Just wondering if anyone knows for certain what the OEM and Nismo spring rates are.

I found OEM rates posted as 347 lb/in front and 419 lb/in rear. Can anyone confirm that is the correct OEM rates?

Does anyone know the spring rates used in the Nismo S Tune setup?

BTW divide by 5.59 to get kg/cm correct?

Anyway now that my exhaust is here I'm turning my attention to suspension. As my car is on the street 99% of the time I don't want anything a lot stiffer than stock but would like adjustability for initial tuning so I'm considering the Cusco coilovers and sways. I read somewhere (that I now can't find) the Cusco spring rates are 559 lb/in front and 391 lb/in rear. I'd like to see how much stiffer that is to the S Tune setup. As you can order other spring rates with the Cusco I may go for something a little softer than their standard spring.

 

I'm the one that posted those rates. I got them by taking many different measurements on a set of stock 350Z springs I own. I measured the diameter of the wire used in the spring, inside width of the coil's in the springs and the number of active coils. I then took that data and sent it to a engineer friend of mine and he worked the math for the spring rates. Some things of note: I was told that the G35 and 350Z spring rates are the same. Using this system proved this to be correct. In spite of the fact that the G35 sedan uses a taller spring with a slightly different wire diameter, Nissan did indeed make them the same stiffness. Also these spring rates almost exactly match the peak spring rates on all the Eibach FM spring applications and are within a couple lbs of the RSR down springs published spring rate for the 350Z.

The formula to convert a spring rate that is listed in Kg is 1 Kg='s 59lbs.

One big difference between any coilover system and the S-tune system is that the front springs on the S-tune are progressive with linear in the rear. All coilovers should be linear, the use of tender springs is not a different form of progressive spring action, btw.

Have you gone and read some of the posts made my people whom are reporting new install experiences? What have you read that makes you think the Cusco coilovers will out perform the others? I think it's tuff to make a purchase decision on coilovers. Yes we have a number of S-tune, Tein, HKS, and Jic owner experiences. But what about the one's that I haven't seen someone talk about. "Might" they actually be better? In any event I think the Tein flex system has by far the most influencial owner feedback, IMO. I like the idea of Tein SS coilovers ordered with 450lbs spring rates myself.

I did find a site that had the Cusco coilover spring rates, I'll have to try and find it. If you find it before me, please post the URL.

 

Here's a link to the HKS Hypermax coilover spring and damping rates...
http://www.350tuner.com/hks.htm

Here's the spring rates for the JIC FLT A-2 coilovers...
http://www.splparts.com/Z33/Suspension/Coilover.asp

How about the Cusco Zero-1 and Zero-2 coilover rates (they're the same)...
http://www.i-m-racing.com/cuzeco351.html

Most everyone else seems to want to keep their rates a secret...

 

Thanks Gcoupe35 and TereP

I've read a lot of user experiences from this board and think all of the products would be OK although some of them are geared towards the track too much for me. I want to bring the handling back to neutral without sacrificing too much in the ride.

The S Tune looks like a nice simple and relatively cheap option for the street. I'm considering the Cusco Zero2R because I've used their products before and I can get them cheaper than the other coilovers.

I'm also a believer that the Cusco coilovers must be used with the Cusco sways. If you look at most setups the front and rear spring rates are fairly similar but the Cusco ones the rear is a fair bit softer than the front. Then look at the Cusco rear sway at 73% stiffer than OEM. That's the stiffest rear sway I've seen for the Z and I believe it's because it's been tuned to work with the softer rear springs.

There's no arguing the Tein are a good setup with a lot of positive feedback on this site alone but that doesn't mean everyone should use them without even considering other options. Variety is good I'm yet to make a decision and the purchase is a few months off so I'm only just starting my research.

 

Actually, the biggest difference is that the spring rates on a coilover really are not comparable in any respect to spring rates of lowering springs alone, as coilvoes come with dampers as well, which are valved correctly for the srpings they come with.

The only true fair comparison is various aftermarket lowering springs to one another, assuming they will all be used on stock struts. You cna get very techincal and say that altering wheels will also alter the overall rate of the springs (due to where the new whels sit, it may increase or decrese suspension preload, but lets skit tht for a second