So I'm getting a set of koni yellows and I'm looking for the best spring to match the shocks.

I do probably 70% autox / 30% HPDE. Looking for a 0.6-0.8 drop.

Read that linear springs are better, but there aren't that many options for linear springs out there. Discussed with GSedan35 and he recommends the Tein S-techs (which I am highly considering based on his recommendation).

Just wondering if anybody else has different opinions / suggestions

As a reference, I SEARCHED and found this really good thread showing spring rates:

https://my350z.com/forum/brakes-and-...-coilover.html

Also what confused me is a lot of the lowering springs go stiffer in the front but softer in the rear, any reason y?

Thanks!

 

I've been going through the same stuff lately, and all the feedback I've gotten from people I trust and know their stuff has been that the street/tuner progressive stuff isn't really up to the job of serious autocross and track use. It will work, don't get me wrong, but it's not what you'd choose to go 100%. Just repeating what I've been told though, no firsthand knowledge yet.

As for why the stiffer front/softer rear, it could be a number of things, but from what I understand of suspension tuning and setup, that would provoke more understeer/reduce oversteer, which might be a lawyer-move to reduce risk, or it might just be preference. Other than that, I can't see why anyone would go softer than stock, though I've also seen little need to go much stiffer in the rear - it already rotates nicely.

 

From what I've seen, unless you pony up for SCCA T2 springs (Nismo springs) then you aren't going to beat S-tech's easily.

I'm happy with the setup I purchased off GSedan35, that uses a generic spring in the front with new lower spring seats.

 

Yeah, but unless he is getting his shocks revalve to those T2 specs, he will destroy those shocks easily.

To OP, I was also looking at a koni setup for autox/drift/hpde/drag. I also wanted at least an 1 inch drop all around that are on linear springs and stiff rates. I searched and searched, a lot of people run RSR springs with Konis and they liked it a lot.

Since they didn't offer that much of a drop I searched on and decided to go with whiteline as the spring rates are 365/445 and offer 1inch drop in the front and 1.2 in the rear. A site sponsors sells them for 280 shipped. I also contemplated on D-spec shocks/springs setup but I decided to go with Koni instead.

 

I, too, like my rear springs a lot softer than the fronts. A few of our local autox guys like the linear springs with their Koni yellows as well.

 

yeah I thought about T2 springs, but like drifter 5 says, I'll probably have to get the shocks revalved to match the higher spring rate.

Guitarist I understand what you're saying, but from my memory you're skill is on a national level while mine is still barely on regional haha. So I don't mind saving some $$ while I continue to improve the driver (just gotta give him a boost in confidence every once in a while). And I understand the understeer comment as well. I guess I can tune with my swaybars if needed.

I'll look into the other recommendations posted. Anybody else?

edit: Scott which springs are you running? And which linear springs are the other guys running? Thanks

 

Thanks for the compliment, but I'm (or my car is, maybe a bit of both) a good second per minute off true nationals-level skill/pace.

I totally get the money-savings aspect though. Spending half as much money to get 90% of the performance is a good bargain. And tuning with sways is a good approach to a street-driven car.

 

Regarding front and rear spring stiffness. The reason why road cars have higher rear spring rates or wheel rates is because when you hit a bump the front suspension hits first and then the rear hits shortly after. The stiffer rear spring has a higher natural frequency which means its oscillates up and down quicker than the front. Since the rear hit the bump after the front the rear tries to "catch up" to the movement of the front suspension. Your car will tend to move up and down with little pitching movement as a result.

High performance set-ups usually have stiffer front springs, wheel rates and roll rates. The driver reactes to the axle that loses grip first. Therefore you would rather have the front axle lose grip first because you can actually control that axle with the steering wheel. Also, as you approach the apex of a corner you want to be in slight understeer (excess rear traction). This will enable you to power out of the corner. If you were neutral steer or oversteering at the apex you will not be able to put power down because your rear tires are already at the traction limit. You will simply spin. I think they also use stiffer front wheel rates to control roll in corners and keep the contact patch as large as possible without rolling tires over onto the sidewall. I may be wrong about this.

Perhaps some of the suspension guys can elaborate on my post or make necessary changes if I made any mistakes.

 

You made a lot of broad sweeping generalizations that I don't see holding true (especially thinking about other cars).

The first thing I'll note, is that the Z has effectively a double wishbone front and rear suspension (sortof) with a rear anti-squat/dive bar (radius rod) integrated into it.

Second, is that in general, while sway bars are important to handling )you want dive and body roll to be minimized but somewhat equal, you have more lever length on dive prevention than roll, so you need to increase roll stiffness with a bar), it is important to also tune as much as possible with springs. Using a sway bar for tuning removes a large deal of the "independence" of the suspension, a bump on the drivers side will unsettle the passenger side as well.

The anti squat/dive system on the Z effectively increases the spring rates in the rear under acceleration, and decreases the spring rates in the rear during breaking, reducing the need to run such stiff spring rates for street use. Unfortunately this can make it difficult to pick spring rates for the Z, as going stiff could result in an overly stiff setup, and going too soft requires a really stiff sway bar. There have been modifications made to reduce the assistance of this rod, but they aren't street car or SCCA classification friendly.

Stock the rates are something like 1200 lb/inch front and 400 lb/inch rear for the sway bars. I don't want to significantly increase the front bar, so I went with the 448 lb/inch tien tapered springs (90-70 mm taper, 250 mm height) that GSedan35 sold me, with a flat plate aluminum front mount (that he made, seems pretty easy to make if anyone wants any I'll have a machine shop cut a set).

This with stock rear springs and cut rear spring seats the car handles great. The drop is ~.4 inches (can go lower if needed), and the spring rates are fairly appropriate. However, I'd like to run a stiffer rear spring with revalved rear shocks if I could, with the inboard mounted rear I have a lot more front stiffness than rear, and have to compensate with a lot more shock dampening to keep the rear planted.

 

I run the RS*R Ti2000 springs with my yellows and love them. But the springs are within 10% of the stock spring rates, and linear.

 

Sure I made a lot of assumptions because I didn't want the post to be too long and because I'm not an expert. I was simply trying to explain why road cars have higher wheel rates in the rear. And the answer to that has to do with the higher rear natural frequency to keep pitching to a minumum when hitting bumps. I'm sure there are more factors involved but this is probably one of the more important ones. Peak350 I don't mind you pointing out any mistakes I made. I'm here to learn as well

 

Not all factory cars have this, was one of the key things I forgot to note (I got interrupted when I was writing that response and just finished my last thought and posted).

The use of the car within the realm of motorsports will dictate what spring/shock package will work best. I'm essentially running a stock setup, I've just stiffened my front springs which pretty much eliminated dive and body roll, I run really stiff on my rear shocks, about middle on my fronts. This results in the car staying fairly planted, the rear isn't able to transition as fast, keeping weight on the outside tire, and allowing me to maintain some ability to accelerate out of tight corners. Now, note, this is autox, if I was on a larger track, less rear stiffness would suit me well. The things I am fighting most on course would be solved by stiffening my rear spring rates a smidge (say 550 instead of the stock 430ish), but the expense of doing so outweighs the benefits I'd gain. Mind you, right now, my car rides perfectly fine.

 

True, all cars are different. I was being quite general. I haven't started playing around with the 350 suspension yet. Probably won't for a couple years. I'm having enough fun with a few track days a year. Might just wait until I gut the car to really dial in the suspension.

 

In for updates and opinions

 

T2 springs have no business being mated to out of the box Koni Yellows

To the OP - the S Tech is without question the best bet, and will compliment the yellow's very well

 

Right, I forgot to note that I would have the rears revalved.

From what I've gathered from various sources, the Koni's shouldn't be matched with more than a 450 lb/in spring rate without being revalved.

And I would also go S-tech if I wanted more drop, its something I've considered switching to as the minor loss in spring rate is not something I'm sure I'd notice.

 

No one can say to another, yeah you have to run this spring rate or that rate. But I tried the Koni's with 448/500. Yeah it would rotate more easily. And the rear shocks felt fine as far as rebound control goes. But, I had less traction comming out of the hole and had to continueally delay when I could roll into the throttle as cornering loads eased. Nor was I able to carry any more speed mid corner vs the 427lbs rear setup. This is exactly what Unitech Racing found out when they set the spring rates for the Truechoice coilover suspension. I've tested a lot of rate combo's and no I won't say it was a track enviroment. Let's just say I have a nearly deserted mountain road that has good line of site and only my pride to damage if I mess up. But, again, no one can tell someone else what rates they should run, I can only relate my experience. It's up to each owner to decide what is a plus and what is a minus. I actually revalved my Bilstein Pss9 setup to run 560/500, moreover to keep roll couple in check (more even wheel rates front to rear). But I have since stepped down to a 450lbs rear rate.

Having run the Koni's with a 560lbs front rate, it was a bit too much for the shocks and had I not ordered the Truechoice setup I would have had the front's revalved (ran 427lbs in the rear so they were fine).