I've read a bunch regarding spring rates, etc. It seems that most people recommend something like 600f 500r spring rates for AutoX use. However, I can't seem to find springs for a 350Z that are anywhere close to that...

I'm unclear whether "coilovers" are allowed, so I was looking for a separate spring/shock combo. I know that the front suspension is pretty much a coilover anyway, but it's confusing.

Here's the relevant text from our local ruleset for (T)BSP:

It looks like coilovers, because they allow ride height adjustment by altering the lower spring perch, are disallowed by this.

Here's SCCA's BSP text:
It sounds like this allows coilovers (in the front, anyway)...


So... does anyone know where I can find individual springs that fit the 350Z that get the spring rate higher than +10%? What about a place to order the spring/shock set from a NISMO 350Z (not the S-Tune shocks/springs, but stock springs/shocks from the NISMO Z)?

 

As you mention, the front of the Z is a spring over a shock or a coilover.

No coilover for the rear. Doing so would alter suspension geometry. OEM Spring and shock perches must remain the same.





And the S-Tune suspension above would NOT suit your needs? Why?

 

Those (your suggested rates) seem pretty aggressive for a stock valved stock (10 and 8.5 kg where stock are 6-7 kg depending on year). Not sure how long they would hold up and if they would work well at higher speeds. Let's see what the other autocrossers like.

 

Also, there are many places you can order a custom spring from, made to your request, SPL and Eibach are a few. But I'm interested in seeing what others say on this.

 

The thought would include replacing the stock shocks with Konis... Actually, if done separately, it would be shocks then springs.

(I know the following will likely make me lose credibility, but... FWIW)
In real life, I've got an 07 w/ 275s all around, Nitto NT05.

I set up in Forza 3 an analogue:
245s all around, best non-slick tire.
Cams to get 315 hp
set up adjustable suspension to have OEM camber, spring rate and ride height. I estimated the shock valving at about 3.5
Set up adjustable final gear to 3.3 (auto)

Test track:
Iberian - Mini course (roughly 34-38 seconds for stockish cars)

I saw a delta of at least 2 seconds with springs/shocks alone. That's beating my time for a same-compound tire Acura NSX (otherwise stock) on the same course.

Theoretically, that would be enough to be viable for trophying the local street-tire version of BSP with good driving.

 

I use DA Koni's on my BSP car, but with soft springs at the moment. Plan is to go to a 14k front 12k rear next year. I don't believe you need to retain the factory spring bucket in the rear.....not positive though. Betamotorsports would know for sure I'd imagine....may want to PM him.

 

I was under the impression that the rear springs for the S-tune were only about 400 lbs, which is actually lower than the stock rear springs for an 07.

Is this incorrect?

 

Remember that the S-Tune spring is a progressive spring. Yes it takes 400 pounds to compress the first inch. The second inch? Can not give you a number but know it is more.

On the street you get a relatively comfortable ride. Push the Z in the corners (autocross) and the spring rate increases considerably.

 

BTW, an STi with only tires beat my optimal 350Z time for that course... Maybe I should consider CS instead.

 

No mention of what kind of LSD. IMHO (and I put my money where my mouth is) buying an OS Giken Super Lock will help your course times much more then shocks and springs.

After that, go to 2.5" ID springs front and rear and then you can buy whatever spring rate you want, in 25 lb. increments, for $45 each. Also, buy the best shocks you can afford. Stay away from the majority of the JDM stuff because they generally have too much compression damping and some of the lower priced shocks have amazingly inconsistent valving from shock to shock.