Hey everyone....I've been reading around the board regarding springs and spring rates...From what i gather is (correct me if i'm wrong) the higher spring rate the stiffer they are? Is there more to this that i should know? Eventually, i'd like to afford some 19's and lower it with the OEM 350z springs. I've read it only lowers the coupe 1/2" which is fine by me. Can I just install the springs or does it have to be the entire suspension? I'm not entirely new to lowering as i've owned a lowered vehicle before i'm just new to the technical aspect of it. Thanks for your help!

 

Oem 2003* 350Z springs have the same spring rates that your coupe has right now since you don't have a 2005 coupe with oem 19's. You will get a 1/2" drop and you'll be using springs that are no stiffer then what your current shocks are dealing with. Are the oem shocks really fabulous, no not really, installing Tokico D-specs are well worth the money even with oem spring rates.


*Avoid 2004+ oem Z springs because they have a much higher rear spring rate that your oem shocks will choke on.

 

Thanks Gsedan for the advice!!! If anyone has input please post!

 

Can you use the 2004+ springs with Tokico D-specs? Any idea of ride quality and roll stiffness?

 

Wait. So the 2005 g35s with the sport suspension package have springs that are stiffer than on an 03z? Cuz I test drove an 04 350z and I thought the ride was significantly stiffer and rougher than on an 05 g35 with sport. Is it the additional weight of the G that makes the suspension feel softer? I mean it only weighs 200lbs extra.

 

The Tokico's are double adjustable, so you can have a hand setting up the car's ride quality. The stiffer rear springs will give you more rear roll stiffness, though I recommend installing adjustable sway's so you can use them to set the car's balance to be just the way you like it (or the way your setup and skill level like it).

 

No the sedan with sport has springs that are the same stiffness as oem 2003 350Z springs. I was talking about 05 coupes with oem 19's, they have stiffer rear spring rates then the 2003 oem 350Z, +24%.

Your 04 Z test drive makes perfect sense. The Z suspension uses much stiffer shocks that make the car feel as if it has much stiffer springs. But, take a long corner, on that get's past shock stiffness and the springs will reveal themselves with the same amount of body roll in the end, the stiffer shocks make getting to that point take a little longer. I used to have a oem 350Z suspension on my sedan.

 

So if you are going to go with the Tokico D-specs, is there any preference between the 2003 350Z springs and the 2004+ 350Z springs? There seems to be lots of the 2003 version out there at a good price but 2004+ springs have a premium price.

 

Well since the D-specs overcome the problem with running the stiffer rear 04+ oem 350Z rear springs with the oem sedan shocks it's up to you if you want the stiffer rear springs or not. I would be more inclined to do the stiffer rears if I had adjustable sways on the car or I planned on getting them near the time of the shock/spring install.

I bought my set of 04+ oem Z springs to test how the higher rear rates will effect the car, but it will be awhile before I get them on the car, I have other things going on suspension wise that I need to wrap up. And in my case I would not be going from a 342lbs rear rate to 427lbs, I'd be going from 375lbs to 427lbs.

 

Sorry. I was talking about the same thing. I know I was a bit misleading by typing G35s. I meant G35s as in plural of G35 and not G35 sedan.

But I understand now. Shock valving being different on the Z than on the G. Forgot to take that into consideration.

 

Going from 314/342 to 314/427 adds 24.8% roll stiffness to the rear. What kind of effect would you expect this have on under/over steer? Or am off-base with this and the under/over steer has more to do with the sways.

 

Going 25% more roll stiffness in the rear will definitely promote more oversteer whether it be springs or sways. How much I'm not sure as I don't how much of that percentage increase actually makes it to the wheels (wheel rate). Gsedan could answer that one. I believe though the sway bars have been altered with the cars that have the 427 rear springs.

 

I would expect the car to have less push or understeer. But you can also expect the chance that you will also have less traction coming out of corners. I believe that the car's that have the 427lbs rear oem spring rates have stiffer front sway bars. Their are a couple of people on my350Z.com that this is the case, even going as far as to say they car's use a +17% to +20% stiffer front bar. Remember, we do have member's here with oem 2005 350Z suspension's installed on their sedans. But, I do not know how much at the limit handling evaluation they may have done.

In the end how things are supposed to behave might be what happen's. That's why I've run several different setup's on the car, of course it helps that I have the willingness to turn a wrench to make it happen, but the car is kinda a hobby for me too. I must say I was suprised then I did the 350Z H-tech spring test with oem sedan sport shocks. While the ride quality was actually very nice, the shocks came up short, felt like they didn't have enough rebound control most of the time. But the suprise was the amount of pull I had in corner's, it was actually really good, better then any other setup I had run prior. Had I not been willing to test, I never would have found that out.

 

Question for Gsedan35: I assume that your 350Z Tein H-techs would lower your sedan about 1". Were you able to set your camber to spec without using adjustable A-arms? Also, do you know if the TrueChoice/Unitech suspension can be used on the sedan? Thanks.

 

I can't answer the question because I never did bother to get the car aligned. Originally I had planned on getting a alignment, but in the end I was satisfied with resetting the rear camber and toe since I was only going to be on the setup for a short time.

The H-tech's will drop a sedan on oem sized tires about 1.4"/1.3". Given that on a 1" drop my alignment specs were,.... Front camber -1.1/-1.4 and in the rear I had the shop set me to the MOST negitive camber the oem system would give me and still have a small amount of rear toe in, -1.3.

I am currently on a setup that has the exact same drop as the 350Z H-techs. But I'll have to wait for more parts to arrive (it will be awhile I'm afraid as I'm working around my wifes "mod" radar). Once everything is in place I'll align.

The Truechoice/Unitech setup will fit on the sedan, but I would wait for a few things to be resolved for a couple of Z guys that have the setup, their is a thread on my350Z.com that I'm following.