Does anyone know the spring rate for an 05 coupe with the Sport Package? I did a search and there's nothing. I've ordered the Tein H-techs for the 350Z. I hope I'm not going to a lower spring rate since the 05 suspension is supposed to be tighter!

Thanks

 

I tried to do a post announcing that I now have the spring rates for the 05 coupe sport suspension, but the system would NOT let me create the new thread so I gave up.

Front spring rate is the same, rear rate is however much higher.
314/427

 

While you're at it, can you please post the previous spring rates? They've been posted many times, but this way they'll all be in one thread.

 

G35 coupe All with oem 17" & 18" wheels
314/342

G35 coupe 2005 with sport suspension/oem 19" wheels
314/427

G35 sedan with sport suspension
314/342

G35 sedan non sport
283/308

G35X
unknown

2003 and 2004 350Z* (built prior to 10/31/03)
314/342

*refer's to the rumor that all roadsteers and all Z's built after 10/31/03 with the revised suspension feature rear spring rates that are higher, specific number as follows. Attempts on my part to get anyone to lend me a single rear Z 2004-2005 spring has thus failed, so we continue to not really know one way or the other. The only reason I have 05 G35 sport coupe rates is because a member here lent me his springs to test.
2004-2005* 350Z & 350Z roadsteer
314/417

 

Gsedan35, thanks for the info. I think what I'll endup doing is install the 350Z H-techs on the front and leave the OEM springs in the rear. I'll cut the upper spring mounts to your method to lower the rear. If I remember correctly the drop is 0.75" once the mounts are cut, right?? This way I can have a spring rate of 358 in-lbs in the front and 427 in-lbs in the rear. This should give me an overall drop of 0.75" front and rear. Has anyone else with an 05 sport suspension experienced this?

 

Keep in mind guys, that while the G35 and Z have relatively high rear spring rates, the spring mounts on the suspension arm. The actual rate at the wheel will be less. I don't know by how much, most multi-link suspensions run a coil-over set-up that attaches to either the spindle or the suspension arm near the spindle. The wheel rate in this case will be closer to that of the spring rate than you will find in the G/Z. If, for example the spring was mounted halfway between the suspension mounting point and the wheel, rate at the wheel would be 50% of the spring's rate. Consequently, the increase in rate at the wheel from the stiffer spring rate would also only be 50% more. So before you start mixing and matching, make sure you understand what you are actually doing...

BTW, the 50% is only an example. I do not actually know the spring position relative to the suspension arm length.

 

I don't post data on motion rates or wheel rates because I do not want to over complicate things and then make a bunch of confused members. But since you've brought the subject up. And let's face it, the first time I posted motion rate numbers, I had the front number's all wrong. That's been fixed.

Their are only 3* known coilover systems for the G and Z that actually run the rear springs on the dampner body, and they all run springs in the oem rear location as well, so a total of 4 springs in the back. They are, Buddy club, Kg/Mm, and Top secret (Agosta). *The upcomming Truechoice/Unitech coilover system may use rear dampner mounted springs only, only time will tell.

All other coilovers do not run their rear springs for this platform on the rear dampner body, they use the oem location only.


Motion Rates G35/350Z (for calculating wheel rates)

Front: .53 then multiply answer by .96 to correct for 10 degre mounting angle of front shock/spring assembly (consistent from normal to full compression)

Rear: .36 (.59 on any system that run's spring on dampner body)

Knowing the motion rates and theirfore wheel rates does not change any spring rate data that I have posted. Percentages of increase or decrease in stiffness do not change, nor does percentage of roll stiffness transfered to one end of the car. As a example, let's pick on a system known to transfer a lot of roll stiffness to the front of the car.

This is how said system differs from a oem car running 314/342 spring rates or 160/123 wheel rates

Zeal function V6 coilover
Spring rates 560/448
Stiffer then oem by F+78% R+31%
Transfers +47% roll stiffness to front

Same, converted into wheel rates vs oem wheel rates
Zeal function V6 coilover
wheel rates 285/161
Stiffer then oem wheel rates by F+78% R +31%
Transfer's +47% roll stiffness to the front.

Getting back to the 05 coupe with the sport suspension, Infiniti's increase of the car's rear spring rates, net's a 25% increase in roll stiffness in the rear. I only would have tired 10% to start out with, but hey thats R&D for ya.

 

Jim, thanks for the '05 Sport Coupe spring rates. I'm surprised that they upped the rear rates by as you say 25%. That's pretty damn signficant. This piece of info comes in handy on my quest to find linear springs in the 400-500 lb/ft range and which will not drop my sedan more than 1".