Is our suspension setup correctly by aftermarket strut MFR's? Is the bias correct?

**J. Fast** · 07-17-2013, 09:26 AM

Something doesn't look right to me regarding the dampener plots Nihil posted. It's typical to see more rebound bias in dampeners to offset the springs. Compression dampening typically dampens unsprung mass and rebound dampening assists sprung mass. In a two degree of freedom system the springs and dampeners are coupled in compression so the rebound force should equal the total opposing forces. Is this not correct? The Megan dyno plots appear to be way off. They bias for compression (positive force on the shock dyno) and do not account for the weight of 1000lb corners coming out of compression. They only bias rebound for around 150lbs of force?

**Nihil** · 07-20-2013, 11:48 AM

That's what I was wondering...Kinda understand the graphs, just don't know what good vs. bad is. So what you're saying here, is, and as I observe it, compression is going to be stiffer than the rebound, so, it'll take more force to compress and less to rebound, slower compression stroke and quicker rebound stroke, correct? Yours show closer to a 50/50?

Speaking from moto suspension, you typically run a more firm compression and less firm rebound, to get back to full stroke quick enough to absorb the next obstacle, though cars aren't going through as much obstacles unless offroad. So I don't know how far off meagan is or what's good vs bad.

**J. Fast** · 07-20-2013, 08:22 PM

Here's a few alternatives measured and spec'd to our chassi.

Fortune Auto 500 series: 91-99 Z15A Z16A Mitsubishi 3000GT 4WD 500 Series - Fortune Auto Coilover Superstore

Bilstein:

Their bias to rebound is significantly different than the Megans. Megans are opposite.

**Nihil** · 07-20-2013, 10:01 PM

That makes more sense for a car. Though, what spring rates are their valving charts set up for? I'd think, with a car, the suspension is a lot slower so more rebound vs compression would make sense

**J. Fast** · 07-20-2013, 10:26 PM

When you compress a 600lb spring 2" you load 1200lbs on it. You want to have the rebound bias to unload the spring smooth so you don't blow thru the valving. The bilstein plot is for stock springs. 300lb springs with 100lbs of compression so like 400lbs till rebound blow off. If you install double the spring rate you want to double the valving. No shocks on the market do that. A 700lb spring should have rebound bias atleast equal or greater. Megans are not an upgrade when I look at the dyno plot at all. They have no bias built-in to unload the springs. They are too soft in rebound to hold the corners down. On paper they appear to likely induce bounce.

**Nihil** · 07-20-2013, 11:23 PM

I agree, they seem to be bouncy. I'll have to track down more graphs for the other common brands.

**familyMAN** · 07-21-2013, 04:19 PM

First time I have seen the fortune auto. What do you think about those as a budget coilover?

**J. Fast** · 07-21-2013, 10:26 PM

Fortune valving looks pretty good.

I found another shock dyno online published by Fat Cat Motorsports with valving for off the shelf JIC FL2- TAR's for the Z16A (2006). I can translate it using the averaging method and re-plot on a standard shock dyno graph.

From what I'm seeing on the graphs, the JIC hysterisis is really small and there's not big spikes or anything. My take after seeing the empirical data is Dennis Grants little rant regarding aftermarket suspensions a few years ago was a little hyped. I could see it being justified with the Megan's because the valving is absolutely miles off for the spring rates but for the most part every dyno plot posted in this thread (with the exception of Megan's) looks pretty good.

Here's some more good info and a full cycle plot of JIC's not using the averaging method.

EDIT: I also forgot to mention I have dyno plot info on the TEIN EDFC adjustables as well. If I get some time I'll post those charts up also and combine everything for our specific chassi on one dyno chart like the dyno take 2 Toni has, except it will be for dampeners (hopefully fronts and rears). KW's and Ohlin DFV's... I have that data also

**J. Fast** · 07-22-2013, 07:28 AM

Here's some empiricals from Greg Haye @ GT Motoring

This first average plot is for off the shelf KW's. Blue line is the front and the Black/Grey line is for the rear.

These are Ohlin DFV off the shelf valving. Blue line is full soft with low speed bleed in road setup. Grey line is full hard in track configuration.

Fronts:

Rears:

KW's front to rear's look like they might be difficult to phase together. Off the shelf Ohlin's look much better and are closely resemble the valving for my JRZ's and Muellerized setup on my red 2G.

I've never been in a KW appointed 3/S but have some immediate questions with the front to rear progressive/digressive bias. Anyone have any ride and/or track feedback for the KW's?