2009 STX changes: Setup discussion for G35
 

With the recent rule changes in STX for 2009 (9" wheels and 265 tires allowed for 2WD vehicles), and me being in the market for a new vehicle, I am interested in purchasing a G35 Sedan, and setting it up for STX. Since the coupe really presents no significant advantage (and more weight to boot), I am more interested in purchasing a sedan...likely an 05-06. Feel free to change my mind on the coupe vs. sedan thing, though that is not the purpose of this thread.

First, I am fairly sure that with the right driver, the G can be at least regionally competitive. Its main problem is all that extra weight, even though it's not a whole lot more than the main competition (05 and older WRX, the newly added RX-8, and the Bimmers).

My main areas of focus, in order, will be:
1. Getting the best/lightest possible wheel/tires. I will likely be using a 17x9 RPF1 (partial to this wheel, as I currently use it on my STS2 MR2), and hope that someone comes out with a 265 tire which will work with it -- otherwise, I'd be stuck with 255. If a 17/265 is not going to be produced, I will regrettably switch my plans to 18/265. I'll probably lean toward whichever competitive tire is lightest, within the 140-200 TW rating.

2. Fitting the best possible suspension I can afford. Coilovers with proper spring rates will be the biggest decision, and I'll hopefully be able to find appropriate adjustable sways for both ends to battle all the lateral weight transition of this beast. My initial thoughts are the Bilstein PSS10, but I'd like to make sure they come with linear springs, and if not....get them. Please offer suggestions here, as I know there are a TON of coilover options for this chassis, and hopefully a few with good damping curves.

3. Reducing as much weight as possible, while not spending tons of cash on negligible reductions in weight (i.e. I probably won't get a $2,000+ BBK that saves 10 pounds total, even if it is unsprung. Not worth it for now.). Prime weight reductions would be exhaust, battery, etc.

Thanks for reading, and I hope I'm not the only one planning on a G in STX! :hello: (supposing I'm not seduced by the WRX...)

+1 for RPF1's. Have you looked into the new Type 2 RPF1's?

Thanks :)
Personally, not a fan of the TypeRC...plus they're heavier.

the rpf1 is a solid choice, the 5zigen fn01 isnt as light but its is probably $400 cheaper when talking about a full set of wheels...if you go 18's i'd go with the rpf1's, they should be considerably lighter in that size.

as for tires, good luck..the stickiest 265 i know of is the federal 595-evo

I'm pretty much set on the RPF1, regardless of what car I end up getting.

Does anyone care to discuss high-end suspension chioces, or overall competitiveness of the G in STX? Anyone with any past experience in this class with a G?

How about Coupe vs. Sedan debate? Can anyone confirm that an 05-06 sedan will be just as (if not more) competent as a coupe?

TIA for any help.
Joe

Buy the coupe, otherwise you'll be left scratching your head about the coupe that showed up with 275's or 285's at all 4 that you could not catch by the end of the day. Sedan's have so little room in the front fenders, see below.

You cannot run a 265 tire on the front of the sedan in a tread width that is wider then the RT-615 255/40-18, even that tire requires very carefull selection of offsets. On Enkei RPM2's with a 45mm offset, they clear both the suspension upright (some sign's of light contact, nothing of concern) and the front fender lip. Install a 10mm spacer and, game's over on the fender lip.

"The best suspension I can get". Straight up, I'm with you 100%, but far too many here and on my350 think they are talking about plan A when they have no idea what they are talking about and give you the hard sell on something that is much further down the list. That being said, make sure you've improved the nut behind the wheel and nailed all the other elements. Like maximizing corner exit traction (VLSD is very weak)

1. Buy NOTHING without first being able to see a dyno plot of the actual product your considering. And if your serious, you'll make sure you see both force vs absolute velocity AND a force vs velocity plot that clearly show's how much or little hysteresis (phase lag or control lag) that the damper has.

1a. Buy nothing that does not have the ability to revalve with as wide a array of valving option's as possible where that work is offered at more then just one spot in the U.S.. Valving option's meaning, piston, shaft and shim stack choices.

http://farnorthracing.com/autocross_secrets6.html

"Buying Shocks"
"Remember this list:"

Bilstein
Penske
Koni
Ohlins
Sachs
Dynamic Suspension
"Not on this list? Almost certainly crap."

Your on the right track with the Pss10 kit. However, the springs the kit comes with aren't with your program. 370lbs linear front, on the soft side. The rear is the bigger problem, progressive wth a really wide rate spread 240-420lbs. Their may also be a issue with the valving, if Bilstein did not alter it vs the Pss9 kit, you will find that higher damper settings become unproductive for performance handling (never roll over and play dead for manufactuer claim's for being "track ready". If you like, I can call Bilstein. I have very specific question's about the damping curves that I can ask for clarity on the subject.

The Pss10 kit can resprung and revalved. That is what I am doing with my Pss9 kit. FatCat Motorsports is finishing working on them right now. fixing the valving issues that prevented higher settings from being productive and allowing them to run with 560/500 rates. Swift makes the 70mm ID 8" tall springs that fit the front dampers and that sillly ebay sleve coilover setup for $179 shipped has perfectly fine rear height adjustors that allow you to use Hypercoil, Eibach ESS or Swift 5" ID 9.5" tall springs.

You can also purchase Bilstein HD shocks for $700, and have Fatcat Motorsports revalve them for use with Nismo T2 linear springs 690/690 (I wouldn't run that much rear spring, easy fix however).

Another choice to consider is used Ohlins coilovers or you can just cut to the chase and buy the used Penske 8100 triple adjustable setup for $3k I discovered today. http://sccaforums.com/forums/thread/336950.aspx

If your willing to accept the issue's their twin tube constuction forces on you, OTS Koni shocks and Truechoice phase III or IV coilovers are another choice. I do not recommend Tc Kline DA shocks, far too much hysteresis at the higher dampning settings. I have Roehrig raw shock dyno's on my Koni's, front Truechoice phase IV shocks and Tc Kline DA's (which I do not own).

You can follow past successfull practice as demonstrated in BSP 350Z's and sellect the most front bar strength you can get. H&R has a 36mm adjustable front bar, rear is adjustable too.

Excellent comments and suggestions, Gsedan35.

There's a few others to add to that list such as Moton, etc..... but likely I'll be staying in the price range of Koni, Bilstein, Ohlins, or maybe one or two others.

One thing is, I will certainly *never* be running against anyone with greater than a 265 tire, as I am building an STX car, where 2wd cars are now limited to 265 tires/9" wheel. So, while it would be good to buy the coupe to be able to run a 265 vs. a 255, I wouldn't be at the optimal rim width (usually 9.5 or 10"), and I'd have the extra weight to boot. Plus, I'd be running an 18" wheel vs. a 17. So, I may actually be better off running a 255 on all 4 corners of a sedan on a 17x9 wheel. Unless I'll still be having trouble fitting these on a sedan. ???

Thankfully someone else pays attention to shock dynos before purchasing something shiny and "JDM." I'm fully aware of what's crap and what's not. Most is crap, if you actually want to take your car to the track and be successful/not have handling properties of a coal cart.

Does Ohlins make a DFV coilover for the G/Z? I haven't been able to find them, though I haven't really looked very hard. These (with different spring rates) were what I was planning on when I was still thinking I could live with the RX-8.

And finally, any speculation/experience as to whether the G will keep up with an RX-8 or WRX (AWD being limited to smaller 245 tires/8" wheels) in an autocross setting? I know there are many other "outside the box" cars to consider for STX, but I'm a fan of the G, and would like to make it happen.

I'm baffled why the SCCA keeps making the max tire size not match with max rim width. Oh well.

I'm not too familiar with AutoX, as my participation has dropped off severely.

The 08+ s2k guys are running 275 front tires...

Does not apply, fortunately.

Here's a *very* abridged list of STX class rules:

-Street tires with > or = 140 TW rating
-at least 4 seats
-Turbo: 2 liters or smaller
-NA: I forget the displacement limit, but it's high
-AWD: Limited to 245 width tires, 8" width wheels
-2WD: Limited to 265 width tires, 9" width wheels
-Weight reductions are very restricted within ST classes...no gutting of interior, etc.
-Any suspension changes, keeping stock pick-up points
-I/H/E are allowed, but at least a high-flow cat must be in place
-Engine tuning is allowed, but is limited; no upping boost in turbo cars.

Very quick explanation, but it keeps the playing field level. There isn't a ST class where every car can play, and I'm not getting into buying R-comps just yet.

I forgot about the Moton's, you do have their shocks and club sport kit avaliable. I had heard that on the Z, they were difficult to dial in, the shocks that is. I don't have any feed back on the club sport kit. I do know of at least on person running them. Curious, you mention "one or two others", what are you thinking?

I should have read more carefully about the max tire width being 265, sorry.

I can find the Enkei wheel your talking about in 9" width on the Enkei web site, though I do see 9.5". Are we talking about the same specs as shown on their site?
http://www.enkei.com/RacingSeriesSpecs/RPF1.html

Ohlins currently offers the DFV and some resellers may still have the PCV version still on the hand as well. http://www.z1auto.com/prodmore.asp?m...ng&prodid=2155
They are rebound adjustable. What I do not know is how much of the Ohlins parts catalog can be applied to them besides shims and such. A call to Ohlins USA should clear that up, they are extreamly nice and their web site show's who is authorized to revalve/repair.

Only Koni's I'd recommend are the already developed 2812LB monotubes and even then I would spend that money with someone else.

If you find yourself driven by costs and you end up considering something like OTS Koni yellows, I will have the following items for sale soon. Of course I'll still say, I recommend other choices

OTS Koni yellows
Custom 6061 front spring seats
Tein tapered linear front springs 448lbs
350Z oem revised rear springs 427lbs
oem cut down and shaved rear spring seats
$550

Truechoice Phase IV DA front shocks
Oem front upper shock mounts modified for Koni coilover top hats
Koni 65mm upper spring seats (top hats)
Koni coilover sleves
generic 560lbs springs AND Hypercoil 650lbs springs (recommend revalving for the 650lbs springs, compression is fine, up rebound)
TomsMotorsport adjustable rear spring seats
Eibach ESS 5" ID 9.5" springs 450lbs
Rear shocks not included, will need to buy new Truechoice Phase IV rears shocks).
$650
^Add in the $950 for the new rear shocks and you will will be at $1600 total for a setup that sells for $3k new.

If the Z has it's hands full with the RX-8 in BS and BSP, the sedan isn't going to fair better, not with greater weight and the added wheelbase length that won't favor tighter courses. I can't comment about the WRX. If the rules allow you to pull the oem VLSD on the G, I'd do that in a hurry, I favor the Cusco RS myself.

Yup, I think that's the 17x9 RPF1 I'm looking at, though they often times make runs of other offsets and lug patterns that are not advertised on their website.

The others aside from Motons which are a "maybe" are things I probably won't be considering myself, but that others have had luck with. I don't know if they make anything for Nissan, but the Miata guys have a lot of good things to say about AFCO and JIC...JIC seems sketchy to me, but I'll leave that alone. The same could be said for Cusco dampers IMO.

It seems like your Truechoice setup *should* be quite good....I'm curious why you scrapped all that in favor of the PSS9s? Is the Bilstein damping really *that* much better? (I have both Bilstein Sports and Koni yellows on my current cars, but they can't really be compared to one another as one is a DD, and the other is my race car)
Another item I'd question is, with all that work, why didn't you use adjustable pillowball mounts for the Koni/Truechoice setup?

Again, I haven't really made up my mind as to whether the G will be my final choice. Good comparisons with the Z not keeping up with the RX-8. That makes it a lot tougher to decide on the G for STX.

And to think, all this is because I just moved to TX, and my race car doesn't have AC. Maybe I should just buy a pickup to tow the d4mn thing... :dunno:

hi there,

First thing first, where do you find a copy of SCCA solo 2009 rulebook? I can't find it on their official website. Last year they limited STX class to have max. 8" width wheel and 245 tires.

About 255 width vs. 265 width, I wouldn't stress about that extra 10mm, you won't see a huge performance offset, not to mention there are more tire choice in 255 tires size.
For touring class, Bridgestone RE-01R or Dunlop Direzza Z1 star spec is the way to go. I used Azenis RT615 and Kumho MX before, but in term of maximum grip and feedback, MX was okay, RT-615 was great, but it can't handle any heat at all, it overheat too easily.
Near the end of the 2008 season, I switched to Z1 star spec. At the same time, I co-drived a few cars with RE01R. So for feedback, grip level, and temperature thereshold, RE01R or the Z1 star spec is the best street tire you can buy with treadwear rating 140 or higher. For the money, Dunlop Z1 star spec hands down. :biggthumpup:

It looks like you already have put some thought into this, but before I disagree with your platform choice, let me share with something that I've observed.

I won STX class in my region in 2008 by using a 96 240sx (S14), those 3 series bimmer and WRX had put up some good fight from time to time. I've also took my G35 coupe to compete in F-stock class for 2 events. From what I have experienced, the board torque curve of the VQ35 is a great advantage for driving out of those really tight gate and hairpin; but the car weight so damn much, its difficult to maintain momentum and smooth transition. So in those slalom heavy courses, its hard to make fast time with this somewhat long wheel base and heavy G35. With the penalty of carrying all these weight, I doubt its going to be competitive in STX class against those WRX and 3 series bimmer. I can't stress how important weight is in autoX, tossing around this such a "big" car can really hurt you. Even with lightweight battery, wheels, and exhaust (there aren't much left you can do legally to cut weight in touring class), the car will still weight over 3,300lbs. Another reason why I did well with my 2,700lbs S14 with deficit of grip and power.

But if you want to stick with the G35 in STX class, I would recommend concentrate on the best alignment setup and tires. I wouldn't stress too much about suspension because good tires and good driver and make up for it. I recommend RE01R if you have money, if budget is tight, Z1 star spec is just as good.
If you have time and insist to spend more money, do some calculation to find out the proper spring rate to suit your wheel rate in autoX speed, talk with representative from Koni and get them to valve their 86 series shocks for you per your spring rate, put on a decent size of front anti-roll bar and that's it. (I prefer no rear bar btw).

Personally, I think the G35 is more suitable in F-stock class, to run against those Mustang. In stock class, you can use R compound tires (which gives you a HUGE advantage), you can still use lightweight catback exhaust, and substitute the front anti-roll bar. There's plenty of "mod" to let you go really fast, and make you competitive against those Mustang. It depends on how competitive you want to be, and how bad you want to win. But I think there's better chance in F-stock than STX class with a G35.
Oh yeah, if you want to score point in your region with PAX scale, there's virtually no difference in PAX factor between STX class and F-stock Class. So I would definitely pick F-stock class so I can run R-compound tires and move my name up to the top in term of RAW time and PAX time.

If you want to enjoy the modification "freedom" in STX class, I would seriously pick another platform. Believe it or not, FWD Civic Si is actually very easy to drive, lightweight, and they do really well in both STS and STX class. I raced a WRX in STX class before, not my cup of tea. 325i was okay, but not light enough.

Just some food for thought :) good luck

It's one thing to spend $600-$800 on OTS Koni's, quite another to add to that investment with anyone's revalving service, be it Koni, ProPartsUsa, PerformanceShock or Truechoice. You are still attempting to make a purse out of a sow's ear. As you push the core twin tube design to do higher accomplishments you end up with hysteresis levels that also go higher and higher. They won't tell you about this, they won't show you plots that reveal it's presense. It deminishes performance vs other setup choices that have little to no hysteresis. I know full well that lot's of people run the them and other Koni twintube variants and can talk all day about finishing here or their. It's the same logic that has some running other inferior dampers that also don't mearue up, yet they "feel great". And let's draw a line of distinction that we are NOT talking about a twin tubes from JRZ or Ohins. I have seen at least one AFCO plot that did show hysteresis. So,.......I think a majority of people (me included) are and have been happy to a point with Konis on stock springs, they are a good formula that works well for a variety of situations and I give them credit for having fitments for so many vehicle, plus very good reliability. I used Sports for years and felt they were fine until I started feeling a vagueness when using stiffer springs ( 560, 448, 427 375). I also disliked some characteristics of the ride that I can now attribute to hysteresis. I also got curious about the Penskes and Koni monotubes that were so popular among the fastest racers. I started learning about the differences between twin-tubes and monotubes and I decided to try out Bilsteins again (had revalved Bilsteins years ago) for myself. With the improved control, I have not looked back.


The average shock dyno only shows the 'average' force vs. velocity, not the true curve of how the force changes for the entire stroke. So you do not see where twin tubes always have more hysteresis because the pressure build asymmetrically, causing pressure imbalances. Imbalanced internal pressure leads to a lag or delay in how the shock responds to the road, which is the definition of hysteresis. Not good for performance, predictability, or grip. That grip comes from controlling the tire/ground wheel interface with the lowest variation in tire load. Twin-tubes can be made more comfortable than monotubes because (ironically) they cannot control the car over small undulations. Real comfort comes from managing the suspension from start to finish, not allowing the damper to be 'out of control' which again, is what hysteresis is. Except in situations where you want blow-off to occur. Yes, bump needs to blow-off before rebound. With a monotube ability to pass ample amounts of fluid in both bump and rebound, you will ALWAYS achieve better overall ride quality than a twin tube.

Front Koni OTS yellow Max rebound adjustment is 2 1/4 turns, plot I have was run at 5ips or 3 ips vs the 10ips.
http://pics.montypics.com/gcoupe35/2...e_velocity.jpg

http://pics.montypics.com/gcoupe35/2...s_velocity.jpg

Below show's exactly what I'm talking about, notice the blue lines, notice how much variation in force their is between them and where it happens. Having a damper design that have little to no hysteresis that also hits the elements you need on the plot will be the faster car.

http://pics.montypics.com/gcoupe35/2...hysteresis.jpg


Max rebound setting is 11 sweeps, I either don't have a graph at the max setting or it was done at 5ips or 3ips. I will add that I did not find settings above 6 sweeps productive
http://pics.montypics.com/gcoupe35/2...e_velocity.jpg

Hysteresis isn't as bad as the fronts, however, dial in more rebound control and it will become worse.
http://pics.montypics.com/gcoupe35/2...esis_shown.jpg

To add,........

Front motion rate is .688
Rear motion rate is .649 (at oem location)

HOWEVER, do keep in mind that bushing compliance (and bushing function that isn't compliance related, as in all upper camber arms that aren't on sperical bearings instance bind in place as a normal function) can effect wheelrate, doing a bounce frequency test where you get a Hertz frequency measurment on known spring rates is a better data source for valving then motion rates alone.

What spring rates to run ultimately comes down the math being right AND proving the math with actualy testing. The following give's some insight to a winning Grand-Am teams testing on the 350Z in terms of spring rates.

The following quotes comes from a interview of the owner of Unitech Racing Jackson Stewart, the crew chief for the 350Z Grand-Am team Jeff Wisener and the owner of Perfomance Nissan, Michael Cronin.

SZM: "I noticed a trend that many Z owners are putting coil-over suspension systems on their cars, but you mentioned today on the track that many people are putting too stiff a suspensin and actually making the car handle less effectively. Is that true and can you comment on that again, please?"

Stewart: "Yes, it is absolutely true. Most of the aftermarket suspensions sold for the car are way too stiff. More often then not, for actual track performance, a lot of upgrades are hurting the performance of the car."

Cronin: "The common perception is you don't want a car to sway in turns, squat during acceleration, or dive during bracking, but those are things you need to have the car do to handle correctly."

SMZ: When setting up your race cars, did you use or try any of the common aftermarket suspension kits that are avaliable?"

Stewart: We looked at then in a sense that we wanted to know what was out there, but we also had gone through a range of springs on the car and if we went siffer, we lost performace. We have a range of a few poinds we use in the rear to make it oversteer or understeer. So if we see a spring someone is running on the street that is 50 percent stiffer, they are losing overall performance." {His use of the 50% number is a somewhat ironic number to toss out given that 314lbs upped 50% is 471lbs and yet they went with 525lbs or +67% in the front. Unitech did the R&D for the Truechoice 350Z coilover system and that setup uses 525/425 spring rates}.

Same interview makes mention of the following,....
Future parts for sale:
Moton Club Sport suspension package

To comment on the above, they switched to a Koni 2822 4-way monotube setup