Didn't find a useful comparo doing a search... I'm interested in amount of drop and increase in stiffness between the Eibach Pro kit and the stock sport suspension (as opposed to the stock non-sport suspension)

Is it worth the change? I have the sport suspension but I'm looking for less roll and a slightly stiffer ride. Would this be the way to go? Would I be better off sticking with the existing springs and adding swaybars?

Any advice appreciated. Thanks in advance.

BTW, how do I tell the difference between sport and non sport springs on the G35? I remember reading that the sport springs are a different color but mine are black, I'm pretty sure. 2004 Sedan.

 

this is an interesting question and i would like to know as well. i think that the sport suspension handles nicely especially over non-sport, but the wheel gap is pretty big. i would hope that the pro-kit would mean even better handling without sacrificing too much ride quality. i think the ride on the stock sport suspension is already a little harsh for a luxury sedan

 

Not sure if they changed it for the 2005 Sedans, but on the '03 and '04 Sedans, the sport suspensions used red shocks while the non-sport were black. I believe all the springs were black regardless.

As for the difference between the Pro-Kit springs and the stock sport springs here are the facts...

Pro-Kit is a progressive spring, oem spring is linear
Pro-Kit has spring rates of (first number is intial/second is final): 229/337 front 274/463 rear
OEM Sport spring rates: 314 front 342 rear
Pro-Kit springs for the sedan will drop the car about -1.1 front and back

If you are looking for better performance, I would say the Pro-Kit is not the way to go due to it being a progressive spring and having very soft intial spring rates. I would only get the Pro-Kit for comfort or appearance reasons.

Here's a good post by Gsedan35 explaining progressive vs linear springs.

Click Here

 

i just thought about something....what about pro-kit springs meant for a 350Z?

 

dklau, thanks for pointing us to that post, and for the info YOU provided. Very very useful stuff.

So, what's the alternative? Z stock springs? Some other after market spring for the Sedan?

The Teins for the sedan look to be linear but the rear springs seem to be softer than the stock sport springs. (h-tech 325f/263r and s-tech 358f/274r based on data from performancenissanparts.com) ...Not something I'm really looking for.

The Tein-S for 350Z however, look like they're 386f/402r but I don't know if we can simply use those on our cars.

Also, back to the original question, would simply adding sways help with roll? Seems like my car rolls more now than it used to but I'm sure springs become fatigued over time. I'm at 30k miles.

...I've also had loaners with non-sport that just feel SO much 'tighter' than my car. I'll look at the shocks later and see what color they are.

 

Yes, the H-Techs for the 350Z are a good solution for the sedan. But I would not pair those with the stock sport shocks. They are already underdamped to begin with and control would just be worse with the stiffer springs. My suggestion is to get them along with Tokico D-Specs, Konis, or if you want a more budget concious solution, used OEM Z shocks, preferably the revised ones. The Hotchkis or RS-R springs wouldn't be a bad choice either but the drop is more significant. Here's some info posted by Gsedan35 and some additional notes.

Tein H-tech 350z (fronts are progressive, rears are linear)
358/375 F+14% R+11%
Transfers +3% roll stiffness to front
Drop on a sedan would be around 1.2"/1.3"

Hotchkis 350Z springs (linear springs)
340/330 F+8% R-3%
Transfers +12% roll stiffness to front
Drop on a sedan would be around 1.5"/1.6"

RSR 350Z springs (just a wee bit progressive F&R, maybe one coil is progressive)
345/417 F+10% R+22%
Transfers +12% roll stiffness to rear
Drop on a sedan would be around 1.6" front and rear

Simply adding sway bars would help with roll but the main thing you should use is springs first and then sways to fine tune. It's no big deal though so get sways if you want. Just be sure you get adjustable ones so you can fine tune to your needs.

 

Here are spring rate specs of the different Pro-Kit springs posted by guess who, Gsedan35. Take what you want from the info. I believe the problem with the pro-kit springs in term of performance is that a good portion of the spring is progressive and takes a bit of compression before the linear part takes effect.

Eibach's as noted (first number is the softer initial rate, followed by the higher final rate)
350Z 296/384 front 316/421 rear
G35c 229/337 front 274/463 rear
G35s 259/334 front 359/413 rear