i wanted to post this in the track forum and not in the suspension forum..
The issue i have right now is this..
my setup
0 toe f/r
2.5 camber front 4 camber rear

running stance coilovers
and hotchkiss sway bars

255/35/19 / 385/35/19

right now... when i take high speed corners the rear end does not settle at all. it is very squirmy and i do not feel confident ....
any suggestions to get the rear planted better?

it feels like bushing flex or tire flex..

 

-4 camber rear?

Is that a typo?

 

385/35/19 ???? another typo

 

If she takes her thong off, things should settle down just fine.

 

^^^+1

 

well played sir.

 

lol

 

the 0 toe in the rear can do that...I run 0 toe in the rear for AutoX, but I have noticed that the rear end does not feel as planted/firm on higher speed corners (track speeds ~ 80+ MPH). IMO put a little toe in for the rear and that should help.

 

yeah, I run a little toe-out front, and a VERY little toe-in in the rear for that exact reason.

 

+1 WTF?

 

sorry guys...
-4 rear is not a typo
however the 385 should be a 285
i have a seperate set of springs that i might try on the rear..
right now its
12 / 8 full coilover rear
i have 6kg springs as well
also i am thinking of toning down the rear camber a bit as well as toning down the sway bar..
do you guys think i should do that or should i try 1 step at a time..

 

Basic rule of thumb is to go as soft as you can on all settings, then adjust from there..tire pressures, sway bars, springs, and shocks....


BTW: I run 3.3 deg camber in front, 2 deg in the rear...with RA1s and stock NA engine and Hotchkis TVs kit and that works very well for me on high speed corners
(and low speed, but a little "loose" coming out of slow corners under full power)

 

your rear toe is owning your buttcheeks right now! The fastest (most consistant) car is one with only a very slight understeer, so you can lean on it without doubting the balance at speed 100+, and use some trail brake to help the entry in slow speed corners. ultimately you can go just a touch faster with a loose car, but even schumi or alonso cannot replicate it lap to lap.

 

so... i am gonna swap springs and tone down the sway bar a little in the rear.
might also crank the sway bar up front...
and then go from there..

if its still pretty bad im gonna dial in some toe in for the rear..
Primary reason i dont like toe is cause it kills the tires a little too quick for my taste.. currently w/ the massive ammount of camber i have now and zero toe i have not work out the tires in over 2 years worth of driving. however i know if i went toe in a bit it would wear out a bit faster....

also has anyone really dealt w/ aero on the track?

 

um....... why -4 rear camber?! ride height too low?

 

-4 camber in the rear is the most extreme I have ever heard of. Probably looks from behind like a Citroen Diane with a dozen bags of cement, with comparable handling. You have your camber settings essentially "reversed" and it is going to make you squiggle all over the place.

Always remember that the way the car comes from the factory that it has a programmed under steer, which is very much the safest approach to take for a daily driver car and an untrained driver from the perspective of high performance driving. That is what 99.9% of the buyers and drivers are, even for something as zippy as the 350Z.

The reason of course is that if the car starts to lose control from exceeding the adhesion or grip of the tires to the road surface, an understeering car loses grip in the front tires and "pushes". The instinctive reaction of the untrained driver at that instant is to lift his/her foot off the throttle, promoting two instantaneous changes that improve the situation. The weight of the car is thrown forward, creating more downward pressure on the front tires to increase grip. The second is reduce speed, which reduces demand on the front grip needed to turn the car. The third thing which a trained driver will do is to straighten out the steering a touch to further reduce demand on the tires, then but that is usually not what the typical person does. (The typical person will also put on brakes, and that really shoves weight forward, but complicates the grip situation by using grip to slow rather than turn, and they also feed in even more steering, making it even more prone to slide or push.)

When you start trying to monkey around with the handling characteristics of the car to "improve" them, you must be careful about doing it responsibly or you can turn your car into a death trap. Small incremental changes in single elements is normally recommended. (So, unless you really know what you are doing, don't go fiddling with the sways, camber links, toe settings, and damper settings all at the same time and then rush out to the track and drive like you stole it, unless you are prepared for harsh outcomes).

Most changes directed to "improve" the handling of the car trend to reducing or eliminating the programmed understeer and moving the car to a more "neutral" handling balance. Some will go so far as to bring the car to a slight oversteer condition. But one must be careful here. The car's inclinations will vary.....at what speeds and corner radius lengths does the car shift its personality from under, to neutral, to over steering? And do you have the skill and feel to instantly understand and react correctly in fractions of a second?

Why is so much made of understeer being "bad" and oversteer being "good" by high performance drivers, and the undercurrent of "real" drivers wanting over steer and wimps being any one else (and don't fall for that for an instant!). One reason is that if you are driving FAST on a race track, definitionally at the LIMITS of adhesion, and should you understeer, you must follow the regimen above, even if only for an instant, of easing off the gas and straightening steering to regain grip, then with the recovery of control setting off on finishing the corner and getting back on the accelerator. You are definitionally SLOWING DOWN. You have reached the grip limits of your tires in that particular corner challenge.

By doing things to your handling PROPERLY you can reduce the onset of that understeer condition, and go FASTER through the corner.

On the other hand, if you oversteer you MAY be able to control the loss of grip in the rear, with a quick counter steer action on the steering input WITHOUT having to lift throttle, and you go through the corner quicker by being able to stay on the accelerator. But you have to know what you are doing and you have to do it INSTANTLY. Of course, if you are wrong, you will spin out butt first, or slide off the track. Your outcome options are not as potentially favorable as an understeering car. And on the street there would be more car to car contact than a pinball machine, especially in the rain.

Most of the people who are talking about this subject get too aggressive with their opinions. So just take it easy and be safe and approach it with respect for both the integrity of your sheet metal and the safety of your skin.

You could go -2.5 or even -3 in the front if you want more aggressive turn in "bite" and reduced understeer. Probably you should consider taking the rears back to a maximum of -2 camber, and frankly -1.5 is not bad.

"More is better" is not true in performance driving. More camber, more toe, more stiff sways, more horsepower, more whatever. They always involve a compromise. Horsepower you say? Not more power? Yes. That usually involves more weight, and heat, and both are nasty monsters. And they do not necessarily get you around the track faster. Driver skill, and handling, and reducing weight and heat, are your objectives......in that order.

Be safe. Be smart.

Cheers,
Ed

 

Fixed....

Nice write up.

 

Good correction! Thanks.

 

Before jumping into the aero part of your question, what are you thinking about doing with respect to aero, and why? Aero can have some profound impacts on your handling, and positively, but you really need to have the rest of your "act" together on handling before you start messing with it, and understand the tradeoffs. There are virtually no street scenarios at legal rates of speed and circumstance, that aero is going to be a benefit. So it is a track day only thing. Can you go faster with a good aero package? Absolutely. Can it slow you down? Absolutely. A big wing on the back that helps keep the rear down in the corners is like dragging a week's worth of laundry down the front straight. In corners of less than 60mph the returns are problematic as air flow is not sufficient to apply adequate downforce...so you need to adjust settings to the specific track to give "more wing" or "less wing" to your car. Then you have your front and rear diffusers, front canards, and of course the front "splitter". It would be a good idea to do some reading on the purposes of all of these devices and their applications to this car before buying and installing any of them, and to get a ride in a car with aero mods to see the change in feel as well.

 

For the basics, there's a good write-up on Monza versus Monaco setups on S14.net (E30 M3 forum). I'm too lazy to dig it up though.