Definitely balance wheels - a wheel 50 gms out at 250kph will shake the filling out of your teeth.

In the new Camaro Z28, Chevrolet marketing got some mileage out of how they're texturing the wheel bead surface to keep the tire from rotating too much on the wheel:
Camaro Z/28 is so grippy GM had to find way to keep tires from slipping on wheels - Autoblog
In reality this sort of thing has been happening on hard-driven cars for a long time. So if you have a tire-based imbalance, there's not much help in balancing if you have sticky tires you'll push hard.

An inherently unbalanced wheel, I suppose it could help, but balancing isn't usually done that way, and the tire has a much greater impact on the balance of the overall package.

But to each their own...

On slick I wouldn't run anything lower than 900 *16kg* in the front !!
Now with the aero its an ever bigger number !

as far as running an 1150+spring , Its not un-commun to see a car which can be Pro or Amateur driver with nearly as much spring rate and they wouldn't go much below than this with slicks.

and remember that 1150 spring on a 750 corner, Im pretty sure the car is moving and seeing over 1g in the corner.. isnt that bring that corner to over 1500 llbs ? then you have 1inch and half of travel due to weight transfer.. which is relatively acceptable in my book for 1g corner.

math paper talking is quite different when you are actually driving the car, it will bring you close but the rest its all feeling and how the car react.



http://www.the370z.com/members/wstar...sr-houston.jpg

I haven't gave my opinion on the first picture Wstar posted,
For his setup I would recommend 16kg *900* front // 12kg *672* rear with the stiffer front bar and then the stock rear.

this is my new baseline w/ aero I will be using when I'm fit enough to get back on the track. I know the front wont be enough but its a baseline.

For you guys who like "loose" cars what does that mean?

I like a balanced car that transitions well and is getting maximum mechnical grip from the tires. Not too much understeer and not much oversteer so I can managing turning with brakes and power application. I havent found too many road courses or hillclimbs where excessive oversteer is benificial .

So isnt what somone who is going to track wants is nuteral handling car with excellent transistory response for given tire selected? All this focus on loose or not loose seems to be foreign to me. Focusing on what spring and bar combo can slightly increase or decrease understeer and oversteer to your liking is probably better focus. Loose car as I know it isnt fast. But then I have been in very well buttoned down race cars with huge spring rates that arent "loose"

Loose, in this context, I think, just means a tendency towards oversteer. Not the kind that will get you in trouble with big snap oversteers, but just a enough tendency that it's easy to rotate the car. I like how the car feels that way. I don't know if it's a fundamental thing that, given a perfect driver, either a loose or tight car setup is actually faster. But at least for me, being a bit loose is easier to feel and control at the limit with steering and throttle corrections, and it's easier to get the car to rotate through tight corners (both under trailing brake at the start and under throttle as you come out).

^ I should add to the above, I think there's a distinction to be drawn between ideal situations and the real world, too.

In an ideal scenario, the pavement is perfect, there's no surprises from traffic or turtles or mud clods, I hit my reference points at precisely the correct location and speed every lap, and nothing about the car changes over the course of a session (e.g. tires warming up). If this were always the case, my inputs would always be perfect to keep the car exactly where it should be at the best slip angle for traction, and the car would always naturally track-out to the correct point at the end, etc.

In the real world, there are too many variables to even try to list, all the time. If you're consistent you've eliminated a lot of variables, but millisecond-by-millisecond you're making small (and sometimes, large) corrections to your inputs to account for all these variable things coming into play. Many of those corrections get to be a subconscious thing over time - they happen way too fast for it to even be possible that you're consciously thinking through the decision process. Either that or you drive slow enough that most of these variables don't actually matter because you're not that close to the edge.

I think when you're out there in that mode, near the edge, where you're constantly making corrections to keep the car where you want it to be and not flying off the track just because you happened to hit a blade of loose grass or dropped a couple wheels in the dirt to avoid traffic, a loose tendency is easier to control than a tight one (at least, it is for my brain, and it seems like it's not uncommon to feel that way).

Reading all this WTF Hotchkins? I emailed with no response awhile ago. No one wants their rear bar is seems or have to pay for it. Do we really have to buy both and trash the rear? No ones going to just buy a stiff rear bar and I don't want to screw someone just selling it to them and being like "you need this." If we pay almost $500 for the set I'd rather pay more money for just a front that's bigger and better.

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

Everyone email.

"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.

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

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.

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...

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 ??

Spring rate help?
 

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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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.

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.

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

And on hankook rs3

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.

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.

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.

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

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.

Any inputs on my suspension plans? Thanks
 

:tiphat:

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.

Here is another bit... If you dont have adjustable front arms... You will need BAR.
:)
There isnt a lot of grip on the sidewall of any tire.
Just sayin.


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Sticking with our super laps. At least for now, not going to drop down to 18s so closest to "square" setup will be to run the 275/35/19s up front.

Currently on PSS and happy with them so far. If wife wants stickier tires I will def look at the rs3s

Are you suggesting keeping the stock rear bar and upgrading the front to the stillen or eibach set full stiff I'm assuming?

The outside blocks on the drivers side front tire are toast after Roebling. Very outside edge is just worn completely.

Run the front of either brand at full stiff, with the eibach(don't know for sure maybe medium on the rear), on the stillen stay softest in in the rear.

The point is that both at full stiff are very close to about as stiff as you can go on OEM setup. Any stiffer(Whiteline or Hotchkiss or Doran's professional bar) is probably too much for oem dampers and springs. It's all about balance and is all relative.

It's like asking if an Olympic boxer is too tough to fight your little brother(OEM) or if an Olympic boxer is tough enough to fight Pacquiao(racing suspension).

worth downgrading to 18's just because of saving the $$ on tires alone, for example rs3's in 18's my hook up is under $900 but a set of 19's it's close to 1200. So after about 4 set of tires your savings is exactly 1 set of nt03 enkei 18x.5 wheels.

That makes sense. :tup: what about with swift spec R springs which I'll be going to down the road. Would the stillen bar be enough or would I need to upgrade to whitrline or Hotchkis at that point?

Spec r's are a mild but very good upgrade as well. You are still within the OEM spec, but probably will want to upgrade your dampers to Koni yellows. Again another huge but very affordable upgrade in the street/track range. If you are going to look at swifts+konis, then you should definitely consider the KW one way setup as well. Both are very good in that price range. It sort of comes down to preference at that point. KW has some advantages in that the fronts are ride height adjustable coils which help with corner balancing, but me personally I hate the damn colors of their stupid springs so would buy the Swifts and Konis lol.

I priced the square 18 set up compared to my current 19 setup and it's no cheaper really on tire rack. Going to 275/35/19 up front might change that but I don't have a "hook up" on tires so I'm paying retail.

At this point even though I know 18 are "better" for the track I'm not going that way yet.

Lol at hating the colors :icon17:

I'll most likely go with the swift/Koni yellow combo as it's a set it and forget setup.

Goal with this car is to keep things simple even tho I get that we're leaving handling on the table so to speak it will still be a big improvement over stock

well shoot me a message, I dont pay ANYTHING retail LOL

Yeah I didn't even understand why martin liked the damn KW, and he didn't understand why I hated it, and then I told him it's the colors, and then he said "Lakers Bro". And then it made sense to me.

18's are the way to go for affordability in tires. The price is honestly 100's of dollars difference as martin pointed out and there are many more options with a 18" wheel. It also improves your acceleration as the drag strip guys know. I run 19" Foose "Bling Chrome" wheels on street 1 because they look nice, but 2 I would be at a disadvantage on track. If you want to see the real problem browse the GTR forums where they all have 20" wheels. There are no tire options for those guys besides the toyo R888. They have one friggin tire option in that size. (maybe soon they will have the NT01)

With an 18" wheels your tire options are 10 fold at least.

And yes, if you were potentially in need of tires, then talking to the owner of a car that one of hankook's sponsored drivers on this forum owns is mutually a good idea.

Ps I do not run kw v3 lol

Yeah I had that problem for a while too, I'd just destroy the outsides of the front tires while leaving the inner tread looking new. More front camber! (and caster if you can)

Thats the truth. Im loving my SPL front arms! No specific race slick setup tips for us (spring rates used, bar sizes, alignment settings?) :hello: