Singh_snisen

That's tru. Stiffer is not always better. U want ur dampers to do the most work. Not the spring.

s2000Junky

You set the spring rate/sways included) based on the lateral grip your tire generates ie width and compound and how you want that traction displaced front to rear, it should be a matched and balanced system working together to maximize traction and body control. The weight of the car as well as driver preference will have some bearing. Too stiff, your losing traction, too soft you lose body control. Grip forces from the tire put G load on the suspension. Bump response is mainly handled through the damper valving/settings.

DavidNJ

Your profile says you are running in NASA TTB. Could you share some setup info: shocks, ride height, and any aero pieces. What criteria will you use to determine if the rates are too stiff or too soft? 3Hz should be within the range of a track-only car without aero and mid-range of a car with significant aero. I believe 3Hz is about 1200 lbf/in in the front.

The car in your profile picture appears to have been lowered and has aero including a large front splitter that appears to be less than 2" off the track and a large rear wing. What spring rates do you use to keep the splitter off the ground under braking and the car off the bump stops at high speeds?

Tougefactory

I

In My Signature I am on Stance XR1's with 16k Springs all around.
This Season I am switching to Stance XR3 (3 Way Coilovers) and 16K front and 14K Rear

DavidNJ

I don't see it in your signature...just the picture and three links.

The spoiler is your own creation? How high is it off the ground? Does it scrape? Did you have data acquisition on suspension movement?

Tougefactory

I'm sorry for the confusion. I was stating that at the time of the photo in my signature i was on Stance XR1.

My splitter was something that I worked with Touge Factory (before I worked here to create.) i tried to go over it a little in this article. Bad To Rad Part 3: Devin’s S2000 Gets Cooler | Speed Academy
i did brake mounts at Road Atl that made it scrape a lot. So much that I think I have to retire it. I don't have data of the suspension movement at this time but that is something that we are going to do with suspension pots
from my teamates at Professional Awesome. The splitter was about 2 inches off the ground. it did scrape under braking.

DavidNJ

Without suspension movement data, how do you determine how much downforce you are generating? Did the top fender louvers pictured in the article get added to the car? How did you determine the effectiveness of the different diffusers? Did you ever have porpoising when the front splitter sealed against the ground?

The shocks play a big role in how stiff the tires perceive the suspension to be. The force of the spring is a function of displacement, in the shock a function of velocity; track surface imperfections on asphalt/concrete race tracks tend to have low displacement. Many appear to drive 16 kgf/mm (~900 lbf/in) springs on the street in dual purpose applications. That implies there is at least a possibility that the optimum point may be higher.

Aero present on many cars changes that, often requiring a trade-off between mechanical grip and downforce. It seemed curious that no one was saying they had used stiffer springs reporting a better or worse result. Some have said at lower rates they did feel the car pitched/heaved too much under braking. On some sports racers and formula cars, a heave spring is added to the front. Piper even added this to their Formula Fords which these days have minimal downforce, their bodies designed for low drag. In high aero configurations even higher spring rates are sometimes used. In oval racing the front aero is important enough that the cars use very soft primary springs with very stiff bump springs holding the front airdam around 1in +/- .25in off the road surface. (325-350 lbf/in used to in front, now 100 lbf/in springs with 1200 lbf/in bump springs and tiedown shock settings).

Tougefactory

You can determine downforce through other means of measurements as well. We used computer simulations to determine the ball park range on what downforce we should be making. With out suspension pots how ever or a wind tunnel we can't get these numbers in real time. we never installed those vents in the fenders because we are waiting on Trackspec Motorsports to send us some more refined louvers and bigger. We also have a new splitter/hood ducting that should create two time the amount of downforce in the front of the car. Determining different diffusers are all done in CAD. You want the splitter as low as possible but you do not want it touching the ground at all. it loses all its effectiveness when that happens.

No.Division

Car was TTB but now that those rules are gone its being built for ST4. Shocks are Ohlins TTX36's, Ride heights will be somewhere around 13/12.5" in the front with 1/4" of rake, Voltex Type 7 Wing and 4" spiltter are being added. I have a suspension model spreadsheet with a bit of tire data in it to estimate Lat G and balance. I did a few iterations till I found the Lat G's wasn't going up and the balance was neutral before considering the extra grip and balance change from aero at higher speeds. I have ride height sensors and am planning to build a data setup over time. Till then its just a bit of trial and error and some testing. If I need to go stiffer I will wait till I need the shocks rebuilt and revalve them at that time.

DavidNJ

The swan neck Voltex Type 7. And a great selection on the shocks...other than many be some of the special F1 shocks and Ohlins TTRs, probably the most advanced shocks on the market. Are you ordering them with digressive valving and/or a blow-off piston? Their only drawback seems to be needing a shock vacuum to bleed them. Are you also planning on testing different camber angles? Lot's of people on the forum seemed to stop at around -3.5°. Hoosier is recommending -4.0° for Spec Racer Ford fronts. Roger Caddell at AIM Sports has said that they found the limit on negative caster being an improvement was when the car was hard to stop on a Mustang in a semi-pro series.

On topic, the downforce from a good splitter and wing plus the questionable geometry in lowered S2ks are reasons I was curious if people were running stiffer springs.