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

[Matt]

My OME springs came in yesterday and now I see where the issues are in the calcs.

The free height spec is correct, but as I though, the 8.9 coils includes the closed & ground end which is not considered part of the "active coils" for the estimates. It also throws off the adjusted free height estimate a bit. Another issue I found is that the top coil is actually closed as well (last coil flattended). Cutting this section off doesn't change the spring rate much.

With 1/2 coil cut off i'll be ~14.25" free height
With 3/4 coil cut off i'll be ~13.75" free height
With 1 coil cut off i'll be ~13.38" free height

I think i have an idea...need to go measure my XK again

[Matt]

CLIFF NOTES: If i cut 1/2 coil off the MD spring and set the 5100s to the highest setting, I think i'll end up .25-.8" higher than I currently sit (depends on the final spring rate). So i'm going to do that first since I can always cut more off or drop the 5100s down to a lower setting if its too high.

Cutting off half coil basically gives me the same free height as the OME HD, but with a lower spring rate. Assuming the spring rate doesn't change (to be conservative) The cut spring will reach equilibrium at about 10.6" which is about .65" more compression and approx 1.3" lower ride height. Add in the lost 1/2" from also removing my strut spacer and I'd be 1.8" lower than my current setup.

Add in the ~2" from the 5100s and i'm looking at ending up about .25" higher than I am now. And that's being conservative.

If I assume the last half coil is active that would result in a new spring rate of ~570 lbf/in for a compressed height of 10.9" resulting in ~.7 lower ride height. Plus the extra 1/2" from spacer and i'm looking at 1.2" to make up with the 5100s. So i could end up with about .8" more lift than i currently have (too much). If that happens, I can always drop the 5100s to the middle setting or cut more off the spring.

[06JeepXKHEMI]

Matt, when are doing this?!? I think Im finally catching on to this hahaha

[Matt]

If my struts and UCA's show up today.... maybe tonight/tomorrow. I'd like to get it done this weekend so I can let everything settle and then adjust them if I need to while im off during the holidays. And my bumper will be here next week so i'd prefer to have some free time to do that too!

[06JeepXKHEMI]

Big things happening!! I like it

[paroxysym]

matt, i was looking through johns 1" lift thread and he has the following spring rates listed for OEM coils:

- Hemi XK 601lbs
- CRD 473lbs (d), 433lb (p)

[Matt]

I wonder where he got that # from. That seems a bit high based on how much stronger the OME HD springs felt compared to my stock ones.

I always assumed that the stock rate was lower, even if just slightly, than the MD springs. ... I guess ill find out soon enough :/

[jjt250]

Hey guys, I got that number from Diesel Power Mag's build of their 2008 Jeep Grand Cherokee. I'm not sure how accurate those numbers are or how they got that information. Here's a link: http://www.dieselpowermag.com/tech/g.../photo_09.html

[Matt]

Awesome man thanks for the link. lol but damnit I hope that's wrong, i didn't want a weaker spring than stock

Maybe it's a typo and they meant 501 [wishful thinking]. I forget what the weights are, but I didn't think a Hemi XK was all that much more than a CRD WK to warrant 130-170lb more spring rate. I guess it's possible though.

[jjt250]

You could be right about a typo, Matt. The CRD weighs a little more than a Hemi and I don't really see why the XK would weigh that much more than a WK in the front. All I can tell you is that there definitely was a noticeable difference (just by eyeing them) when I compared the two springs side by side. Ride is a little stiffer and gave me probably +1/4" of lift. So over 130lb stiffer spring rate? I'm not so sure. I never got around to it, but I still have my stock CRD springs laying around if you need me to take some pics and measurements. Not sure how much that'd help you, but just let me know what you need and I'd be happy to help!