02TransAm/Batmobile

iTrader: (32)

Hey guys, I'll be switching my Strano's to stock springs soon and I've always wanted to know the actual spring rate of cut stock springs. Well I finally found a shop nearby that tests spring rates and we'll all finally know soon. I think the unofficial quote is roughly a 10% increase for every coil you remove. Let's see how true this holds up.

Stay tuned!

Flubyux2

I'm interested.

My buddy just did 2 coils off the front of his z28. It was crazy low... Basically too low to drive. So I'd say between 1 and 1.5 coils ought to be safe. It'll be nice to know what the spring rate becomes.

Sam Strano

iTrader: (41)

The rate change is dependent on how much of the working spring you remove. If there are 10 working coils and you take 1 out, that's about a 10% bump. But 1 coil on a 12 coil spring is less than that.

Also you need to test that very spring before you do anything to verify the actual rate, and you need to make sure you testing working rate on springs that are progressive.

02TransAm/Batmobile

iTrader: (32)

I'll be installing stock springs so its baseline numbers are what, 292/114? Is that the actual rate you are talking about? GM rears are linear fronts and progressive rears right?

Anyway, with cut rear springs, my ride jumped back up roughly .75". Dammit! (Before with Strano's+Isolator: 27.25"; After with cut springs and HH mod: 28") I was hoping to test these springs tomorrow but it looks like I'm going to have to take 'em out, cut some more and test fit them first.

How much more should I cut off? A quarter of a coil, half?

JD_AMG

Stock LS1 springs *should* be linear.
I think what Sam is saying is make sure to get a base line number before you cut because there are many variables at play here that could skew the numbers (much like getting a baseline dyno run).
What if you actually have LT1 springs? 1LE springs? What if the springs have just worn overtime and lost rate?
Get a base line to spring rate first, then cut, then get that spring rate to verify how much rate was actually gained.

SparkyJJO

iTrader: (11)

I still can't imagine why you'd want to go to a cut stock spring from what you have. It is like going backwards...

Gonna put some decarbons back on it too?

jimmyblue

iTrader: (11)

Often, lowering springs are both shorter and higher rate.
So getting there by checkbook, or by cutting, what's the
diff?

Other than, you're figuring it out as you go, and could go
too far. And have only one degree of freedom. Where a
store-bought'n lowering spring, you can shop rate and
height independently.

But if you wanted 10% shorter and 10% stiffer, cutting
off 10% of the length would get you where you wanted
to go.

Problem being, most people don't really know what they
want.

Sam Strano

iTrader: (41)

What I'm saying is that you guys often put the numbers in stone. Like 292/114, that's an approximate number. I worked on a car that had the same front springs stock as my '01, but the rears were different (1 less coil about the same wire size, which means stiffer, i.e. *NOT* the same rate as mine). Which were 114? Maybe neither.

So I'm saying you ought to rate yours first, so you aren't assuming something from the result that isn't true.

As for the idea of getting where you want to be by checkbook or by cutting. Not so simple. A 10% increase in rate doesn't exactly cover a 10% drop in ride height. Suspensions are not linear in their actions. Generally the lower you go the more rate you need or you will end up with the bumpstops doing more of the work than the springs. Frankly there is no science to figuring that out, which makes randomly cutting stuff a bug time guess. I played with a LOT of spring rates and ride height until I settled on what worked best for me, and that's how I made my springs come to be.

02TransAm/Batmobile

iTrader: (32)

I understand what you are saying. I'm not trying to give people a concrete answer as to what one coil will change their spring rate to as there are variables at play that may skew results - it's just meant to give people a ballpark figure. I'm sure stock springs aren't 292 exactly but more like 292 +/- 5 or so. It would also be dependent on exactly where the cut was made. But if cutting a coil results in an increase to 325/130 let's say hypothetically, it's jus a rough estimate that someone could take with them since no one has ever tested cut springs that I know of and so we could use as reference instead of hypothetical formulas. I'm sure there might be some variability with your spring rates too. I thought about testing yours when I take them off but it's 30 bucks to test per spring!

Sam Strano

iTrader: (41)

I got ya... but remember this is the internet, and people tend to take what they read as gospel. Please bear that in mind, and it's for that reason it's pretty important to do a before/after test of the same springs otherwise it's not worth wasting your money because you'll get an erroneous result not knowing the baseline.

If it helps LT1 fronts were rated around 310 in front. A human can't feel anything less than about a 10% change, not really which is also something to consider.