Spring Rates at Different Lift Heights

I am currently lifted at 4"s 32" (bfgs)with a combination of OME springs and Terreflex spacers and shackles JKS CAs etc. At this lift height and the soft OME springs, the off road performance is great, but its road manners are a little sketchy/tipsy. I am thinking about replacing the front coils with either the RE 4.5 coils or the RE 3" ZJ coils in an effort to get rid of the spacers and to stiffen up the ride a little and improve the road handling. Does anybody know if the 4.5 xj coils are softer than the 3" ZJ coils, and which would you recommend. In theory the higher the lift--the stiffer the spring. Am I on the right track?? Etc. Thanks

If you're like the rest of us, you'll like the stiffest spring you can find. So far, the RE 4.5" ZJ spring has been the stiffest, but there may be some stiffer ones out there now. Many of us run that spring and it is by no means too stiff. I believe it's 225 lbs/in. You can call around to the various venders and ask them for their spring rates, and decide from that. I don't think a spring is available that would be too stiff. The shocks are what will actually determine the ride stiffness anyway.

both shocks and springs transmit force to the body during a bump impact. both will increase the harshness of the suspension if both the spring rate and the damping level are increased.

jjvande said:

both shocks and springs transmit force to the body during a bump impact. both will increase the harshness of the suspension if both the spring rate and the damping level are increased.

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I'm running the DT 3000s for shocks--from what I understand a fairly soft damping rate. Even with the soft shocks, sharp impacts are fairly brutal--more to do with CA angles I would think.

What I'm more interested in controlling is that short amount of body roll that occures right before the sway bar is loaded enough to start controlling the roll. It's a quick pitch followed by stability. Its kind of the boat feel during small directional corrections. If I get into a turn hard it is fairly stable.

Richard--what is the reasoning for wanting the highest spring rate coils? Is this more to control body roll on road or is there reasoning for off road maners-- ie. high speed off road??

FWIW, Currie has a new 4.5" "jeepspeed" coil spring that has a dual rate

it is rated

250/300


Those might be a good compromise..

The stiffer spring provides better balance! I would still like to find someone who has info on the Currie 5" springpack?

What info do you want??

those are double military wrap 11 leaf springs with 150lb rating..

the offroad race trucks seem to get soft rear and stiff front ends..

I would like to hear from someone that uses them! I still cant get my RE1462's to work(flex) as well as the front does.The 150LB springrate is just barely more than a stock springpack!

GoatMan, Rancho coils are stiffer then those. Not as tall though. As for rear leaf flex, my tomkens will stuff all the way to the stock bumpstops, droop isn't the best though. No idea what their spring rates are but they do make them in a 6" and 8" leaf.

Look into 80-96 Bronco/f150 coil springs .... Rates from 380 - 560+ :wow:

maybe a little over kill though

http://www.patricksnorton.com/bronco/lifttech.html

If you get a stiffer front coil, that will make the rear work harder and will cause to flex more.


a leaf isnt going to flex as easy as a coil, unless you run a REALLY long soft leaf, the stock length leaf will limit a bit.

You could always get a stiffer front spring and run a currie anti-rock instead of discos in the front, that combo would make the rear work more

Duane said:

I'm running the DT 3000s for shocks--from what I understand a fairly soft damping rate. Even with the soft shocks, sharp impacts are fairly brutal--more to do with CA angles I would think.

What I'm more interested in controlling is that short amount of body roll that occures right before the sway bar is loaded enough to start controlling the roll. It's a quick pitch followed by stability. Its kind of the boat feel during small directional corrections. If I get into a turn hard it is fairly stable.

Richard--what is the reasoning for wanting the highest spring rate coils? Is this more to control body roll on road or is there reasoning for off road maners-- ie. high speed off road??

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The coil springs by nature don't have a stiff ride like a leaf spring does (don't anybody get their panties in a bunch, I'm talking very generally here). One of the reasons for this is that there is no friction in the action of a coil spring. Since we lift our rigs and load them down with heavy add on equipment, a much stronger than stock coil spring is what works. No one has come out with a coil spring that is too stiff yet, which is why I said get the stiffest one you find. I don't remember what the Rancho XJ/ZJ coil is rated at, but it (like someone said) and the RE 4.5" ZJ coil have been the stiffest out there. That new Currie Jeepspeed coil looks very interesting.....maybe a new set of coils is in my future.

The ride with a Rancho coil or an RE ZJ coil is still very good, I've run both, and they add stability in all situations. Obviously, highway stability is desired, and they are better on the trail by reducing sway and bottoming out which is better for everything.....dropping off of rocks and ledges, off camber situations, and quick trips to and from the trail.

Don't know about that initial sway you are describing, could be a combination of soft springs and soft shocks. Make sure your sway bar bushings and links are tight. I've found that the stiffness of the rear springs and shocks make a huge difference in stability. I run fairly soft rear springs, and with my Rancho 9000 shocks set on anything less than 5, I'm not comfortable without my sway bar on the highway. With the 9000's set on 5 (highest setting) I'm comfortable driving without the sway bar. The stiffness of those rear shocks makes a big difference.

I broke a front shock three weeks ago in JV. The front end rides very soft and comfortably through dips and bumps without that shock there, even with a relatively stiff coil. The shock is designed to resist that quick motion more than it resists a slow motion.

Weasel said:

GoatMan, Rancho coils are stiffer then those. Not as tall though. As for rear leaf flex, my tomkens will stuff all the way to the stock bumpstops, droop isn't the best though. No idea what their spring rates are but they do make them in a 6" and 8" leaf.

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I don't remember what their rate is, do you?

Goatman said:

I don't remember what their rate is, do you?

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Richard, if you're refering to the Rancho coils, they're rated at 240 lbs/inch.

I use those and also have the ACOS, the combo is great!!

Thanks to all --great info

this thread just got me thinkin...

Early Bronco coils....

I just shot off some e-mails for some measurements and spring rates. all I could find was info on one set of coils "for heavier trucks" was 315 lb/in and they make ones "for lighter trucks" as well.

I'm hoping they hit the 240-280 lb/in mark and with unloaded length measurements, one could figure out a lift amount. something around there, to me would really be the hot setup. I run rancho coils, and I'd actually like something a little bit stiffer.

the place I e-mailed also sells the EB coil buckets and retainers, and needless to say, its a MUCH beefier piece than what you'd find on the XJ (and it's probably what I'll use on my axles when they go under the XJ)

there's gotta be SOMETHING out there I can run that'll give me about 5"-6" lift, w/ a 280 or so lb/in rate without having to run spacers. not to mention, the EB coils are pretty darn cheap too... and I like that

Duane said:

In theory the higher the lift--the stiffer the spring. Am I on the right track?? Etc. Thanks

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I'm not sure if you mean that springs are stiffer because they are taller, or if you mean you want a stiffer spring with a lifted suspension. If the former -- that's not correct. Spring rate (coils) is a function of coil diameter, wire diameter, and number of coils.

I disagree with Goatman on two points. First, some springs are too stiff -- case in point, the 4" Trailmaster coils in my MJ.

Second, I don't know why Goatman posted a roll eyes emoticon to jjvande's statement, because what jjvande posted is exactly correct. What I've found works best (for me, anyway) over some 40+ years and about a million and a half miles of driving is that soft springs require a firmer shock with more "jounce" resistance, while stiff springs ride best with a softer shock that's proportioned for more "rebound" resistance. (Of course, it's virtually impossible to get a shock manufacturer to tell you how any of their shocks are calibrated.)

I vaguely recall reading that the stock XJ spring rate (front) is around 160 lb/in. and the Up Country is around 200. If you have a heavy winch bumper a spring around 220 to 240 would probably be about right, w/o the weight of a winch I would not go stiffer than 220. All else being equal, you get more articulation from a softer spring that has more coils to reach the same height.

If your concern is keeping it flat on pavement, try a stiffer anyt-sway bar. Jeep used three or four different diameter bars, the biggest being the 28mm used in the 6-cyl Wagoneer models. If you can't find one of those, Addco offers a 1-1/8" (28.6mm) replacement, available from Quadratec. They also offer a stiffer than stock rear sway bar.

Eagle said:

I disagree with Goatman on two points. First, some springs are too stiff -- case in point, the 4" Trailmaster coils in my MJ.

Second, I don't know why Goatman posted a roll eyes emoticon to jjvande's statement, because what jjvande posted is exactly correct. What I've found works best (for me, anyway) over some 40+ years and about a million and a half miles of driving is that soft springs require a firmer shock with more "jounce" resistance, while stiff springs ride best with a softer shock that's proportioned for more "rebound" resistance. (Of course, it's virtually impossible to get a shock manufacturer to tell you how any of their shocks are calibrated.)

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How much lift on that MJ, Eagle, and have you tested various shocks to see how stiff the springs really are? Do you know it's the springs or could it be the shocks? The question is about a lifted XJ and he is uncomfortable with the amount of sway that he is experincing. I know that there are exceptions to every rule, but nearly all of us that have run a variety of coils on lifted XJ's prefer a stiffer spring. Those of us who have run the stiffest springs out there (other than the brand new Currie) don't think that they are too stiff, and could go stiffer. So based on the question and our collective experience, I said he couldn't go too stiff with what is available.

As far as my rolled eyes, the response is way to general. Sure you can have way to stiff of a spring, but like I have said, they aren't available for the front of an XJ. It's also much more difficult to get too stiff of a spring with a coil......when it relates to ride harshness from sudden impacts like dips and holes. With a coil spring, it is the shock that determines ride harshness, unless you have WAY too stiff a coil, which we don't have on the front of XJ's. Again, I'm talkking about a lifted Xj that is used off road.

We all are correct for any given situation. I believe I am pretty close on the subject matter of this thread.

regardless of who is right...

The shocks are what will actually determine the ride stiffness anyway.

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my opinion is that if sway is the subject...we should present all aspects, negative or positive, of increasing spring rate.

I run rancho 4.5" in the front and rustys 4.5" in the rear. This combination is working well for me. but i too want more stability. I think that a bigger anti-sway bar may be the way to go too.

anyone running the anti-rock, what do you think?
thanks

-J