Spring rate combo's.. what's worked / what hasn't?

rlhammon · 10-29-2009, 02:55 PM

OK.. I know everyone has different setups and preferences, but basically all of our cars weight the same, carry the same corner weighting, etc.

So, I'm wondering what spring rate combination people have tried, and what worked / didn't work.

I know people have opening spoken about rates from 400 - 550 lbf/in in various posts, but what did people run front / rear and what worked / didn't?

Anyone willing to share (publicly)... Some have PM'ed me and e-mailed me, but I'm not willing to divulge someone else's information... not my place to do so, but I'm hoping we can start putting together a library of information here for others to use.

Daywalker · 10-29-2009, 03:05 PM

Keep in mind that driving style will to some degree dictate what rates work for some and not others. Also if the car is track only, street only or street/track. That info might help as well.

wspohn · 10-29-2009, 04:53 PM

I ended up with 450 lb. front and rear (ordered softer on the front but they shipped the same F&R so I fitted them to try them out.) Turned out to be quite good that way.

Stiffer would be uncomfortable for the street, softer would be less crisp handling.

Don't forget that it isn't just springs - you need to have a package with stiffer shocks as well.

rlhammon · 10-29-2009, 08:59 PM

@Daywalker & @wspohn:

Both are correct.. but seeing as this is the Autocross forum, I was thinking mainly in respect to that type of driving style.

I received in my Z0K rear bar tonight, and have done some more calculations. I'm thinking 450# front and 500# rear would be looking good. With some adjustable shocks I might be able to soften it up a bit for daily driving, but still be good for autocross. Might not be perfect for autocross, but she's not a trailer queen.. so I might need to do some compromising with springs.

DrJones · 10-30-2009, 11:28 AM

Snaponbob, what are you running :P

I figured I'd ask you since you always ask me. I guess I'll tell you if you tell me? I'm planning on changing/playing with them at the first test-n-tune next season anyways, but nothing crazy diffrent from what I have now.

rlhammon · 10-30-2009, 12:50 PM

Quote:

Originally Posted by DrJones

Snaponbob, what are you running :P

I figured I'd ask you since you always ask me. I guess I'll tell you if you tell me? I'm planning on changing/playing with them at the first test-n-tune next season anyways, but nothing crazy diffrent from what I have now.

I'd tell ya his... but I don't want to "out" anyone's information. I think each of us have talked to each other either in person, PM, or e-mails... and we all pretty much know where one or two of the others are at.

For me.. even if my car was identical in setup... I don't think I can currently outdrive Alex. I don't know against anyone else, but at least I've had some experience against Alex, and have seen him drive so I'm making that assessment.

I'd rather just share information and make the crop of Kappa's that much better. I'm not worried about being beat at any event, so what... I just want to be the best I can and if that means I'll finish no better than 10, so be it.. if it means I can win it all, great.

I can collect everyone's information and post it here if ya'll want.. I won't link names to anything.

snaponbob · 10-30-2009, 07:55 PM

Okay Alex. Actually, I have already posted elsewhere what I have under my car. I'll go one better!!! I'll tell where I am GOING if you do the same !!!!

After NO math (now I have a spread sheet program that I am crunching numbers with), I simply grabbed some springs from a guy with some 7" stuff. Since I had just installed threaded sleeves on my Konis, I needed to start somewhere. The car would spin out pulling into a parking place !!!!!!!!!! FAIL. But, I started to understand some things about this platform. IT RESPONDS to changes, and once you get near it's "sweet spot" it starts responding with smaller changes. Figuring that with 175f/220r springs it was an understeering setup (typical GM) I went way up on rate and opened the spread quite a bit. See above! As I glommed on to used pairs of 8"x2.5" springs I was coming down in the rear and up in the front. With the car lowered and stiffened the dynamics changed with stiffer springs probably because the car was rolling SO much less and the tires were not changing camber so much. Immediate benefit was lower pressures and better temp readings with greater response and grip. I finally settled in at 400f/450r and went after bars. I had already installed poly bushings in the control arms (oh, THAT was fun). I ordered both GXP/Z0K bars. Earlier I had done an SCCA legal install of the probeam. In all of this I was actually doing FEWER events this year and with concrete being a new factor I had to first learn on asphalt (as events came up) and then make changes for asphalt. The FE3 front bar and Z0K rear bar was too loose on asphalt which meant that it would be about right on concrete, and I was right. With 2009 meant only as a setup year, I still played with 450s all the way around and both Z0K bars. It seemed to be okay at Lincoln, I played with rear ride height to change roll center, and was fairly happy with it. I should have gone back to the FE3 front bar and 400s on the front, but I had run real well at Lincoln a few weeks earlier on the heavier set up on the front and left it in place. I f'ed up, and should have softened the front a bit. With SA Konis a bit above mid way on rebound (+/- personal preference) the car is really quite manageable and livable on the street.

I have been crunching numbers, looking at motion frequencies, theories, etc., and what I have already learned. After seeing the "how to REALLY drive an SP Kappa" clinic Alex put on at Lincoln, I had a shopping list in my head before I got to the interstate after Nationals. As more than one build has shown me, as the spring rates go up one needs to NOT look at the RATE as much as the PERCENTAGE wheel rate increase you want and THEN select the springs. Aiming at about a 2.3-2.4hz rate at the rear I will be starting at 600lb rears and try first 500 and then 550 front springs. If I was trailering the car, I would go higher, but I drive it. These same builders told me to rough tune the handling with the springs, and then tune further with the bars, and they were RIGHT. The FE3 front bar will stay on the front going into 2010.

Looking at pictures of Alex's car and mine at the same places at Lincoln I will be dropping the car a bit more and adding back the camber I thought should be removed (and I was WRONG !). My pockets only allowed 18x9 OZs for 2009 but even before I saw Alex's car I knew I would have 18x11's for 2010. Driving style dictates the final small tuning such as shocks, alignment, pressures, etc. Alex is MUCH more "point and shoot" then I am, and most of the quickest pilots in the faster classes do the same. THAT is an adjustment that requires NO tools, just some well executed mental commands. Oh, did I mention I was going to get 80-100 pounds off the car? Hey Alex, that A/C compressor weighs under 10 pounds - mine is staying on !!!!! Prediction - I'll scape 2940 and Alex will scale 2890 !!!!!!! A fiver says I am close. See ya at the scales at Lincoln Alex.

And he will still beat me. He's good.

Damn it !!!!!!!!

Somebody call the wambulance for me.

Okay Alex, you're up. Everybody take notes. He trophied and I didn't.

davytudope · 10-30-2009, 08:06 PM

i have the kw v3's. stock they where 285lb front and 228 lb rear. i ordered custom springs from them. 340 lb front and rear. they still are comfortable for a dd, and drive better on the ax. but nothing that would be competitive on a national level. but neither are my tires or myself.

snaponbob · 10-30-2009, 08:20 PM

In Solo, those heavier front spring set up with ANY combo of bars would be a snow plow. Street, okay. Auto-x, yuk. The folks at KW in Germany must have been selecting spring rates based on NO bars. Seriously.

davytudope · 10-30-2009, 08:26 PM

Quote:

Originally Posted by snaponbob

In Solo, those heavier front spring set up with ANY combo of bars would be a snow plow. Street, okay. Auto-x, yuk. The folks at KW in Germany must have been selecting spring rates based on NO bars. Seriously.

yes it was a plow, and i think kw just guessed with the spring rate.

snaponbob · 11-01-2009, 10:06 AM

Quote:

Originally Posted by davytudope

yes it was a plow, and i think kw just guessed with the spring rate.

Davy, try going up 1K on the back springs. Go very easy on the compression setting on those shocks. Basically, the compression has been increased with the springs, so you may want to take out a click or two. Conversely, you would well served by INCREASING the rebound from where it was with the original springs as that is needed to control the increased spring rates.

I really can not imagine why/how they chose the rates that they did. If they drove a Kappa with their setup they certainly would have felt the errors. How they may have modeled this is a matter of conjecture. Maybe somebody with suspension modeling software and experience can add something. I just have somebodies spreadsheet to calculate some stuff.

Alex? Are you there ?!?!?!?!?!

DrJones · 11-02-2009, 07:07 AM

Yes I am. I don't get around a computer too much on the weekends.

This whole season I was running 550 lbs in the front and 450 in the rear. The season before I had them the other way around but this felt a little better. I chose these targets based on the body natural frequencies.
Next year I plan on slightly adjusting the front springs. I'll probably try a set of 500 and 450 spring on the front. It felt like it would push a little too much this year. I'll also play with raising the ride height.
My Koni DA's are set pretty low on compression and maybe halfway stiff on rebound. I'm not sure the Koni's have enough range to really really make a change. Just get them in the ball park and it should be good.
I'll also be playing with rear bars this year. Not sure if i'll pick up a Z0K rear bar and modify it or just modify the FE3 rear bar.
Also:
Removing the Radio, Speakers and A/C.
using Kirkey race seats.
making sure washer fluid is empty.
looking to nitpick any (free) weight within the rules.

remember, that ounces add up to pounds.

rlhammon · 11-02-2009, 11:50 AM

I want to thank everyone for sharing.. I truly think this makes us all better, and puts information out there for everyone to use. Plus... it prevents the budget constricted (like me) folks from having to purchase the wrong things multiple times first!

I still have yet to get my car on the scales... in fact I'm having no luck finding anywhere around me where I can get the car up on four scales for some measurements. I realize everyone's setup's are different.. but does anyone have "stock" weights (and unsprung mass)?

I realize each car in "stock" condition is different based on options.. but I'm having a hard time understanding the magnitude of spring rate changes people are trying since I'm still missing another set of variables. If I can get my car up on scales sometime soon that would be great.

snaponbob · 11-02-2009, 12:24 PM

Quote:

Originally Posted by rlhammon

I want to thank everyone for sharing.. I truly think this makes us all better, and puts information out there for everyone to use. Plus... it prevents the budget constricted (like me) folks from having to purchase the wrong things multiple times first!

I still have yet to get my car on the scales... in fact I'm having no luck finding anywhere around me where I can get the car up on four scales for some measurements. I realize everyone's setup's are different.. but does anyone have "stock" weights (and unsprung mass)?

I realize each car in "stock" condition is different based on options.. but I'm having a hard time understanding the magnitude of spring rate changes people are trying since I'm still missing another set of variables. If I can get my car up on scales sometime soon that would be great.

I have scaled my Redline a few times. With OEM wheels/tires, the car scales at 3050-3100 (depending on fuel load). The fore/aft is 51.8/48.2%. Without driver the left/right is almost perfect. Without moving weight in the vehicle it will be very hard to compensate for driver weight. In using the calculation spreadsheet I was sent, unsprung weight does not have any meaningful effect on wheel rate and motion frequency calculations. As a 'swag' (simply wild ass guess) I factored 100lbs front and 110lbs rear (half shafts) as I felt no need to disassemble the suspension to get the "nth" degree. The greatest benefit in reducing unsprung weight is for a bit better acceleration, braking, and initial turn in (racing).