3 Hz, which may be too high for someone interested in just a DD setup. However these would be great for someone looking for a 500/400 lbf/in setup.

[TraSTi]

Ok so i'm Planing on doing a setup for AutoX about 2 times a months on Rcomp (275's) and then some trackdays every once in a while (probably one every 3 or 4 months). This car is also my Daily driver. Other suspencion mods. 27mm sway set to 29 and 24mm sway set to 26 (or w/e the stiff setting is). This settings could change. I was thinking of 400/350 springs with STI Konis in the front and WRX in the rear. I would go SA. Would 8" swift springs do or is the 9" needed? I would also choose to go with GC plates for the extra travel.

I will be giving mark a call later on today and see what he thinks. Any Advice? BTW where can i find WRX take offs?

[4banger]

TraSTi. The spring rates look pretty good, but I'd be interested to know why you wouldn't choose 500/400. That seems to be the most popular choice for people that do track days. I guess you are more interested having a comfortable DD, so the 400/350 should be a good choice. Hopefully you won't need your sways to be that stiff now that your car will be properly damped.

Let us know what Mark says.

[TraSTi]

Talking to Stretch it seems that for AutoX (which I do way more than Track days) Softer springs with stiffer sways work well plus they are better for DD too. I already have the RCE Yellows Ver 1 which coilbind in pot holes so i'm kind of used to stiff... Maybe the 500/400 would do better for me. Is 400/350 stiff enough to run 275? I also though that the 400/350 setup might rotate better (for autoX) since the rear stiffness is closer to the front...


For some reason the RCE T2 just keeps calling me... In which case i still would have to choose between those spring rates

[stretch]

Well, the thing is that the sway bars don't seem to be doing as much as they should since the stock bushings (in all the suspension linkage, not just the sway bushings) are so soft. But yeah, in theory, changing springs has a fairly minor effect on body roll since 24mm sway bars should already be doing most of the work.

I just did fairly well at an autocross (fastest on street tires) with 350/250 rates, though I had a terrible amount of understeer. I wish I had firmer rear springs OR more camber up front and a smaller front sway. I can't really recommend rates with any certainty until I get my own car sorted out, but I'm sure I won't go much firmer myself.

That said, yes- if you're going to go with the Ground Control Koni rears, you'll probably want the 350lb/in rear springs (with 400lb/in front). 4Banger did the math (thanks) to show this. I think that sounds like a very good setup for an aggressive (but very streetable) car.

[4banger]

Stretch,
Hope you enjoyed your vacation. Where did you go?

After reading the entire TiC thread from start to finish a few days ago, I realized that all of my calculations have been neglecting the gas pressure in the dampers. It is easy to recompute the numbers but I have no idea what number to use. 75, 100, 150 psi? I'd also need to know the piston diameter, but that is proably somewhere in this thread. What do yout think we should use for the pressure?

[ButtDyno]

Originally Posted by stretch

I just did fairly well at an autocross (fastest on street tires) with 350/250 rates, though I had a terrible amount of understeer. I wish I had firmer rear springs OR more camber up front and a smaller front sway. I can't really recommend rates with any certainty until I get my own car sorted out, but I'm sure I won't go much firmer myself.

FWIW I would try the camber up front first You know you're gonna need that regardless.

I know that my car *can* be neutral with a 27mm front bar and a 17mm rear bar (with appropriate ride heights and alignments). At this exact moment (with higher ride height in the front than before) the car is not where I want it to be, but with the Cobb rear bar that should get here on Wednesday, I expect that I can run "normal" ride heights and still be neutral.

john

[AndrewSS]

Originally Posted by TraSTi

Talking to Stretch it seems that for AutoX (which I do way more than Track days) Softer springs with stiffer sways work well plus they are better for DD too. I already have the RCE Yellows Ver 1 which coilbind in pot holes so i'm kind of used to stiff... Maybe the 500/400 would do better for me. Is 400/350 stiff enough to run 275? I also though that the 400/350 setup might rotate better (for autoX) since the rear stiffness is closer to the front...


For some reason the RCE T2 just keeps calling me... In which case i still would have to choose between those spring rates

You are setting up a BSP car right? If you go with T2's and at least 275 v710's I would recommend at least the 500/400. I have found today that 600/500 springs with the WL 27 fsb set to stiff and now my stock rsb replacing my old WL 24 set to soft works quite well. Much less rear inside lift as it is now, with the old WL rsb I was lifting the rear inside all over the place. You probably will need at least 500lb spring in the back to prevent rub on the fender, that or you need to raise the car a bit more and or more neg camber (mines at 13 and like 6/8ths and -1.0). Also, I found that 500/400 might roll a bit much with v710's

Hope that helps, and is not too far off topic... heh

[AndrewSS]

Originally Posted by stretch

Well, the thing is that the sway bars don't seem to be doing as much as they should since the stock bushings (in all the suspension linkage, not just the sway bushings) are so soft. But yeah, in theory, changing springs has a fairly minor effect on body roll since 24mm sway bars should already be doing most of the work.

I just did fairly well at an autocross (fastest on street tires) with 350/250 rates, though I had a terrible amount of understeer. I wish I had firmer rear springs OR more camber up front and a smaller front sway. I can't really recommend rates with any certainty until I get my own car sorted out, but I'm sure I won't go much firmer myself.

That said, yes- if you're going to go with the Ground Control Koni rears, you'll probably want the 350lb/in rear springs (with 400lb/in front). 4Banger did the math (thanks) to show this. I think that sounds like a very good setup for an aggressive (but very streetable) car.

I agree with buttdyno... try camber! I have dialed out oversteer from my car recently, as it has been way too tail happy. What front camber do you run? I would say -3.0 ish minimum for the sti at an autox.