Custom spring & 5100 adjustable strut combo (1.5-3.5 lift range)

[paroxysym]

the more i thought about this, the more im intrigued by your findings..

im trying to see what to match the OEM hemi coils up front with in the rear- when i throw them in the front with the 5100s adjusted to 2".

[Matt]

I've been racking my brain about how to decide how much i want to cut off.... I can always cut more off (or drop down a setting) but I'd prefer to get it right the first time

To cut out the variables with the stock springs, I'm taking a new approach and basing my "target height" from where I sit right now with OME HD springs/struts.

My front is currently 22" hub-to-fender with OME HD springs, OME struts and 1/4" strut spacers.

OME HD springs are 14.37" extended and have a rate of 630 lbf/in. I measured the spring at static ride height and its right at 11.25"; which means each strut has approximately 1965 lbf.

EDIT: I forgot to factor in the 2:1 lift ratio in my original post

Using that load, the following OME MD springs would produce less lift as shown:

OME MD uncut = 14.56" free height w/530 lbf/in rate = 10.85" @ equilibrium = .40" less = .80" lower
OME MD .5 cut = 13.74" free height w/560 lbf/in rate = 10.23" @ equilibrium = 1.02" less = 2.04" lower
OME MD .75 cut = 13.33" free height w/580 lbf/in rate = 9.94" @ equilibrium = 1.31" less = 2.62" lower

That's not taking into account the 1/2" lift i'll be losing from removing the strut spacer as well. Adding that I get:

OME MD uncut = 1.3" lower
OME MD .5 cut = 2.54" lower
OME MD .75 cut = 3.12" lower


Soooo, I think i've convinced myself that cutting one complete coil off is a bad idea to start with.

I feel like i'm missing something... gonna have to chew on this one a bit more or maybe just start with an un-cut spring and see where I end up.

[Matt]

Just for giggles....

OME HD 14.37" free height, 8.9 coils, 630 lbf/in
HD 1/2 coil cut = 13.56" w/667 lbf/in = 10.61" = .64" less = 1.28" lower (1.78" lower w/spacer removed)
HD 1 coil cut = 12.75" w/710 lbf/in = 9.98" = 1.27" less = 2.54" lower

I feel like these figures are over-estimated... likely due to the difference between "coils" and "active coils" which does factor into the calculations (I've been assuming they're all active coils); let alone all the other guestimates i've been working with. I'm thinking the "free height" might also be measured from the center of the wire, not from the edges of the spring.... that'd definitely throw these figures off.

Case in point there are guys running a modified superlift with 1 coil cut off an HD spring. Using these assumptions/estimates cutting that one coil would nearly negate the initial lift achieved by that spring.

[06JeepXKHEMI]

Matt, your genius talk confuses the **** out of me... That being said, why cut a coil at all with the HD springs at the lowest setting on shock?

Sent from my SGH-T999 using Tapatalk

[Matt]

That being said, why cut a coil at all with the HD springs at the lowest setting on shock?

Because I want to run these on the lowest setting when i install the Superlift.

The goal is to have an adjustable strut setup that nets ~3" lift on the highest setting and then can be adjusted down to ~1-1.5" when you install the superlift for a ~5.5" lift.

If I just put the 5100s on the lowest setting and use HD springs, I won't have the ability to adjust them down at all. And when I go with the superlift i'd like to have a stiffer spring than stock, which is achieved by a cut OME MD spring.

..... and don't worry dude, I confuse the $(&% out of myself daily

[Matt]

I think im gonna have to stop driving myself crazy and try taking a more qualitative approach..... then cut some damn springs and install them and see what happens

OME MD = 14.56" free height
OE Spring= 13.25" free height (1.31" less than OME)

Cut OME MD spring rate > OME MD spring rate (530) > stock spring rate ... so regardless of what it ends up being, its a heavier rate than stock.

I'll double check the measurements when I have the springs here, but if 1/2 coil cut off the OME MD gives a 13.75" free height, that's 1/2" over stock which should yield ~3" lift with the 5100s on the highest setting, not including additional lift from the increased spring rate.

So there it is, i've convinced myself to cut 1/2 coil again. Lets see if it sticks this time lol

[07JeepXK]

Why not just install the OME MD springs on the Biltein struts without cutting a coil? See where that gets you and then go from there. Because once you start cutting you can't go back. If it's not what your looking for take it apart and then cut the coil and/or make adjustments to the strut as needed.

I just want to know how I can get about 1/2 inch more lift then I currently have. My OME struts are shot so those will need to be replaced right from the start. And I almost wouldn't mind a hair less spring rate than the OME HD springs.

[Matt]

Yeah Adam thats kind of what im torn with doing. My gut tells me that the uncut spring + 5100s @2" is going to be way too much. But you can always cut more off.

Though as long as my cut OME spring is taller than my stock spring I should get more than 2". If its 1/2" taller and has a higher spring rate I think ill easily be in the 3" lift range.

Either way once ive played with it you'll know what to order

[06JeepXKHEMI]

I guess this all makes a little more sense, but your math situation is way to intense for me hahaha.. I was trying to comprehend how cutting a spring would still yield lift, yes I know a stiffer spring will net more lift, hence the advertised 2" OME HD actually gives you closer to 3". By cutting the spring it increases spring rate which will negate the amount of lift??? Am I getting there Matt??? hahaha I feel like Im in school, but a fun school

[Matt]

Lol you're almost there man...

Cutting a spring increases the spring rate, but decreases spring height. The loss in lift is a result of the loss in spring height which has a much larger effect than the lift from increased spring rate.

So basically all im doing is calculating the final spring height for a given load. Comparing the final equilibrium spring heights is an indication of how much ill lose/gain from my current setup. But somethings not adding up so I think the free heights ive calculated for the cut springs are wrong (ill verify when my new springs get here)

You can pretty much ignore all my numbers. Im really posting them all more for the sake of documentation so I can come back here and read what ive done.