Silverton

What custom spring rate and drop for a "club sport" daily driver (that is run a few times a year open track) would you recommend? I'm looking at either TC Kline Koni DAs or the Truechoice Phase 3 Koni DA coil-overs. Sway bars are 350 Evo. As a daily driver I want no more than 0.25" drop F/R (about like the Tein H-Techs). The springs in the Truechoice / Unitech Review thread are 500lbs / 425 lbs F/R, but these are for a much more track oriented setup. Any suggestions are greatly appreciated.

Gsedan35

iTrader: (10)

As far as TC Kline Koni DA's or the Truechoice Unitech coilovers,...well. The Truechoice setup will allow you a measure of ride height selection and the ability to corner weight. But, we have rather well known very serious concern's reliability with at least one owner of that system.

Truechoice
Pro's:
Shortened shock bodies and piston shaft lengths
Coilover's with the abilty to adjust ride height and corner weight
Valving determined by track testing by the Unitech race team

Truechoice
Con's:
The reliability question


TC Kline
Pro's
The ability to adjust compression damping and rebound damping seperately from one another vs adjusting both together.
The ability to cover a wide range of spring rates
Because they are custom made by Koni for TC Kline, you can add on Koni coilover part's on the front shocks giving you ride height adjustablity and the ability to corner weight.
Valving ranges set by a company with a very active race team.

TC Kline
Con's
Same shock body length and piston shaft length as off the shelf Koni SA's*
Having to dial in the compression and rebound settings to be ideal.
http://www.amfmotorsports.com/prod/koni.1.1.htm

*Why does this matter? With my custom Koni coilover conversion, I noticed that at a oem Z ride height that I did have much bump travel on the 448lbs springs I was using, about 1.5" and this was with shortened bump stops. I realize that with my sedan I have greater corner weight's, but we're only talking about about a 200lbs whole car differance. Makes me wonder how a Z Koni/eibach spring combo get's by with a 1" lowering. That being said, I was happy with the 448lbs front rate. I tried rear rates in the following order, keep in mind that I was running revised Z shocks in the rear vs rear Koni's. 375lbs, then 427lbs and finally 342lbs. The suspension is off the car now because I pulled the front's off and sent them back to Koni, the left front shock had started to spray oil out around the top rebound adjustment blade. Koni sent me two brand new shocks, so at least I know they did not find any proof that I had bottomed out the shock's internally.

I did get a responce back from proparts usa concerning shortning my front Koni SA's 1" and revalving them, I thought $180 per shock was pretty good considering that revavling alone run's $115.

Silverton

Right now my preference is for the Truechoice system. Reading daveh's last post in the Truechoice / Unitech Review thread seems to indicate his problems were with Unitech and their rear spring perch. The serivce from Truechoice seemed excellent. Note that John Ritt's rear perch is not Unitech but JIC, and he's had no problems.

For either system, however, my question is what springs to run for a club racer. Truechoice tells me that I could use a 450lb front spring with a 0.25" drop (close to the H-techs in drop). But what rear spring? I feel that the Unitech 500/450 lb F/R springs may be way too much for a daily driver.

From reading posts in this forum on lowering, I don't think I want to exceed a 0.5" drop for a daily driver.

daveh

iTrader: (9)

Just a quick correction. There is no problem with the rear spring perch. All my issues have been tied to bad shocks and noisy upper monoball mounts. At one point, I thought the problem my have lied in the perch but I was mistaken. I think the standard springs (500 and 425) on the truechoice set are ideal for a street driven track car. I wouldn't go any lower due to the limited suspension travel of the Z, you'll run out of travel. I may some day go higher actually.
Skip the upper mounts and re-use the stock rubber bits and you should have a 'decent' street ride. One thing to note is that the street ride is a little choppy on slow speed bumpy roads. This suspension really shines on the (high speed) track and is just average on the street.
I know very little about the valving of TC's shocks, but the construction seems to be comparable to unitech's which allows for a wide array of spring choices due to the high level of adjustablity. Personally, if I were to go with TC's shocks, I would get the T2 springs since that the platform they were developed on. This wouldn't meet your daily driver needs although it probably wouldn't be as bad as you think.

daveh

iTrader: (9)

I belive that JRZ makes a DA setup for our cars now. ALong in Seattle has them on his race car and raves about them. Looks like you're local to him..

Silverton

Is it possbile to get a 0.25-0.5" drop using the Unitech 500/425 lb springs? If not, are there other choices? Phil, at Truechoice, tells me that 450lb or 500lb springs are available for the front and I could adjust the ride height to get to 0.25" drop. But he has no alternatives to offer at the rear.

daveh

iTrader: (9)

I don't see why not. I'm currently at a .75" drop. I think lowering the spring rates would be cause a lot of damage to your undercarriage when you bottom out the car.. Please note that if you have a good set of shocks (like the truechoices) the dampening smooths out the ride of a higher spring rate.
Can I ask what tires you're going to be tracking with? That will also make a differnce in springs and dampening choices.

palepony

iTrader: (8)

Gsedan - "I tried rear rates in the following order...375lbs, then 427lbs and finally 342lbs"

I realize you are on a G sedan, but your input on how you felt these rates performed is helpful. Are you of the camp now that rear rates less than fronts is advantageous and what are your reasons why? and at any point had you tried rear greater than front rates?

daveh - "the street ride is a little choppy on slow speed bumpy roads" and "skip the upper mounts and re-use the stock rubber bits and you should have a 'decent' street ride"

do you feel these two are related? is the "average" street performance of your setup a function of your upper mounts OR a function of the spring rates/dampers?

thanks

pp

Silverton

Daveh, what springs are you using to get a 0.75" drop? Tires? I plan on running 245/40/18s both front and rear.

I have to admit that your comments that "This suspension ... is just average on the street," and "the street ride is a little choppy on slow speed bumpy roads" is a little un-nerving for a daily driver! This is why I would like to consider a bit less spring rate front and rear than the 500/425 lb springs. Something like 450/427 lbs might be a better compromise, which are stiffer, in the front at least, than the OEM Z springs.

daveh

iTrader: (9)

My comments about the street ride are mostly geared towards the valving of the shock. It's hard to explain, but once the car hits about 40mph, it feels rock solid. The choppyness I mentioned is mostly what happens on the very slow washboard surfaced twisties we have up here in norcal. When the car get's over 40 it soaks up the bumps. I know it doesn't make sense but this his how it feels to me. I can hit a burm at 70 on a track and not feel at all unsettled or jarred. Commuting to work is quite nice. Freeway traveling is better than the stock shocks. I have the 500/425 springs.

Gsedan35

iTrader: (10)

I know exactly what your talking about, and throughout proof of concept work on my Koni setup, I kept finding myself agreeing with your choice of words you used to describe your setup. Though that is not to say that I felt I had a fully "cooked" setup, at 80mph or higher I would get too much front choppiness that was either do to not enough front bump travel where I was kissing the bump stops or the rear oem revised Z shocks were not up to the task of partnering with the front setup. I'm going to order rear Koni's to rule that part out.

Silverton

Daveh, how do you adjust ride-height at the rear without coil-overs? Don't the 425lb rear springs come in a fixed length? If I can run 500/425 lb springs with a drop of 0.50" front and rear, I would be satisfied. I'd rather be at 0.25" and I might consider 0.75".

Gsedan35

iTrader: (10)

Hmmm,.........I'm of the camp that the two rate philosophies will bring about differance's that will mean different things to different people. Here's why I say that.

448/427 vs
448/342

I made no sway bar changes or tire pressure changes.

The 427lbs rear setup was more entertaining to drive around town because the car had less slow speed understeer around town. And even when cornering speed went up a bit to say 45mph, things remained in check. Though, traction out of the hole wasn't as good as it could of been. Higher speed's were met with a measure of oversteer and the need to not overcook things on corner entry. No problem's with drop throttle to report however. Again corner exit traction left something to be desired, vdc engagement is frequent.

The 342lbs setup was not as fun to drive around town because it had more understeer. Though the car was more friendly to throttle imputs or forgiving if you would. It was during high speed corner's that this setup impressed me most. For my taste's a perfect blend of faint understeer and a beautiful amount of grip coming out of the hole, I felt no VDC intervention whatsoever.



When I reinstall my Koni coilover setup, I'm going to try both rates again.

daveh

iTrader: (9)

Silverton, everthing is a compromise when it comes to tracking a car. I amazes me that some people are using street/track brake pads on the track. In my opinion, they do nothing well. They will eat up your rotors when cold and will overheat after 3 laps. Suspension is the same. The compromise of a better handling car is less street comfort. Having said that, the truechoice setup is one of the better track setups to drive on the street because of the huge range of shock adjustment and relatively low spring rates. Since it sounds like ride quality is a big concern of yours, you might just consider starting off with tckline shocks with stock springs. This will still dramatically increase the handling and offer better street ride quality through shock adjustments. You can always change springs down the road.
If you do decide to go with the truechoice's I would strongly recommend going with their default spring rates. Unitech sets up professional race cars. Do not mess with their formula! I'm sure Gsedan35 can attest how difficult it is to get to a good baseline.
When unitech was installing my setup, I asked if a higher spring rate would be better for me since I'm not worried about street comfort. They told me that they tested a variety of spring combinations and found this to be the fastest.
On a side note, truechoice or anyone for that matter should be able to give you whatever springs you wish in the front AND rear. They're just standardized race springs. The rear has an adjustable perch that sits in the rear spring basket. Not sure why they would only change the front for you.

edit: Silverton, what kind of tires are you planning on running on the track. I was trying to get at if you will be running r-compounds.

Silverton

This is the information I got from Pete at TC Kline: (1) they offer springs at 400/425 lbs F/R with 1.0” drop ($289), (2) “We have 2 spring land grooves in the front strut. You can use either the upper (factory location) or the lower (approx 1”) for additional drop if you like.”

From Phil at Truechoice: (1) front springs at 500 lbs and 450 lbs are available, (2) the available rear spring is 425 lbs (stiffness not verified), (3) “Unitech rear setup [Phase 4] has a threaded height adjuster so you can adjust to the ride height you want”, and (4) “They also modify the spring to fit the 350Z so I think if the length needs to be tweaked slightly it should be doable.”

Gsedan35

iTrader: (10)

Very interesting, thanks for doing the footwork and posting what you found out. I'll keep the TC Kline springs in mind if my second go at my custom Koni coilovers still doesn't produce the result's I'm after. Though I do want a wee bit more front spring then that. I can alway's run the front spring perches .5" higher to get just a .5" drop, 1" would be too much for me.

The main reason the Truechoice rear rates peak at 425lbs is their choice in supplier, Hypercoil. That's as stiff as they go in a 5" O.D. spring. Not that I don't totally understand why they didn't source from Eibach, which has the same spring, but in a "sky's the limit" range of spring rates. So I see no reason why they can't use a Eibach ESS spring in the rear with your choice in rate, unless they know in advance that the rear dampner's should not be run higher then 425lbs.

daveh

iTrader: (9)

Updating due to our email conversation. Correction, Hyperco has 5" springs that go all the way up to 1500lbs in 25lb increments. I'm assuming the dampeners can handle a fairly wide range of springs considering that I am in the middle of the rebound adjustment range.

Gsedan35

iTrader: (10)

I talked to pete today and tried to order the springs you talked to him about. At first he didn't know what I was talking about. Then he looked at some notes he had wrote down. Turn's out he wasn't refering to a spring that they have, but that he was guessing at the spring rate of the springs that one of the T2 teams was running before switching to Nismo T2 springs, he thought that other spring was Eibach prokits. This makes some sense, since prokits for the Z are 296/384 front 316/421 rear. Just in case I'm going to call Eibach tomarrow and get the spring rates on their 350Z sportline spring, which I hope is a linear spring, but I won't hold out to much hope for that.


G35 sedan 6mt
Koni coilover front 448lbs
Koni shock rear 342lbs
Hotchkis front bar set to med
350EVO rear bar set to med
Crawford plen
Custom TD injen
HF cats
K&N panel
Rogue short shifter
Enkei RPM2
MX 245/40-18 x 4

palepony

iTrader: (8)

Too bad TCKline don't have those springs. Spring rates close to what I was looking for, linear, but a little too much drop for me.

I believe those sportlines have quite the drop ?1.2inches, but do advise on what you learn about whether they are linear or progressive.

Silverton, what did you decide on doing?

pp

Gsedan35

iTrader: (10)

Well I called Eibach and the sportline's are progressive,...really progressive. Pretty big rate spread 239/400 257/435 Yeah they are a 1.2" drop.