Changed my DSpec setting to F:3.5 / R:4.0 tonight (from F:4.0 / R:4.5)
and took it out for a spin. It's still comfy but getting kinda close to 'stiff'.
Still absorbs bumps well, but initial bump getting a little sharp because
of the 35-profile S03's.

Considerably flatter through the turns from F:4 / R4.5. I don't think I
would set it any stiffer with these springs...kind of borderline comfort.

Stillen sways set F: soft / R: med

 

KenChan:
I have the Prokit w/ stock struts on my '04 G35x. You may recall I trimmed the bumpstops this Winter per your advice, and that really helped. However, now I have my summer 20" on, and the ride is just horrible due to the soft standard struts. What do you recommend?

1. Keep the Prokit and replace struts with D-specs (which one should I get? for coupe, sedan, or 350z)
or
2. Swap out the Prokit and stock struts for 2004+ OEM 350z?

Thanks,
-Ken

 

pimpinG- You might want to do some research first to see if the 350Z stock setup
fit on your G35x. if it does, that might be a better setup than going with D-Specs
on your Prokits in terms of performance..but honestly, if I was you, id give the
D-Specs a try on your current setup. First because you already have half the
setup, have use the springs for a while and broken them in, you know how the
car behaves and its problem areas right now... when setting up a car it's easier
to setup one thing at a time while keeping the other components constant.
If you're not satisified with the ride height, perhaps you might want to
just swap out to the 350Z setup if they fit your car.

Having adjustability imho has much more advantages than given only
one setup where you can't adjust to your preference... what if you do the
350Z and it's too firm or too low, or, etc.? If you have the money and time
to experiment, I encourage it...but, if not and you're happy with the current
ride height just do the D-Specs (D-specs are not height adjustable)

Unfortunately, I don't have experience with setting up sedans...but here's some
setups I tried on my coupe:

D-Spec Settings (first turn cw all the way to firm, then count revolutions ccw)

Spring rates: max 358lbs/in (F) ; max 463lbs/in (R)

1. current "sport/comfy" setting: F3.5 / R4.0
2. touring/comfy setting: F4.0/4.5
3. luxury soft setting: F4.5/5.0


I don't have a 'race' setting because the spring rates are too low for that.

hope this helps some...

 

I wouldn't be so quick to blame the shocks for the ride problem, I would only blame the shocks if you install oem 350Z springs and still have the same result. One question, how much does a single tire/wheel combo weigh on a bathroom scale?

Do to the fact that your X uses a different front suspension then the RWD cars you cannot install any currently avaliable front shock ment for the Z or G (this means coilovers too). Take a look at your oem shocks, and compare, you will understand. Your front sway bar is also totally different btw.

For a fee, you can send your oem front shocks to Koni they will do what is called a "wet kit" install. They will basically gut your oem shock and install Koni internals. Koni has two authorized service center's that can to the work. www.propartsusa.net and www.truechoice.com For the rear, I see no reason why you can't just source oem rear Koni's.

 

Gsedan35- can Koni make those adjustable or do you provide them with a
target numeric damp rate? or do you basically get what they give you?

 

Ken, here's a cut and paste from Koni.


"KONI wet kit conversion"

"KONI can fabricate anything you may need. We can take your existing strut housings and install our internals; we refer to this as a wet kit. We can make a wet kit single adjustable or double adjustable depending on your budget. We can convert the strut body to utilise a coil-over sleeve or we can modify the housing to meet specific needs. KONI can also fabricate shocks or strut inserts. Let us know your needs and we can give you a cost."


Easiest thing to do valving wise, it to simply have them built to copy the specs of the 350Z Koni sports.


KONI North America
1961 International Way • Hebron • KY • 41048
Telephone: (859) 586-4100 • Fax (859) 334-3340
http://www.koni-na.com/contact.html

 

Gsedan35- interesting find. cool info and cool alternative.

Koni Yellow's and most of their economy line are standard one way adjustable
only on the rebound unless you get the bound and rebound adjustable
ones which cost considerably more. I think if you ask for the 2 way adjustables
wetkit from Koni, the price will not be anywhere near $500 of the D-Specs but
would be a great upgrade from the D-Specs.

On these progressive rate springs like the Prokits, it's actually better to have
bound and rebound to firm up simultaneously because on this car the
initial bump is too soft and is the problem area. Tokico's pre-set rebound
rates that change while adjusting the bound rate is actually pretty well
tuned for this car. It firms up quite a bit on bound, but the rebound is still
pretty gentle and keeps the car flat even over huge bumps and dips...but
my choice in spring rates and playing around with the damp rates might
have a factor too.. hehehe

 

Guys:
Thanks for the great info. Bummer that the d-specs will not work for my x. Thanks for pointing that out, GSedan35. The Koni wet kit sounds like my only choice in the strut department, until someone makes a strut for my car.

Hence, I would want to experiment with the springs in the meantime. I haven't weighed my rims/tires, but they definitely are much heavier than the stock setup. Yet, the stock spring + strut handled them very well. The problem only started after I swapped in the Eibach Prokit. KenChan made a good point that the initial compression of these progressive springs is very soft. I'm thinking of using the 350z oem spring because they are linear and firmer. With the Eibach's, medium/large bumps are causing too much compression. My theory is by the time the Eibach firm up, it is already towards the end of its travel. The car would bottom out.

If I use 350z springs only, would the earlier models (2003) work fine? What changed in 2004 to improve the Z's ride? Was it the spring or the strut?

Thanks,
-Ken

 

Use 2003 oem Z springs. The 2004.5 suspension revision changed the shocks to improve ride quality (less compression dampning and more rebound control). But, the specific reason to avoid the 2004+ springs is that they use a much higher rear spring rate that your oem rear shocks won't be able to control correctly.

I hate to say it, I would bet money that neither Koni or Tokico will market a shock for the car.

 

The D-specs are a excellent product and cost less the the Koni's and their ability to double adjust is a asset to those whose needs are met by that system, which is large chunk of the G35 community. Koni's have more compression dampning then oem coupe shocks and oem sedan sport shocks. Their ability to do rebound only tuning is done on purpose, they allow chassis tuning that cannot be accomplished while simaltaniously adjusting compression dampning. Plus the Koni's rebound only ability is a asset when higher spring rates are use. More compression dampning plus more spring rate equals greater harshness. This is why Koni sports are a extreamly popular shocks with autocrossers and road racers. Yes, their are better offerings that cost more, but the Koni's are a good value for those that need what they offer. Looking at the M3 (E46) community, Koni sports plus ground control coilovers are a more popular choice then dedicated coilovers.

 

I know the popularity of Koni's. I have a Cooper-S too, remember?
As you said, the rebound compression adjustability is great to have on
various setups and sport/race applications, but while using lowering
springs on this car (specifically the Prokit/S-Techs) the bound is one
of the major problem areas in the front.

=> Buying only rebound adjustable dampers is a hit or miss....that's
what I am pointing out here. If one has the resources to trial
and error various setups I encourage it, but if not, the D-Specs
is a sound solution to these problems people are having.

I wish there were other manufacturers that do just the
dampers for our cars because Im really soundling like a f-king
Tokico advertisement im doing for free. Koni Yellows,
from what ive read on this forum, has not been able to provide
the user with much satisfaction...this is why I skipped Yellows
and waited for the D-Specs. (also because Tokico OE's the
stock dampers to Nissan.... so why not?)

hummm....D-specs don't fit the X, huh...that is a bummer.
What is different between the X and the RWD sedans/coupes strut/shock
assemblies? Is it a matter of where the ABS sensors/brakeline bracket
go? or more involved?

 

Should I only use the springs from a '03 Z?
or
2004.5+ front spring + rear spring and strut?

I'm searching my350z.com for parts and deciding which direction to go.

Thanks,
-Ken

 

I have no issue with how well the D-specs work in these cars, I have helped install them on two different G35's and got to drive both afterwards. As I've said before about them they have vastly superior to oem valving, with the overwhelming sensation that a lot of R&D time was spend on them. They are one purchase that once expercienced, you will quickly know why you spend money on them, worth every penny. So don't flinch about how much you like them.

But, what I take issue with is this, suggesting that the sport's are a low product in Koni's lineup and that rebound only control is a minus. Koni's have their place when you need how they differ from the Tokico's. When you know the oem specs, the specs of the springs your going to using, their isn't anything hit or miss about rebound tuning that is any more difficult then having the talent to sense when a adjustment is a plus or has gone into the minus. Several Z owners with progressive Eibachs have Koni's, though most use them with linear oem springs or linear aftermarket springs. The Koni's have a very large range that they can adjust covering a wide range of behavior and spring rates. Need to change the spring rates higher still, simply send the shocks away to be revalved, you will be able to rely on trained techs that have been involved in motorsports for years. These are things that you have to have a need for, not many here will. Making the Tokico's a better choice for most.

Here is the thread where we got confirmation about X shocks vs RWD shocks.
https://g35driver.com/forums/showthr...ht=shocks+g35x

Reading the thread again, I wonder if Koni can just do a mod to the lower stem/lower mount to Tokico's?

BTW, while Tein has the ablility to service and rebuild their product at their so cal location, they will refuse to do any shell case or lower fork mods. Won't even sell coilover parts on the side either. So no luck in getting them to mod a off the shelf.

 

If you use the oem 03 Z springs, your oem shocks should be able to dampen the springs. If not, you should into how to make better front shocks happen.

What I worry about if you use 04.5 springs and the revised CD300 rear shock is being over sprung and over dampned. Where's what I mean. I have been running Tein 350Z H-tech's on my sedan with oem sport shocks. While ride comfort had been great and the overall grip level is higher then when I ran a oem 350Z suspension, dampning performance with the oem sport shocks and the 350Z H-tech's is lacking, enough that I do NOT recommend the springs with oem sedan shocks or regular coupe shocks. In advance to installing a new suspension in the front I installed revised 350Z rear shocks. Suddenly my dampning problems went away. But at the limit behavior went down hill. Previously at the limit was very will balanced with just a hint of oversteer. Now the rear would step out much too soon hurting adheasion level's and the fun. And I'm on 375lbs rear springs, not the 2004.5 Z's 427lbs rates. That is what I fear for you, soft front shocks with much stiffer rear springs and stiffer rear shocks.

 

I agree, as you stated below, Koni will need to study the vast majority
of spring rates and lowering available out on the market for the G...cause
it looks like they did a good job making a replacement kit for the
stock dampers on stock springs, (i have not tried them personally so
don't know) but have not yet made any other revisions for better
matching to aftermarket springs out there. Perhaps they can make
a easy lowering spring/yellow combo that matches their damp rates
better.

And, as I have stated earlier, if you're looking to do some trial and
error i encourage it. You can do all the calcuations you want to
get it near the ideal, but there are so many different types of road
conditions, tire/wheel selections, etc. out there that you'll end up
trial and error many times until you find a subjective ideal setting.
That's why automakers do vehicle level tests all the time to find
a subjective ideal setting for most people. I'm a Tier1 supplier, I
know what the engineers go through.

What you're suggesting with the Koni (non-Yellow) path is a higher
level setup for those that are looking for a specific setup...more
of a street/race/professional application. and that's great for those
that are looking for such setup.

I think the subject has slipped some from its original question,
but i think it is important to know that for the most part, the D-specs
which are off-the-shelf can satisfy most people. try it, if it doesn't
make sense, then try the wetkit which I'll consider it as an upgrade
from the D-specs. would I try it? I'd like to, but I'm pretty happy
with my current setup for street. I might consider it for my Cooper-S.