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Discussion Starter · #1 ·
So like the title says I'm trying to match rates on a bastardized ISC N1 Street and Comfort set of coils. I bought this car with these already installed. On the highway and well maintained surface roads it's fine. Not until I started pushing it on roads I'm comfortable with did I realize how messed up the rates are. Initially I thought it was just too low and damped too stiff because I was mainly focused on the rough ride on potted roads, also the mild stance. Bet you didn’t know 9.5 et10 fits on all fours lol

Symptoms:
Bouncy ride
Harmonic oscillations (think of a bouncing ball losing energy)
Control arms slamming into bump stops on rebound
Wicked snap oversteer while cornering or hard throttle on an uneven surface

Turns out I was wrong about the stiffness, bouncy bounce ride should have been all I needed to listen too. From what I've been able to learn working with ISC, they've been great btw, is that this set was made before they started to offer a kit for the ST. I have street and comfort damping with 5k front and 4.7k rear springs. ISC recommends an 8k front and 5k rear, which from reading up on the subject is opposite of the factory bias. Swift Springs, who ISC recommends as an upgrade, has the Spec R springs which are essentially stock rates at 251 front and 279 rear.

I have tried some different valving combinations over the last several days with various levels of “success”. The PO had the shocks/struts set at 13 all around. Right now I’m on 25f and 31r, out of 32. This is a big improvement, crisper turn in, less bounce but not eliminated, moderate steering feel, better poise and balance overall. Still too bouncy, rolls in the road at speeds around 10-30mph and I’m doing my best low rider impression, over 35mph it's a near lift off and/or hard slam.

So with that I feel it's the springs and the right damping is in there somewhere, just not with the current rates I have.

I think returning to the factory bias of 60/40 (Thanks to some very informative posts from @XRJoe) is my best bet in finding the performance I’m looking for. I want less body roll and more taught suspension then the stock setup, while keeping a smooth oem quality ride of a daily driver. I don’t mind road noise so much but the jarring slamming and bouncing afterwards is not what I want at all.

I’m looking at Swift Springs with 6.5k/364 front and 8.5/476 rear springs. At 6.5/8.5 it's an increase of 37% and 58% over stock and 30%/80% over my current setup.

My main concern is if this is enough spring up front? Should I look at stiffer fronts? Maybe 7/8.5 or 7/9?
Are Swifts really that much smoother on rough roads?

Any input or comments are appreciated.
One last thing to add. I plan on getting wider wheels in either 17 or 18 so I can run 255 wide tires.
 

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Discussion Starter · #2 · (Edited)
Nobody is running rates with the factory bias?
Anybody with Swift Springs that can attest to the smoothness or hype?

Now I'm looking at using a 7/8.5k combo instead, or 392/476. I made a crappy spreadsheet on my phone and I like what the increase over my current setup looks like, 40% increase front 70% rear.
 

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Im running the swift spec r's on bilstein b8's. Yes the proper bias makes a difference. Im either winning or runner up in my auto-x class, car rotates beautifully, rides smooth, but slightly stiffer even with the 4.5k/ 5k rates the spec -r's are rated at. @UnfocusedST is running swift 6k/7k on his ycw coils and he seems to like them as well.
 

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Discussion Starter · #4 ·
Right on, thanks dor the input.

So even at 4.5/5 it's an improvement? That's good info. I have been concerned about going to soft so that's why I'm looking at 7/8.5 now. With the 5k ISC spring up front it's very bouncy, it's still very controllable but not exactly what I want. It gets a touch unpredictable with the setup I have, I'm basically using the shocks to compensate for the soft springs. With this out of balance, compensation set up, on public roads, it's very difficult to narrow things down.
 

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Yes but keep in mind Im not as low with the swift spec r's, and I think with these rates, this is the lowest you can go while maintaining proper suspension travel. Any lower and the car would feel undersprung, probably similar to what you are experiencing right now.
 

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Discussion Starter · #6 ·
That's a good point you make. I'm at a 1.625 drop in front and 0.75" in the rear, that doesn't sound like a lot to me but with this setup it's far from ideal. I just got the adjustment spanners in hand and hope to raise the front this weekend.

Where can I find information on the stock lengths and how much supsension travel there is stock? I've searched but come up empty.
 

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From what I remember @oinojo did some extensive research when he was still competing in his FoST and from what I remember, the FoST in stock form already has very little amount of suspension travel. If you look up his build he has some info in it.
 

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You can't just change the springs, and expect better. It won't work, and you'll be dissatisfied more than likely.

Here are a few points to consider...

Picking on the ISC valving, it in itself I bet is wrong. Thus the case with 90%+ of the cheap Taiwanese coilovers saturating the market.
Typically when changing springs, you can only go +/- 2k in rate, before a shock needs to re-valved, the manufacturer can confirm that variable.
Swift springs are an awesome thing, as are Eibach and HyperCo.
There is only one setting (coilover adjustment setting) change that is perfect for a particular spring rate.This will remove the oscillations, no pogo'ing, and offer the most comfort.

The first two points I've outlined above will prevent you from reaching the perfect/ideal setup.

Is there a cheap alternative? No.
You either get new springs, and a proper revalve from someone that knows WTF they are doing. (e.g. Feal Suspension in SoCal)
Cut your losses, sell it, and look at an ST/KWv1 setup, Bilstein, Koni/GC, Eibach coilover setup. All affordable options with proper valving and spring rates. YCW seems mid-range, and then there is the KW v3 on the higher end, or if you're baller, get the new KW DDC made for the RS (bolts into an ST just fine), and buy the optional DDC controller
 

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Discussion Starter · #9 ·
That has been in the back of my mind. First thing I did when I started to consider running a ratio similar to the factory was ask ISC if they see any issues. As a layman I figured there is enough adjustment in the valving but without direct knowledge I am unsure. While the ISC reps have been very helpful tracking down what's installed on the car they haven't beem as willing to discuss the valving and have nit been receptive to the idea that the ST should not have stiffer front springs. The ISC kit uses 2 different valving options with the same 8k/5k springs, with overlap in the valving between the street and comfort sets. I don't want to speculate but I have worked in manufacturing for 15+ years and based off that alone I wonder if they just use a different PN?

At this point I will have a closer look at my options. Of course I would love to just swap springs I don't need height adjustment and would be served well with a matched set of struts and springs.
 

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The Bilstein 814 is just a B8 in coilover form. It's affordable too for a coilover. The B8's with a proper spring are prety nice too (I have that with KW springs, which are no longer made) It's got about a 10-15mm drop and a slightly stiffer rate. But the valving on the B8's are awesome. Rides more comfortable than stock, yet firmer, with the right amount of spring control needed.

If you don't need height adjustment, go B8 + springs.
 

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Discussion Starter · #11 ·
The B8's are an option I'm considering.

I'm looking at $540 to change springs and the rear perches. ISC uses a straight coil at 84mm ID in the rear, the adjustment perch is on the bottom.
Add another $500 if I end up having the struts/shocks revalved. I could look to do this myself now that I'm thinking about it.
 
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