Fletch69z

iTrader: (50)

Thanks! I appreciate your help. The reason I'm looking at the sportline kit is that I have a friend that will sell it to me new in box for 200. So, I was just trying to figure out how much I was gonna have to spend total to get this done. With only a 1.2" drop would my camber be that far off that I would need correction? And about how much will it cost to go this route? Thanks again,
Fletch

ncparamedic

iTrader: (49)

Heres the set up i got with prices. The eibach springs I have seen on ebay (search 350z eibach) for $193 + shipping.

Cusco front control arms - $395 shipped
SPC rear camber arms/toe bolt -$235 shipped
Eibach springs prokit - $220
Tokico shocks/struts - havent got yet but will in a couple..will probably spend $500 or so. So total that is $1350. I also bought me a set of Stillen sways and ordered new urathane bushings for $255 and then $40 for the bushings. Man thats not bad for nearly a whole suspension set up..

fishanan

I am sorry about this stupid question. Which springs are the best (Eibach Pro Kit, Tein S-Tech, or Hotchkis) if I want to lower my car without having camber problems?

changsw

iTrader: (2)

Hotchkis I hear.

punish_her

iTrader: (8)

I know this is not suspention but body Tuning directly relates to handeling and suspention. So how does the GTSPEC line of Chassis reenforcements improve over all handeling of higher (400+) horspower cars? Especialy with TT kits that require the removal of the front brace.

maxflip113

when i lower or raise my car do i also have to adjust the spring like loosen it or keep it the way it was... also do the springs have to be real tight to the upper mount or should i be able to turn the spring with my hand why the perch is tight im so lost.. ^_^

Gsedan35

iTrader: (10)

Ideal spring preload settings are the minimum amount needed to keep the spring in place when the suspension is unladen. So, just tight enough during install so that the spring doesn't move sounds right. Hope you have adjustable length dampners in front however, or your looking at the lowest possible ride height setting, something that you may or may not want.

maxflip113

well the thing is i get a rattleing from my right rear and and i adjust the spring so it was tight enough were i could not move the spring with my hand while the perch was locked. the tighter i go the bouncyer it become i dunno if thats the was its supposed to be but i made the spring so i cant spin it around with my hand. lol im so lost with how to do this

xirtam

iTrader: (14)

If I get Tanabe Springs which lower my rear by 1.2 inch, do I need to get a camber kit? Or just a wheel realignment?

Soundeffects

iTrader: (2)

When do the bumpstops need to be cut?

plumpzz

iTrader: (10)

Are stiffer springs better? I was looking at Nismo T2 springs, and they have a spring rate of somewhere around 600+ lbs/inch. Does this mean that they're better on smooth roads w/ a adjustabile dampening shock like koni's or tokikos?

Resolute

iTrader: (2)

Yes, get a camber kit to bring your tires as close to stock settings as possible. An alignment by itself will not cut it. If you choose to run without the camber kit, as some people do, you will wear the inside edges of your tires faster than the outside, and not have all the traction that could otherwise be available.

Resolute

iTrader: (2)

Preferably never. If you're hitting your bumpstops and you cut them out, then you will simply bottom your suspension and risk damaging something. By bottoming out, I mean your suspension is compressing as far as physically possible, and hitting the bumpstops provides some cusshion when that happens. No bumpstops, no cushion. If you trim the bumpstops, then only trim them half way, and taper them so as to provide some progressive cushioning when your suspension runs out of travel. The ideal situation is to increase your spring rate to prevent your suspension from running out of travel to begin with. The lower your car, the higher the spring rate will need to be to keep you from maxing ouot your suspension travel.

Resolute

iTrader: (2)

Stiffer springs are only better if you need to have minmal body roll and a very low vehicle, aka a race car. On the street, the ride will typically deteriorate to the point of useless as the spring rate climbs. The stiff springs used for racing, like the T2 springs, can be combined with an adjustable damper to help provide some balance by controling spring oscilation while maintaining a softer setting than the stock dampers would. The Koni yellow seems to do well according to several people when combined with the T2 springs to be reasonable on the street. Still, this application is suited more for the track, and should be considered only if on track performance is your priority.
Will

Gsedan35

iTrader: (10)

Well, even with 448lbs spring rates, no dust sheild's to maximize avaliable travel, nice short Jic bump stops, I only had 1.5" of bump travel at static on a 3/4" drop. All still not enough to give enough bump travel. Problem lies in people attributing bump stop issues as totally unrelated issues or just not having the wherewithall to know what's actually going on. To me fair, without dust sheild's and chalking the tops of the shocks, I knew exacty what was going on. Going upwards in spring rate for me is a no win situation as it get's me behond the point of positive returns do to local road condition's that I like to play on.

downforce

I've noticed that the stock spring rates are higher in the rear;

OEM Front:314 Rear:342

and few coilover suspensions;

Nismo F:449 R:506 F+43% R+48% Transfers +5% roll stiffness to rear

Jic Flta-2 F:560 R:672 F+78% R+98% Transfers +20% roll stiffness to rear

Both known for track performance.


From the information that I have gathered the 350Z has understeer, which can be overcome in different modifications and combinations of modifications. Such as increasing tire width and inflation pressure in front only. Adding adjustable sway bars and changing them until the desired grip is achieved. Getting a performance differential like Quaife which will transfer more power to the tire with the most resistance/grip (the outside tire in a turn) compared to normal limited slip diffs which tend to make the car go straight. And then there is the spring rate to consider.

Like I mentioned at first the known track worthy suspensions tend to transfer roll stiffness to the rear unlike the majority of the others out there. I have also read that, “If the car is understeering, there is either too much wt transfer on the front outside tire or too little on the rear outside tire. A less stiff sway bar on the front will relieve some of the wt transferred to the outside tire, and a stiffer sway bar out back will increase the wt transferred to the rear outside tire.” To add to that I have also read that you should, “Set the car up via spring rate tuning first, then fine tune with sway bars. Sway bars are not meant to leverage large amount's of roll stiffness to overcome poor spring rate tuning, they are meant to fine tune at the limit balance/behavior on a already well sorted chassis.”

After digesting all of that, my question is this, wouldn’t it be better to select a suspension who’s spring rate adds roll stiffness to the rear like those mentioned above and add adjustable sway bars to fine tune, with maybe some of the other methods to help reduce understeer?

Gsedan35

iTrader: (10)

I understand your rational, I was being lead down the same path at one time with my car. However, the rational behind the Unitech race team's reasoning in R&D'ing the Truechoice coilover product and why they went with a 500/425 spring rates won me over in principle and in my own back to back testing. I know tuning theory say's to not run so much front rate. Yet for whatever reason maybe the dynamic things one can't predict like overall suspension design or bushing compliance, it works better. In the end, one is supposed to go down their own testing path, perhaps that will see you stick with a rear biased setup, equal or a front biased setup, so I can't harp on right or wrong, only what my own testing said to me.

https://my350z.com/forum/showthread....ght=truechoice

Resolute

iTrader: (2)

To answer your question: Yes, you understand perfectly the conventional wisdom for suspension tuning. And props on grasping the difference on handling a clutch LSD will make vs a geared unit like the Quaiffe. Very nice.
Now the bad news: conventional theory doesn't make the best suspension on the Z. You always want to run as light a sway bar as possible for track use, since the bar will remove traction from the outside tire. Therefore, the conventional wisdom is to run as high a spring rate as possible on the driven end of the vehicle to keep both outside and inside tires as planted as possible for acceleration.
However, the Z has an abnormal amount of anti-squat and anti-dive in it's suspension. That rear "traction rod" that everyone pisses on about is part of the anti-squat design of the rear suspension and transfers a very high amount of weight to the rear on accel. This allows the Z to have traction for acceleration without using springs stiff enough to jar out teeth fillings. The problem is that it also means to keep the car flat through a turn it uses pretty big ant-roll bars. Because of the anti-squat engineered into the suspension, if you raise the spring rate too high out back you'll have wicked oversteer on acceleration out of a turn, and possible wheel hop if you're not careful. This is why convention doesn't always work every time.
The Z will do best with a lower rear springs rate than the front, just as the Unitech boys found out. Now, you can always cut off the mounts of the traction rod and the upper control arm, and lower the mounting points by re-welding them. I have seen this done. The Opera Performance Z is a good example. But is it worth all that effort? Not to most. Get the Truechoice suspension and have them sub in Koni 2812's for the dampers, and you'll have a more thoroughly tested and tried suspension than everyone else at the track.
Happy driving,
Will

downforce

Great reply.

A few more questions.

What about front to rear balance, if the rear is that much softer a lot of weight will transfer to the rear during acceleration and cause the rear to squat upsetting the balance of the car, so would you corner weight the car with a higher percentage forward like 55/45 or greater to retain a close to 50/50 balance under accel, or do you really want that much more weight in the rear?

Also what about roll stiffness, since so much is being transferred to the front wouldn't that require a stronger rear anti-roll bar to keep the rear planted or is the structure of the car rigid enough that the added stiffness in the front will keep the car flat and from rolling too much?

One more, with a staggered set up with wider tires in the rear and a diff like the Quaife, is it still recommended to soften up the rear? Or would you want to keep the spring rates equal front & rear so not to create more oversteer?

I want it to be fairly neutral handling with mild understeer at the limit, with power on oversteer, mostly driven on the street and see some track use hopefully. I am terribly analytical about everything, over thinking stuff to death, it's just, what i do.

Thanks

Resolute

iTrader: (2)

Ok, let me clarify something. I did say earlier that the anti-squat and anti-dive on trhe car works to transfer more weight to the front and rear under braking and accel. This is not technically correct, but it is easier to understand than saying that it effectively increases the wheel rate at the front and rear. Since you are interested in some of the more technical aspects of this, then let me be a little more precise.
The weight transfer taking place in a car is only dictated by the hight of the center of gravity in the car, the wheelbase and track width of the car, and the over all weight and its distribution in the car.
Spring rates and anti-squat, roll bars, etc.. do NOT alter the weight transfer taking place. They alter the contact patch, camber curves, and effective wheel rates to improve or otherwise alter available traction at their respective tire(s).
Keeping this in mind, your corner weights should have an equal wedge front to rear. That is, they should have equal weight totals in a diagonal pattern, FR to RL, etc.. There is no point in increasing spring pre-load to compensate for weight transfer due to a relatively softer spring rate out back, since spring rates do not affect weight transfer.

Keep in mind the "softer" rear spring rate used by unitech is still stiffer than stock, but not to the point of causing throttle oversteer issues or wheel hop when trying to exit a turn. A stiffer rear spring can be, and has been, used for the rear of the Z. Just remember that while the stifffer spring helps keep the car planted in a turn, it also requires better throttle modulation to avoid oversteer. The Unitech rates were seen as the best compromise. The softer rear springs will also work better to keep the Z's rear tires planted over rough pavement than a stifffer spring rate otherwise would. A stiffer rear bar is going to be used to keep the car flat, though. The Z is a very stiff platform, but no car is going to be able to use front roll stiffness alone to avoid the torsional effects on the chassis in a turn from impacting the rear. Either higher springs alone will be used (ala Exige), or springs and a roll bar (ala everyhting else). The Z is of the latter catagory.

The Quaiffe, lower rear spring rate relative to the front, and larger rear tires will increase the tendancy for understeer, and limit your oversteer. The devil will be in the details of roll bar stiffness and damper tuning. This isn't as hard as it might seem. The Quaiffe is still going to give you less corner entry understeer than most LSD's, and always run as wide a tire as possible and tune your balance with the suspension. Remember, a larger bar will lift on the outside wheel, reducing the wheel rate drastically and create more roll couple. So a larger rear bar will help with corner balance, the lower rear spring rate will help with traction over surface irregularities and maintain traction on accel out of a corner. Good dmapers will control your spring loads under weight transfer from getting out of control and allow the weight to go where it should as quickly and as smoothly as possible. And the larger rear tires will ensure there is adaquate contact patch to put the power down as well as finish your turn. All the ingredients are there for the Z to have a world-class handling car, and the parts are readily available, you just have to decide what you want. I think I have already made my preference obvious, but look around and you'l find some good designs to pick from.
Will