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post #11 of 175 (permalink) Old 11-12-2013, 11:06 AM Thread Starter
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I've read about but don't really understand the math behind that frequency stuff. I leave that to those who really have a grasp of the concept.

One thing I do recall reading about that formula is that many forget that the ratio of the rear springs is altered by their positioning on the lower control arm; it is not a 1:1 ratio, and I do believe that this factors into the frequency equation.

So a rear spring rate of say 525 is actually more like 420.

Yes?

And as far as front camber goes, many of us have had zero to minimal front camber for a long time. Some have gone to the Corksport camber plates recently, and I think even more will jump onto the Ground Control simple camber plates (one piece!) once they are out and available. Keep watching their website!

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Originally Posted by color0 View Post
I still think some of you guys are nuts running those springs in the rear. The natural frequency of 450lbs/in front springs on a 2.0L 3 is just below 2.1Hz. The same springs in the rear will hit almost 2.3Hz. 525lbs/in rear spring brings that to almost 2.5Hz. Unless I'm running the numbers wrong, even a 450/525 setup is worth a 17% rear bias. How do you guys drive 400/525? Do you have no front camber???

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post #12 of 175 (permalink) Old 11-12-2013, 12:34 PM
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Quote:
Originally Posted by mazda3az View Post
One thing I do recall reading about that formula is that many forget that the ratio of the rear springs is altered by their positioning on the lower control arm; it is not a 1:1 ratio, and I do believe that this factors into the frequency equation.

So a rear spring rate of say 525 is actually more like 420.
It's more than that, closer to half.

The ratio in the rear is about 1:0.71. In the equation, the ratio is squared and then multiplied with the spring rate. 0.71 squared is 0.50 (half). Meaning a 525 lb/in spring at 0.71 ratio is only putting half it's force on the wheel per inch of wheel travel, or 262.5 lb/in at the wheel.

The ratio of the front is 1:0.95. 0.95 squared is 0.90, so it's force on the wheel is only 10% under the actual spring rate.

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post #13 of 175 (permalink) Old 11-13-2013, 09:45 AM
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yep, the magic is in the motion ratio, think how easy it is to cut a wire coat hanger with wire cutters. the mechanical advantage of the rear suspension requires the higher rates.

scott, could we get some pictures of the perches? I am curious from the image on GC's website, does the threaded collar hold the upper or lower spring perch?


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post #14 of 175 (permalink) Old 11-13-2013, 11:19 AM
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Can someone tell me what the oem spring rates are and cite the source with a link? With a search a while back I came up with 150f/130r but that doesn't make sense to me given the motion ratios. Wouldn't it be 130 up front and 150 rear? Perhaps those numbers aren't even correct at all. I'd like to know the starting point and what type of front/rear balance my car currently has on stock springs before changing anything.

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post #15 of 175 (permalink) Old 11-13-2013, 11:59 AM
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Those numbers sound right Adam.

[street] Cars are meant to understeer, not oversteer.
Also all of the weight is up front, so springs are there to hold up the weight, not performance.

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post #16 of 175 (permalink) Old 11-13-2013, 12:08 PM Thread Starter
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Stock SpringRates and GC Coilovers

No link, but after many searches I also found the stock spring rates to be:

Springs
Stock MZ3 ..........................150/130
Stock MS3 ..........................188/171
Eibach ProKit .......................160/171
Swift ..................................252/252
GroundControl/Scott.............400/525
Ground Control "Aggressive"....525/650

The ProKit and GC seem to have the best handle on the rear spring rate differential.

Here is a pic of where the GC sleeve will be going when I get a weekend free (on the shock body just up from the lower perch seat:



I had to remove the gland nut lip first (shiny area). GC states that they believe the newer shocks no longer have that lip, or perhaps it's only the MS3 Koni shock that does not. No one knows for sure....yet.

The stock upper shock mount (insulator) is used in the GC Coilover install. You pop off the stock bearing from the insulator, and theirs goes in it's place.

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Originally Posted by Adam3s View Post
Can someone tell me what the oem spring rates are and cite the source with a link? With a search a while back I came up with 150f/130r but that doesn't make sense to me given the motion ratios. Wouldn't it be 130 up front and 150 rear? Perhaps those numbers aren't even correct at all. I'd like to know the starting point and what type of front/rear balance my car currently has on stock springs before changing anything.

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Last edited by mazda3az; 11-13-2013 at 12:09 PM. Reason: spelling
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post #17 of 175 (permalink) Old 11-13-2013, 12:55 PM
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Originally Posted by mazda3az View Post
The stock upper shock mount (insulator) is used in the GC Coilover install. You pop off the stock bearing from the insulator, and theirs goes in it's place.
Hope you'll bomb us with pics when you start installing. Glad it's working out though.

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post #18 of 175 (permalink) Old 11-13-2013, 02:03 PM
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I don't think I knew that the pro-kit rates were so low, I thought they were low 200s! Makes me that much more excited for the GC set-up.


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post #19 of 175 (permalink) Old 11-13-2013, 02:08 PM
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I was surprised the rear was more stiff.

That said, the spring rates on all "easy" aftermarket spring setups are pretty low, I think the Megan "race" springs were the highest I could find and they just peaked over 200lbs I believe.

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post #20 of 175 (permalink) Old 11-13-2013, 02:24 PM Thread Starter
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Aftermarket Springs vs GC Coil Overs

As far as I've been able to gather, most if not all of the aftermarket springs previously made for our cars are pretty much "lowering" springs, which are mostly for appearance rather than actual performance (IMO). If there was any performance advantage to them, it was pretty much an afterthought.

I am thrilled beyond belief that GC has finally added the MZ3 to their list of available goodies. I jumped right in.

I'll be on the ProKit front springs for a few weeks and events (until I have time to complete the install). Previously I was running a "cut" set (-1.0 coils) of MS3 springs in front, and stock MS3 springs in the rear (same rate as the ProKit).

My hope is that compared to the handling I had before, that this temporary setup will turn in better, and the rear may loosen up a little . My Hotchkis big rear bar has been on full stiff.

Against a local group usually with two or three National Champs (Peters/Zust/more) I'd usually been Paxing (in STF) around 930-960 with 7"x15" wheels and essentially stock springs with no camber. I am really curious as to what real springs will do for me....and some camber.

Yeah, I'll be taking/posting more photos in the near future.

Quote:
Originally Posted by XCNuse View Post
I was surprised the rear was more stiff.

That said, the spring rates on all "easy" aftermarket spring setups are pretty low, I think the Megan "race" springs were the highest I could find and they just peaked over 200lbs I believe.

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