Thanks cwmizner, but I guess what I meant to ask is really how much.
I'm new to getting into suspension drops and such, so please bear with my newbieness.


2004 G35 sedan. Silver/graphite, Premium, sport, aero package. Z-tube, K&N

 

sorry for being a smart *** bro, my bad...

Mize
Silver 03 6 Speed Sedan/Willow/Premium
http://www.AutomobileFanatic.com

 

No big deal.
I am just wondering how out of spec the new springs put the camber, and if you can get it all back. And if you can't how will that affect tire wear and such.

thanks
mike

2004 G35 sedan. Silver/graphite, Premium, sport, aero package. Z-tube, K&N

 

Performance in what sense? I autocross and was just about ready to get these springs. Ran it by some VERY fast autocrossers (national caliber) and the were very adamant about shifting the spring bias to the front...

how big a deal is this linear vs. progressive thing?

 

bump, anyone know if GSedan35 is still around much on this board?

 

He's still around.
PM him here

 

Well, even my advice should be held against the findings of your own research. Which is why sometimes my post's may have a little too much info in them. I want to provide as many data hard points that I can so those that might be driven to do more research will be armed with what they need to know to make better more informed choices.

What comes to mind if I heard those guys talking would be this.

1.How much roll stiffness do they propose to shift to the front?
2.What are they driving?
3.What setup do they have?
4.Do they know the oem spring rates?
5.Do they know the oem wheel rates?
6.In saying what they said, what were their times when trying differing spring rate biases?
7.Did they get caught up in working around inferior oem parts rather then following proper tuner setup and using the right aftermarket parts?

Shifting of roll stiffness to the front is a known tuning baseline to reduce oversteer. If applied to a setup that already understeers it will make the understeer worse.

In a discussion like this it's important to realize that the rear springs due to their inboard location do not leverage as much force to the wheels. This is why the oem spring rates are higher in the rear.

Let's look at two setups and see how much spring rate actually makes it to the wheels (wheel rate).

oem wheel rate G35 sedan with sport, G35 coupe without oem 19's, 350Z
156lbs/123

Tein H-tech G35 coupe/sedan
161/94

RSR 350Z
172/150

Wheel rates for the front of the car can be found by multiplying a springs rate by .53 then by .94 for angle correction. In the rear multiply by .36.

Progressive springs are a compromise, trading ride quality or adapting to poor oem shock performance for less performance. They will allow for more weight transfer issues(turn in dive and squat) and the likelyhood of at the limit issues because the outside wheels are on differing spring rates. The car can yaw on those differing rates and make mid course corrections difficult as a result. Progressive springs can be made to work in very limited conditions where the parameters are well known, like a specific road course where telemetry is constantly giving feedback to help select the right rates.


Eibach G35 Sedan
259/334 front 359/413 rear
Looking at peak rates and in comparison to a sport suspended sedan)
F +6% R +21%

Looking at peak rates only and in comparison to a non sport sedan)
F +18% R +34%
Spring stiffness to oem as seen in a right hand corner because of the progressive spring rates, on a linear spring system, like the oem setup use’s, you would NOT see a difference left to right. (reverse for a left hand corner)
RF -17%
RR +5%
LF +6%
LR +21%
Side Note: The sedan Eibachs were developed on a non sport sedan, they did not use a sport suspended car to do the R&D work.

Eibach G35 Coupe progressive springs
229/337 front 274/463 rear
F +7% R +35% (looking at peak rates only)
Spring stiffness to oem as seen in a right hand corner because of the progressive spring rates, on a linear spring system, like the oem setup use’s, you would NOT see a difference left to right. (reverse for a left hand corner)
RF -27%
RR -20%
LF +7%
RR +35%

 

With all this information flying around, and from reading most of it, I personally have decided one thing. It can make your brain hurt.

I will probably never track my car, 04 sedan, but will always enjoy a nice curve on the road.

I have gone back and forth on different springs, shocks, coilovers, and everything else that goes along with it. And you pretty much need to decide on what you are going to be using the car for.
If you want to just lower the car, get springs; but then you run into camber issues, but those can be remedied. But you will lose some cornering abilities.
If you want to track, after market springs and shocks will help. With full coil-overs probably providing the best solution, but you lose ride quality sometimes with this route.

Please bear with me....I am still learning all of this, so the above information was what I have gotten so far, in lamen's terms.

Me personally, I am going the 350z suspension route. From reading and researching, it offers the drop I want (about an inch), and will defnitely increase the response and turning ability of the car, and will not hinder ride performance all that much. Plus, I can find a set for basically nothing, and put it on for next to nothing.

If I were planning to solo the car, or maybe take to the race track the car all the time, I would definitely go another route. Like I said....it's all about what you want to do with the car.

just my .02
mike

 

Makes sense to me.

A couple of things to know about with the oem 350Z suspension. Avoid 2003 setup's at all costs. If buying a 2004 or 2005 setup you MUST confirm that the shocks are actually revised shocks as some 2004 Z's were actually equipped with 2003 shocks, pm me so you can have the part numbers so when you ask the seller what shock part numbers he's actually selling. Even with the resived 2004 Z shocks, ride quality is firmer then the sedan oem ride. Also, recent transaction prices as in street prices of 2004 350Z suspensions has dropped to as low as $150/$200. I tried to buy a setup recently on my350Z.com for $160 shipped, but lost out to a local buyer.

A even better choice would be oem Z springs with Tokico D-specs.

 

Thanks for the replies Gsedan35! My 'fast' autocross guy was just making a general comment. His feeling is that with a 'stiff' rear setup, with my KAAZ LSD, for autocross, that it will be difficult to put power down and the car will be a handful in fast slaloms for example. His thought is that understeer isn't necessarily an evil for autocross; he'd rather lose a little time in a slow tight turn due to understeer vs. losing a lot of time in a fast slalom because of oversteer. Makes sense to me and the boy is FAST (I let him drive my car once and it was humbling, but good learning experience as well).

Other ‘data’ I’m considering is a guy that autoXs with us in a G35 coupe. He’s got Tein Flex coilovers with ‘square’ spring rates (~670 both front and rear) and his car was in fact ‘incredibly lose’, he completely disconnected his rear sway and saw a 40, yes forty point PAX improvement over his last 3 events, granted tons of other variables involved (alignment, other mods, etc)

I particularly appreciate your explanation on progressive vs. linear and the info that stock sedan/coupe/350z springs are all linear as well as the RS*Rs. To me seems/sounds like a huge deal considering my autoX aspirations. It seems spring manufactures are catering to those that want the look of a drop but don’t want to negatively affect ride quality too much.

Also saw your post to my related question on springs. Re: bushings, need to check into what the rules allow for STX…

So seems direction is:

1. go with the 350z rs*r springs and compensate for oversteer if it exists with other tuning methods
2. go with stock 350z springs, same comment on tuning
3. ship my Konis to GC for coilover conversion and start playing with spring rates/ride heights (we haven’t even talked about optimum ride height and affects of lower front relative to rear and visa versa)


#3 seems the most flexible, but probably most costly and time consuming as well

All a balance and personal choice…

Good stuff, thanks again!