Spring rate help?

wstar

Or they could go engineer us a rear bar option that was actually weaker than stock. Then the set would be worth it.

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7AT Track Car!
Journal thread / Car setup details

synolimit

Everyone email.

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13 370z-

GSS138

"Loose" refers to rear loose end-oversteer. I have noticed that in AutoX they tend to like it better and it definitely makes sense since they have to do a lot more dancing and sharp turns than us track guys. I have only done autox a few times and it's not my thing personally, but man you learn a lot about how the car behaves.

Megan, I will agree 1100 lb springs were a bad example above, but 5000 would cause the condition I was trying to describe-trying to demonstrate a point that there is a number, that all of the basics break down, and the problem exponentiates. With slicks and full aero, I can see 1100 being very reasonable on a 750 lb corner, especially at 1G.

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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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Journal thread / Car setup details

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.

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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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

GSS138

I give full credit to others on this one, but the quick fix for you would be to drop to 18" wheels and run the 285/18 square setup with RS3's. I did it per one of my instructors (martin), and I am pretty sure he did it per some advice from (clintfocus) whom is a really fast dude lol .

We like the RS3 out here because it handles the heat of our tracks. Nothing wrong with the RE-11 and people in colder climates seem to prefer it. Never used it personally, but on tires I sort of follow the herd and my herd picks RS3's in SoCal.

On the OEM suspension, I personally feel(don't know) that the Hotchkiss would be too much. I would suggest either the Stillen or the Eibach sways as a huge, but not overkill solution that are both fairly inexpensive, and will make a large difference. I am now running the stillen sways on OEM suspension(non nismo) and it is wonderful as far as I am concerned. I can tell that once I upgrade springs and dampers that it will be too soft, but it is still an enormous upgrade from oem for ~ 300 bucks.

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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