Spring rate help?

GSS138

I am actually going to talk to these guys the next time I run with POC. Their bars are the shizzle, custom made, easy to adjust, and they even make internally adjustable options. I doubt they will so don't get you hopes up. But I am going to ask them. If there is any other interest lemme know, it might help me try to convince them. It's just a small Porsche racing/performance shop down in SD but I know this car and have no problem approaching the guy and asking him at next event.

Tarett Engineering Competition Porsche Suspension Components

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wstar

I was hitting 1.2G fairly often in corners with no aero at all on my first weekend on real slicks, and spiking out further than that at times, in my datalogger. I'm sure you can go much further with a wing and a splitter.

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Dwnshift

So much depends on the 4 black rubber things that touch the road.
When we switched from Hoosier/ Contis to the Pirellis... We didnt have anything stiff enough on either end. (Bars)
And I can say this ... Our front bar with both of our "smaller" blades flat ... Is still stiffer than a hotchkis front.
And it was the first time we ever ...busted out the "big" rear bar...

BGTV8

But the Hoosier/Conti were about ~650mm dia and the Pirelli's are 680mm dia, so could it be that the diffference in a baggier tyre (taller sidewall and possibly substantially different construction) means more suspension effect in the tyre and you need to run a much stiffer setup on bar to take account of it ??

Dwnshift

The taller sidewall meant the acceleration sucked. The Contis are basically 450 mm sidewall vs 680 on the Pirelli.
It was horrible... That alone cost us about .7-.8 a lap.
In the Carousel we were up 3mph+ rolling speed through the corner... And going into turn 1 we were down 2 mph with earlier full throttle application.
At the end of the main straight we were down 500+ rpm.
The construction of the tires are completely different its apples to oranges...Conti/Hoosiers are a DoT and Pirellis are a full blown GT slick that produce way more grip.
When the tires grip as hard and as fast as the Pirelli dies..whatever roll you have is enhanced and happens instantly.
Also keep in mind we ran oem Nismo aero... And at this stage I wouldnt even consider a rear GT style wing.


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GSS138

The one number you can never find, the actual coefficient of friction on any given set of tires! It's a mystery. Back in the 80's in the Indy/Cart series, there were actually 3 spec tires. The manufacturers used to pick the rubber tread goop off of their tires and send it back to Akron for analysis. They didn't know which samples were which, but they knew which ones weren't theirs.

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FL 4Motion

I'm a little intimidated to even ask a ? In this thread but I figure this is the brst place to ask so here goes...

Wife just got back from Roebling track event. Complained of really bad understeer.

Car is a nismo on oem suspension with oem sized tires 245/40 19 front and 285/35 19 rears. Wheel offsets are +22 front and +12 rear.

Goal is to have a neutral balanced car, not too loose and eliminate the understeer.

Tires are michelin PSS and car is semi dd so we will be staying with street tires so PSS, re-11 etc type tires.

Based on my feeble understanding from reading this, stepping up to 275/35 fronts and maybe also the Hotchkis front bar (keep oem rear bar) will be good first step.

Next year plan to upgrade to swift spec r springs and spl suspension components. $$$ wallet can only take so much at a time.

Also will be adding the quaife LSD next year prior to the spring upgrade.

martin82

Run a square wheel and tire setup first 18x10.5 w 285/35/18, stiffest sway in front softest rear is the best way to go with spl front and rear arms and a good track alignment

martin82

And on hankook rs3

Zoren 370

Very interesting thread with a lot of technical information.
I must have failed physics and geometry whats the principle behind keeping the front bars at the hardest setting and keeping the rear bar at the softest even so keep it with the oem bar.

My Z is currently set front and rear at the hardest setting with whitelines
Yup the car is bouncy and horrible to drive running on coils too.
Do i need to adjust the dampening or the preload of the springs in the rear?
Im at 25 clicks from soft to hard front and rear dampeners. My coils has 32 settings.

GSS138

Sway bars do a few things, some of them unintentional but strangely beneficial. But the number one purpose of them is to stabilize the body and keep it from "rolling" over-sloshing from side to side. Our car with a big ole V6 sitting up high is prone to body roll up front, requiring a pretty stiff front bar to tame it by everyone's account. Just the design of a V6 engine is inherently going to have a higher center of gravity compared to a flat 6.

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wstar

You'll see mentioned by some (I forget if it was mentioned in this thread) that in theory swaybars shouldn't be necessary on a perfect racecar. You'd just set the springs and dampers correctly to avoid the worst of the body roll, and you don't want the swaybar doing other possibly-negative unrelated things. The reason swaybars make so much sense on a production car in general is that springs which are hard enough to kill significant amounts of body roll are going to be way too hard for normal use, so the swaybar is making up for lack of spring in one particular area: body roll.

But then again, even on some dedicated racecar designs that aren't based on production cars, you see some version of a roll bar on one or both ends of the car. It does have its purpose in fine-tuning sometimes. It's usually not nearly as dramatic in spring rate as a production-car rollbar, though. But yes, on our car you apparently just can't ever adequately kill the roll in the front, so you need both stiff springs and a stiff bar up there to help bring it under control.

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Zoren 370

Thanks guys I wish I have all your technical knowledge is setting our Z.
But Im learning a lot from this tread.

GSS138

For street driving on that bar, just based on the numbers, I would probably go middle in the front, softest in the rear.

I think Martin has or had the whitelines maybe he can comment.


I wouldn't mess with the preload. The preload especially on a daily driven car is a good thing.

As for the clicks, tell us which coils you have. Also are you adjusting rebound or compression? There are 2-way and one way dampers. It sounds like you have one way, and most one way dampers are rebound only.

The basic way you tune compression vs rebound is this: Go full soft on rebound, and then maybe two clicks on compression. Drive the car.

If you aren't happy add 2 more clicks of compression. Drive the car.

Add 2 more, etc. Until it "feels" correct for you.

Once you have dialed in compression, do the same thing with rebound, until the car feels too "jumpy" or uncontrollable for your tastes.

If you only have rebound, then use the same Idea. Just start at close to 0, and then add a little at a time.

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FL 4Motion