Ape Factory

iTrader: (3)

This is how my car sits now with my current height level on Aragosta suspension (Type S). I'm lowered less than an inch front and rear but it WAS necessary to install front upper suspension arms and rear camber arms. Know that going in. I'm also in the process of fixing all the broken photo links due to Photobucket deciding to sh*t on all their users and the entire internet in general. So if there's a broken photo link, I'll repair it eventually. It's been very time consuming so be patient! If you're looking for a particular image, just PM me.



This is a bit (you think?) long-winded but I need to think this through.

I’m in the hunt for a set of aftermarket shocks/springs for my IPL and it’s honestly been a bit frustrating and basically an exercise in managing compromise at my price point.* I’m not doing this to lower the vehicle, only to improve overall performance. I tend to like a bit of aggressiveness but not knock your fillings loose or skittish.

I do like the stock suspension on some levels but feel I could use firmer springs and an adjustable shock to dial things in a bit more to my overall liking. The faster you go, the heavier the car feels. There’s virtually no jounce which is good but it'll understeer something fierce on aggressive turn-in and wallows too much in high speed sweepers.

Most likely, after installation and corner weighting, it’ll lower the car ever so slightly (hoping to keep it about an inch in front) and I’ll be leaving the rest of the suspension alone apart from traction arms with solid bushings.* Most of the time the car hides it’s weight well but this isn’t always the case and overall the handling just isn’t intuitive like a few vehicles I’ve had in the past.

The car probably won’t see a track day for some time if at all. I spent quite a bit of time and money in the past dialing in a single turbo FD RX7 complete with Aragosta suspension system, AP big brakes, Volks, stand alone ECU, the whole nine yards.* It gets expensive really quickly and I’m keeping the G as a daily driver.* I have the mod bug however and well, we know exactly how that goes. My goal is to increase mechanical grip overall, lessen understeer and keep the car from becoming tail happy, traction challenged at the same time (I already have the traction issue).

After doing a lot of research, I’d like to stick to a true coil over up front and the separate shock/spring OEM-style setup in the rear.* There just seems to be too many compromises, one being structural, using a full true coil-over setup on all four wheels.* Conversely, one has to adjust both the spring seat and shock bottom on the rear to adjust height on the OEM-style setup and there’s more unsprung weight. Definitely not as tidy and it limits my options.

I’m fine with a one, two or even a three way setup.* I have enough experience dialing in suspension on cars and bikes.* My only issue is there doesn’t appear to be anyone within an hour of me who has a proper scale setup to corner weight the car.* I know a three way setup is total overkill for the street but I enjoy the process and I’m pretty meticulous with notes while I’m dialing things in and I have “routes” to test things out.

I’m not interested in lowering springs as it brings the stock IPL shocks out of their optimal range and will ultimately lead to premature wear. It also doesn’t solve some of the low speed compression and rebound issues the stock setup has.

Honestly, after looking at all the available shock options I could find for the G37, they all come with compromises. *

It seems that most of the under $2K setups, especially the recent upstarts, are all using the same Taiwan or Korean shock manufacturer with their own anodizing and a few small changes to separate them from the others. *Yes, some of them “build” the shocks here but all the parts are sourced from those two companies. Doesn’t mean it’s bad stuff but it is built to a price point.

To do it properly, it looks like I’ll need to spend just shy of $3K and even then, my options are limited.

I’ll start off by saying the ever-popular KW v3’s are very close to what I’d be looking for IF they came with upper mounts and if one didn’t have to pull the entire unit to adjust compression on the rear shock. They’re also progressive springs and are barrel type both front and rear (more weight). I’m not sure how much better they are ultimately, than the stock IPL setup in terms of feel and damping rates.

I’ve considered the Bilsteins as well but can’t find any real data on their spring rate or damping curve. It also doesn’t come with upper mounts. I want to keep my low mileage shock/spring setup intact and boxed up in the garage if there’s an issue with the aftermarket stuff.

Initially I was going to go Aragosta and knew I’d be spending pretty close to $3K which is my artificial upper limit. I could spend more but there’s really no point on a car like this. Plus if I needed a rebuild, it’s Japan and back or nothing at all. Gets costly from a monetary and time standpoint.

I’ve been looking hard at the following:
Fortune 510 series
Powertrix Ultra-light
Stance Pro Comp 2’s
Tein Mono Sports or Flex Z

I’d kind of convinced myself to go with a Tein product after nixing the Aragostas as I’ve used them before. Problem is, it’s impossible to order Tein shocks with spring rates other than what they’ve deemed acceptable for the U.S. market and already come with the kit. Some of their rates, especially the front to rear ratio, are just whack for lack of a better term or are really firm. The Monosports fall into the latter category. So you’re spending $1800+ on a single adjustable steel shock plus another $400 for springs. And then there’s the cost of the EDFC, one of the good reasons to go with them IMO. All told, that’s putting me in the double adjustable area for Stance but I digress…

To be continued...

Ape Factory

iTrader: (3)

Continued...said my whole post was 10,000 characters too long, LOL. Hey I type 60 words a minute. Anyway...

Tein pretty much admitted the Mono Sports are mostly for the track and not a good street shock. Which leaves me with the Flex Z’s.

They’re probably pretty much equal to the IPL’s with the ability to adjust rebound and they have a 2K bump in spring rate f/r. Seems to have the right rates too at 12K front, 10K rear. Twin tube so has lots of suspension stroke but ultimately not as much “performance” as a mono tube. I believe these keep the OEM rear spring location but it’s been hard to locate a photo of the actual setup. And these are inexpensive. I believe one could forego the EDFC and purchase some rear adjustment extenders since they probably use a small allen screw to secure to the top of the coil over adjustment ****. If I did go EDFC, I’d go for the active as the motors are controlled wirelessly. I’d still have to find a place to mount the unit however and it’s one more thing to install and troubleshoot.

Moving on to Fortune, they don’t make a 510 series for the G37. They can build them however and use their ultra digressive piston in the process. The 500 series adjusts rebound only whereas the 510’s adjust rebound and compression at the same time. This is why I wouldn’t use the 500 series. The 510’s are a bit over $2K with Swift springs and the OEM rear spring location. Their double adjustables are big money with no current option for the 370/G37.

Powertrix, or so I’ve heard, is essentially a Stance shock that they set up to their needs/specs. I believe it’s a 500 series but I could be mistaken. They get decent reviews but I”m not sure they’re using the latest digressive piston technology or a standard linear setup. After my initial conversation with them, I can get the ultra-lights with the supersport type damping and softer spring rates with valving to match. It’s single-adjustable only (comp and rebound at once) and retains the OEM rear spring location. For a maxed out set of UL’s with Swift springs, I’m at about $2K with a few add-ons like rear adjustment extenders. The UL shock is all-aluminum and a different design from the SS and Race which use the same damper unit and different valving. He’d also use the delrin top mounts on the UL’s for me instead of pillow ball. They’re a good value, it seems, with the stock springs but the extras add up quickly pushing it on the edge of the price/performance envelope compared to the competition.

Last up there’s Stance. I wasn’t too hip on their recommended spring rates for the G37 (13K front/8k rear) and it looked like they were true-type on all four shocks. Well, they do indeed have an OEM spring location option (see Powertrix) and I confirmed this during a phone conversation. What I am currently hearing is they can’t source a rear barrel-type spring from Swift in an 11K rear spring rate. I’d be going with the Pro Comp 2’s, valved for 12k front, 11K rear but now with mismatched (brand) springs. The shocks would not have pillow ball upper mounts (a good thing for me). I can also get an aluminum shock body saving weight for about $400 more. But I’m looking at about $2700+ for the whole shebang, $2300 and change for the steel-bodied shocks with Swift springs up front and Stance springs in the rear. And they’re true double adjustable with separate compression and rebound damping. They have Comp 3’s too which would be way fun but I’m over $3K with those. They’re also using quality synthetic damper fluid (Amsoil I believe).

I could go with a higher spring rate as the rebound damping is really what makes a setup feel “harsh”. The spring rate just stores energy for wheel movement and determines the frequency response of the wheel over imperfections and allows the wheel to move more quickly back to the road’s surface. The shock controls the rest and if it’s well-matched to the spring rate, things, theoretically, should be good. Ultimately it’s not quite that simple but this is already too long

The stock IPL spring rate is essentially 10K front, 8K rear (rounded off, it’s more like 9.8f/8.02r). The IPL has about a 12” longer wheelbase and is about 400 pounds heavier than a 370Z. I think most of these shock companies have experimented with 370’s and sort of offer the same rate for the G given the parts all interchange.

So where it sits now, I have an email into Powertrix to see if they indeed use a Swift spring in the rear (they have a 13K/11K option listed) or if it’s just up front. I’m not sure everyone at Stance really has a clue as to what they offer as a forum vendor received different information from what I was told over the phone. I’ll most likely call or write and see if they can do a 10K Swift in the rear. Maybe Hyperco has one, who knows. Just more research and sourcing I’d have to do after the fact.

My ultimate setup with cost as a consideration would be double adjustable aluminum montotube shocks with digressive piston technology, 12K front, 10.5K rear (adjusting rear spring preload), OEM rear spring location, rear extended adjusters with Swift or Hyperco springs all around.

The other companies I see often like K-sport, Megan, D2, etc…all seem to be sourced from Taiwan but generally, from a performance and valving standpoint, they seem to be more generic and less performance oriented if that makes sense.

At this point I about ready to “settle” for the Flex Z’s, save some dollars and buy a set of Wedsports I’ve been eyeing for larger rubber up front and in the rear. I contemplated putting a set of rear IPL rims on the front but the cost and difficulty in hunting them down makes it just not worth it.

Anyway, that’s my first world dilemma. Any suggestions appreciated.

PNW_IPL

iTrader: (5)

Subd.
Great read. Sounds like you have a plethora of knowledge.

slartibartfast

iTrader: (7)

Finally, someone who's been asking the questions I would should I decide to go with coil-overs.

Have you run across any wheel frequency data for Gs or Zs?

Are you excluding "true" type rear coil-overs? If you consider them, they'd have "whack" front:rear ratios since the motion ratio will be significantly different, i.e. rear motion ratio reduces from something like 2:1 towards 1.5:1 or less, thus lower spring rate.

Keep us apprised of your findings, please!

Ape Factory

iTrader: (3)

I've not run across any frequency actually...there seems to be a lot of Z guys who are hard core track junkies/racers but again, given how different the actual stats are on each chassis, I don't think it's really that applicable to the G. Plus they're mostly full race or a seriously hard core setup that's barely street able. Neither of which I want. But...it'd be interesting to read as the suspension layout is the same and obviously the parts are interchangeable. So there's some knowledge to be gleaned from their discussions. Most of what I see is "yeah the coil overs are great and I was able to really slam my ride" type stuff or it's all out Ohlins/Moton/JRZ stuff and nothing in between.

There's one really interesting thread where two engineers discuss the effect of moving the springs inboard and onto the coil over vs. the OEM location and while it certainly wasn't definitive, it did give me pause on going with a full coil over setup. There is some discussion actually about frequency, moments and the effects on the linearity of a spring or lack thereof due to it's location. I'll see if I can find the thread again and post a link.

One of the Tein setups I saw was a 14f/14r spring setup with the spring in the OEM location (Tein Mono Flex). I used to run 12f/12R spring rates on my FD but it was also 50/50 weight distribution and the car weighed 2550 pounds without me in it and half a tank of gas. The car was dead neutral in steady state cornering until you hit the gas and the turbo spooled up. Then, not so much.

And as you pointed out, the rates could be on the strange-looking side because the rears are inboard. It's often very hard to tell if they're full coil overs or inboard. Typically, if they're softer, in the 8K range, I figure they're inboard coil overs. But it's not always the case and if you look across all the manufacturers, there's not much of a theme in terms of spring rate or between front and rear ratio. Just take a look at all the shocks from say HKS, RS-R, Cusco, Tein, or any other JDM manufacturer.

The more I think about it, the more I believe our cars really really need more front tire (and lighter wheels would be a huge plus too). I think that combined with a matched spring/damper rate that's a bump or two above the IPL's rates, proper front/rear ratio more towards neutral handling, corner weighted, you'd have a very capable, streetable car. One can bring up alignment specs and sure, you could go with a very performance-oriented alignment and chew through tires and it'd be all over the road following every imperfection.

The more I write, the more I'm leaning towards the Teins. They can actually send you custom valved shocks and I think they're selling for $100 each, manufactured in Yokohama. Not a bad deal and it's not too far removed from the IPL's suspension. One thing I've realized after modding various cars and bikes over decades is OEM engineering is usually pretty good and very hard to improve on in a street scenario.

And I do want to give a big thanks to Charles at B2 Auto. I emailed a few vendors on this forum with questions and he's been the ONLY one to respond, each and every time. I have zero affiliation with them, just a past customer and he happens to be one of the vendors who's a Tein and Stance dealer.

blnewt

iTrader: (13)

Very nice write up and really nice to hear your thought process through all of this. The fact that you've already done all this (and much more) to your previous vehicle will provide a valuable resource for anyone contemplating a similar purchase.

Have you considered a Koni shock setup w/ springs in your desired spring rates? Also the HKS sets get good reviews although getting that minimal 1" drop may be a problem.

Ape Factory

iTrader: (3)

I actually haven't looked at the Koni's yet but should probably do so. The one caveat they have is you can't corner weight the car without going with a true-choice like adapter to raise or lower ride height. Once you do that, you're affecting spring preload and ultimately the spring rate. All of the options I'm looking at have a threaded shock body with the height adjustment performed via the bottom bracket which is separate from the spring preload collar up top.

And that just set off a lightbulb in my head...if you go with the OEM type in the back, any adjustment to height is affecting it's spring rate. Unless I go with a true type. Doh! Also a true type has a far more linear rate it appears than the OEM location.

blnewt

iTrader: (13)

There are quite a few of the Z guys that bolstered up the rear upper shock mount to help w/ the concentrated load in that area (I'm sure you've see a few of those solutions since it appears you've done a lot of homework). That would make going w/ a true coilover rear setup the better choice (seemingly). And you could then remove the OEM lower control arm and go w/ toe & camber arms.

It seems hard to find any coilover that will allow as mild a drop as you're wanting though, especially in the back, maybe a custom spring length could get you there assuming you could still maintain full shock travel and not void any warranty.

There was a European H&R Koni combo listed here, but AFAIK it's not available here
Koni Sport Suspension Kit for Infiniti - larkspeed.com

JM Auto Racing

iTrader: (8)

I unfortunately can not write 60 words a minute so I would love to help you out and answer some questions. Can you call us at 855-998-8726. ASk for Joe.

slartibartfast

iTrader: (7)

To clarify spring location and motion ratio: moving the spring out to the shock reduces the lever arm of the rear control arm on the spring, thus a softer spring is necessary for a given wheel frequency. If you'll check out the RWD sedan coil-over sticky, you'll note at least one mfr uses 12k/6k instead of the typical 12k/10k or thereabouts; that tells me it's probably a true coil-over. The inboard stock spring location requires a higher spring rate to keep a specific wheel rate/frequency.

Spring preload does NOT affect spring rate. Spring rate is a constant that is determined by wire diameter, free coils counted with the spring uninstalled (essentially the length of the wire) and the modulus of elasticity, which is a constant.

Preload DOES effect ride height and comfort. The motorcycle guys have been arguing this for nearly a century.

I modified my NC Miata quite a bit and eventually put Ohlins on it. There's a guy named Shaikh who runs FatCat Motorsports who published a spreadsheet with all the parameters required to calculate wheel rates and frequencies using whatever spring rates and sway bar rates you wanted. The Miata guys are quite knowledgeable about suspensions and I learned a lot. Now that I'm retired, I might just measure up the G's suspension so I can emulate the FatCat spreadsheet. He made his business rehabbing and revalving Bilsteins as long as they were crimped closed. He didn't mess with the sealed shocks, though. Makes me want to re-evaluate the PSS-16.

Some 411 -- Wheel frequency should be one's primary measure of suspension capability. Luxobarges tend to run about 1 Hertz. Most super cars are at 2 Hz. Ground-up race cars approach 3 Hz. Frequency measure how quickly the suspension absorbs a disturbance and returns to steady-state. For the uninitiated, Hz is cycles per second. The higher the frequency, the more quickly steady is re-attained. As one might expect, higher frequency is stiffer. And less comfortable. I'm going to guess the G37S has a frequency of approximately 1.3 Hz. Naturally, as frequency goes up, so should shock damping to control the faster motions.

As for more front tire, I think that would require a softer rear sway bar. With VDS turned off, the G Sport is very tail-happy with the stock bars and tire width. So much so that I leave VDS turned on all the time.

This is a fun thread. I'm really glad you started it.

blnewt

iTrader: (13)

Agree 100% and glad to hear your thorough thought-provoking replies

VenomGT9

iTrader: (4)

OP...

Love this thread. Please make more on each aspect individually, need a good read.

Ape Factory

iTrader: (3)

I actually leave my VDS on all the time as well as I've noticed a distinct lack of rear traction coming out of corners. I took a particular corner quite hard and threw it in there and was met by alarming understeer but it pulled through with a bit of throttle until I was almost straight, nailed the throttle and tried to keep it out of VDS range and the tires just spun and spun. Zero wheel hop and eventually the rears gripped. I think some of this can be fixed with an alignment and better tires.

The particular thread I read regarding the spring location specifically debated wheel frequency quite a bit between the two setups. For the life of me, I can't find the thread but it involved one poster using computer modeling (somewhat unsuccessfully) and a number of seemingly very knowledgeable people stepped in with counterpoints. Was a great discussion and worth reading the entire thread before making any decision on which way is best. If I remember correctly, the actual rate of a spring at the wheel in terms of frequency changes depending on where the spring is in position to the wheel. So a true coil over retains it's higher rate at the wheel vs. an outboard spring which looses a good deal of of its stated rate when measured at the wheel. I think I'm explaining that correctly!

And you're right about preload on a linear spring. Brain fart. I used to have an NB as well although the wife drove that so there was very little I did to it other than headers. All the money went towars the FD, the Evo, the Aprilia and the Ducati I was always having to swap springs on the bikes due to most being sprung for 170 pound guys and I was at 225. I used to battle the bikes until I had proper spring rates front and rear and could get proper sag without maxing out the preload.

blnewt, I really don't want to modify the shock towers. I believe most of those guys have literally cut the top off and rewelded in a stronger piece. If I were going all out, yeah I'd maybe consider that. Now there are some guys who've run rear coil overs for years on the track and haven't had an issue. I haven't found a thread about any failures but haven't really looked for them either.

Joe@ JM, very much appreciate the offer. Assuming you're open on Monday. Will give you a buzz!

slartibartfast

iTrader: (7)

Shaikh/Fat Cat has quite a few YouTube videos that are very educational. For most users of the board, their eyes will glaze over after five minutes of the first video, but anyone who really wants to understand dampers should take a look. He also talks about lowering springs and sway ... err, stabilizer bars, too.

I noticed during one of his videos that he has dynoed the Bilstein PSS for the G35. I'd like see that.

Motion ratio is what they were discussing on the Z board. For FWD, a one inch deflection of the wheel equals almost one inch deflection of the spring since the spring seat is at the wheel hub. The motion ratio is 1:1, for discussion purposes.

For our RWD Gs, the spring seat is much closer to the control arm pivot, which provides a lever moment, or mechanical advantage to the wheel. That one inch wheel deflection equals only about one-half inch deflection of the spring, thus the motion ratio is 1:0.5, or 2:1 to use whole numbers. Since the spring compresses only half the distance as the wheel, the spring rate has to be stiffer to control the wheel rate than it would be if the spring was at the hub.

That's a crucial measurement when trying to determine wheel frequency.

Going from the OEM tires to Potenza S-04 Pole Positions did much for keeping the VDS nanny quiet. Cutting the OE toe-in by half on both ends helped the car turn, as did camber arms. I had my tech set them at -2º. Suspension is otherwise stock.

My Bandit got a new suspension, too. The Gold Tech front became so supple yet well-controlled, the difference was astounding. The rear, I made the mistake of using too stiff a spring and it was a painful ride; I had to stand on the pegs going over railroad tracks or suffer butt hurt. At least the Progressive brand shock stopped the wallowing.

Ape Factory

iTrader: (3)

I'll do a search for his stuff, thanks for the heads up!