The springs need to have one open end and one closed end. You cut the open end and rotate it on the closed end. In this case there's no issue with how the spring will sit in the perch. If both ends are open, you need to be able to rotate at least of the perches to have the spring seat properly.

Okay makes sense.

I am now legitimately interested to see how this turns out now.

As far as I can tell based on data I've found and looking at the springs themselves, they are not progressive. Where did you get information that suggests they are?

I'm not interested in the residual value of my vehicle, I am interested in customizing it to exactly the way I want it to perform on the streets that I spend most of my time driving on. One of the nice things about there being so many affordable out-of-the box solutions, is that there are tons of oem springs floating around for free or next to nothing. I have a free standing spring compressor and a garage, so swapping springs doesn't take me much time and I could easily go back to the stock suspension prior to sale if I wanted to.

I guess honestly I just assumed they were progressive. Thought all shock springs were, that's why companies sell Swift springs right? Anyways, I commend your attitude on personalization as I do things the same way.

EDIT: You also make a good point about cheap springs and having a place to work on them. But really, why not just buy a set that's already stiffer and engineered to work properly? If the springs AREN'T progressive your ride heightwill be lower but your spring rate won't be higher, you will bottom out more and put excessive strain on your shocks

So I found some good info ( http://www.bluecoilspring.com/rate.htm ) and created a calculator in Excel. Using pictures of the stock springs and the known values published about them, I was able come up with reasonable estimates and tweak it to produce the factory specs. Then I'm able to "remove" coils and get the new spring rates.

What I found was that cutting .5 coils off the front will increase the spring rate from 153 to 170 and cutting the same of the rear will increase from 195 to 215.

Ideally if I could figure out how much coil to cut to achieve my targeted ride height, then I could plug that amount in and find my spring rate. Unfortunately it seems like it would be incredibly difficult to accurately calculate that and it would probably be better to start experimenting if I want to move forward.

The utility of progressive springs is one of the arguments for buying springs. I like the feel of a stiff dampener combined with a progressive spring, it allows for good handling on less than perfect road surfaces.

Spring rate does go up as you remove coils, the question is whether or not the spring rate will increase enough at the desired height

Compare your calculations to other aftermarket options

I definitely will, I would just need to figure out the ride height change to have the complete picture... I know what cutting half a coil will due to the spring rate, I don't know yet how much drop it will yield.

So cut off .25 and see where it sits?

That's a good starting point. Also I'm not driving my BRZ in the winter, so I have plenty of time to play and tweak.

Go find a local giving away or selling their springs cheap so if you mess it up you got a fall back

FWIW, the book "Race Car Vehicle Dynamics" by Milliken and Milliken was written in 1995, and is still considered the suspension 'bible'.

Let the hate flow
 

Every time I see the title of this thread I just think of,

http://cdn.meme.am/instances/500x/23921834.jpg

Even in his voice too.

The thought process brought to you by spider man!!

Step1:
http://cdn.meme.am/instances/500x/58357613.jpg

Step2: Cut springs, Go for test drive
http://i.imgur.com/byiRi.jpg

Step3:
http://i1.kym-cdn.com/photos/images/...82/121/3f7.jpg