Here is the formula for calculating spring rate for leaf springs...
Leaf Spring Rate = (WN/12) x (1000T/L)^3
W = Width of Leaves (in)
N = Number Of Leaves
T = Thickness of 1 Leaf (in)
L = Length of Spring (in)
12 = Constant for Leaf Springs
Based on that formula, your values are as follows:
Front Spring rate: = 1242 Lbs/in
Rear Spring rate: = 967 Lbs/in
These calculations are approximate, as they do not measure the unloaded length (no weight on the spring), and I suspect that since your springs are so heavily arched they somewhat invalidate the formula which is designed for more conservative arch numbers.
If you were to pull one of the longer leafs, you'd soften it up by roughly 100 Lbs/in for each leaf you removed...but as you can see, they are going to be REALLY stiff no matter what.
For comparison, a spring that is considered "good flexing" would be less than 400 Lbs/in....there are some aftermarket springs that even go below 300 Lbs/in.
The challenge is to going to be understanding how much sprung weight your truck has (the weight of the frame and engine and cab). That is what is pushing down on those springs currently. When you start to actually flex this truck, you will be taking weight from one side of the truck and adding that pressure to the side that is articulating. For the sake of arguement, let's say that your sprung weight is 3000 Lbs, and you have a weight distribution of 50/50 (1500 Lbs front/1500 Lbs rear). That means that you have 750 Lbs over each of the front springs when the vehicle is at rest. When the suspension articulates, you move that weight from the wheel that is not climbing, to the one that is. Theoretically, if you had one front tire just barely dangling off the ground, the other tire would be carrying all 1500 Lbs of front sprung weight as it climbed the rock.
What does this all mean?
A spring rate of 1242 Lbs/in means that the spring will compress 1" for every 1242 Lbs applied to it from above.
In the case of those calculations, if you were to fully load one side of your suspension (like in the example above) the spring would only compress about 1.25"..... and that's about the MOST it will ever change, unless maybe you were jumping it through the air!
Based on that information, your shackles will only need to be long enough to accomodate an inch or two of movement from the spring as it flattens. It certainly doesn't seem like you'll need to add much length (if any) to the existing shackles...all you'll need to do is optimize the angle, so that they are laid-back correctly.
Leaf Spring Rate = (WN/12) x (1000T/L)^3
W = Width of Leaves (in)
N = Number Of Leaves
T = Thickness of 1 Leaf (in)
L = Length of Spring (in)
12 = Constant for Leaf Springs
Based on that formula, your values are as follows:
Front Spring rate: = 1242 Lbs/in
Rear Spring rate: = 967 Lbs/in
These calculations are approximate, as they do not measure the unloaded length (no weight on the spring), and I suspect that since your springs are so heavily arched they somewhat invalidate the formula which is designed for more conservative arch numbers.
If you were to pull one of the longer leafs, you'd soften it up by roughly 100 Lbs/in for each leaf you removed...but as you can see, they are going to be REALLY stiff no matter what.
For comparison, a spring that is considered "good flexing" would be less than 400 Lbs/in....there are some aftermarket springs that even go below 300 Lbs/in.
The challenge is to going to be understanding how much sprung weight your truck has (the weight of the frame and engine and cab). That is what is pushing down on those springs currently. When you start to actually flex this truck, you will be taking weight from one side of the truck and adding that pressure to the side that is articulating. For the sake of arguement, let's say that your sprung weight is 3000 Lbs, and you have a weight distribution of 50/50 (1500 Lbs front/1500 Lbs rear). That means that you have 750 Lbs over each of the front springs when the vehicle is at rest. When the suspension articulates, you move that weight from the wheel that is not climbing, to the one that is. Theoretically, if you had one front tire just barely dangling off the ground, the other tire would be carrying all 1500 Lbs of front sprung weight as it climbed the rock.
What does this all mean?
A spring rate of 1242 Lbs/in means that the spring will compress 1" for every 1242 Lbs applied to it from above.
In the case of those calculations, if you were to fully load one side of your suspension (like in the example above) the spring would only compress about 1.25"..... and that's about the MOST it will ever change, unless maybe you were jumping it through the air!
Based on that information, your shackles will only need to be long enough to accomodate an inch or two of movement from the spring as it flattens. It certainly doesn't seem like you'll need to add much length (if any) to the existing shackles...all you'll need to do is optimize the angle, so that they are laid-back correctly.
Just a thought...
Its 27" of lift
