Hey guys,

I would like your opinion on the arch/flatness of my rear leaf springs. I felt the rear suspension has gotten significantly stiffer over the past 5 years and these images may show why as the leaves are getting pretty flat and increasing the effective spring rate. What do you think?

The following images are with the jeep unloaded and the axle tube set at ride height (images with no tire).

Setup (installed 5 years ago):

OME CS033RB leaf springs
JKS shackles
LII shackle relocation brackets
shackle angle roughly 45 degrees

 

A flatter spring gives you a softer suspension.....not stiffer.

What's easier to bend both ways .....a straight pipe, or a pre-bent pipe ?

A flat spring takes little to make the axle move up....a curved spring takes a lot more, as not only do you have to move the axle weight, you have to flatten the curved spring out some.....

That's why the higher the arch on a leaf spring, the stiffer the ride, and why many go to a longer spring to get a flatter spring for the same lift.

and @ 5 yrs, I'd say the shocks are also suspect, as well as bushings, and maybe even your memory of how well it did or didn't ride.


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Aren't we discussing different concepts? You were considering two different springs with the same load (one maintaining its arch due to its higher effective spring rate and one loosing some of its arch due to its lower effective spring rate). I was considering one spring, but at two different points in its travel, where the effective spring rate increases as the leaf flattens out.

As for 5 years, I certainly agree with you about all of those other components, including my memory!

 

I'd love to have some nice springs like that.

Not sure I dig the shackle angle or shackle. I'd probly drill a set of holes in between and try and straighten it some.

that look lilooa good riding leaf pack your definitely not binding at th he shackles

 

Spring rate is how much force it takes to deflect or bend the spring....a flat spring will always have a lower spring rate than an arched one as long as everything else is equal (leaf count, leaf thickness, material, etc).

Your's have lost their spring (or ability to maintain shape) and that is why they have flattened out....meaning the spring is now weaker and less able to defy any force trying to move them



That shackle angle is way better than stock....you want it at an angle, not straight up and down


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Yep. They are shot.






Why? Educate us, please!

 

Well, for another opinion. What you have appears to be a two stage spring, in other words a flat leaf at the bottom. Some people call them overloads, not their proper name. At any rate, your arched leaves have lost some of their arch over time, a common problem with leaves with a low rate that flex a lot. I think you are right that the ride has gotten stiffer over time since you are now fully engaged with the second stage. What you are willing to do depends on your budget.

 

Shackle may actually be at such a ange the that spring feels stiffer.
that is a long shackle maybe it's at 45 either way whatever angle its at I think I'd straightn it some to me means drilling in between. well maybe not run it in the next hole see what the suspension does worse better cant tell.
I dunno, I think this a free adjustment if there are no labor exspenses envolved. I'd surely hope there aren't

 

if the shackle is vertical then when you hit a pothole/bump, the leaf has to flex before anything happens.....and that requires a lot of energy which results in really feeling the impact

if the angle is like in the pics, when you hit a pothole/bump, the shackle will move before the leaf move....so some energy is absorbed by the shackle moving before the leaf flexes, so the felt impact is not as harsh

If you need droop, and the shackle angle is vertical, then the shackle can only swing forward a few degrees (maybe 1") before it is limited and the rest of the droop must come from flexing the leaf spring............on a 45 deg shackle angle, during droop, the shackle can swing forward 45+ deg ( probably 4-5"), giving you a lot more droop (1" vs 4-5") before the leaf spring is fully maxed out.


That's why the shackle angle relocation kits (and there is one being used in the pics) are so popular....to get away from a more vertical shackle angle to more of a 45 deg angle and obtain a softer ride


Not really a different opinion......but your info extends past what I was getting at....what I said is true, up until the point that you are riding on the 'overloads' or 2nd stage all the time, then what you said definitely comes into play. The spring rate would be softer, until the flex is enough to let the spring go into a negative arch and engage the bottom overland or 2nd stage spring.

I'd not think he is there just yet from the pics, as he has a shackle relocation kit on it. If he had the stock almost vertical shackle angle, yeah, I'd say he was.

You could try removing the very bottom leaf and see how that rides to maybe buy you some time before you have the buy new leafs.


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Thanks guys, I appreciate the insight.


Any options I am not considering in this list below?
1. add-a-leaf
2. new off-the-shelf leaf packs (lots of options)
3. new custom leak packs (given vehicle weight, max payload, etc.)
4. rear coil spring conversion

I found this video helpful to see the motion of the shackle and how the force required to compress the spring changes.

https://www.youtube.com/watch?v=BhqZkF2D6ss​​​​​​​

 

Coils will always ride better, given the same spring rate. The reason for that is that leaf springs have built in friction when the leaves move along a compressing or decompressing leave above them. The cheap option is to use an add a leaf with more free arch than the XJ and retain your bottom leaf. The popular option is to use Chevy S10 springs. If you add a leaf, subtract one of the original leaves of same length. Another one, not so popular is the Isuzu Rodeo rear spring. Lots of arch in them and the leaves are more the thickness of an XJ. If you go this route the idea is to keep the spring rate the same as original but increase the free arch of the spring with a load on it

 

Also, if you go the add-a-leaf route, bear in mind

1) they will feel stiffer

2) they will over time do the same thing...sag

3) you will probably need to move move your shackle upper mounting point

 

Lessening the shackle angle is free and easy t try. Dont make it straight up and down but just lesson it some.
see if ride gets better or worse it will certainly change in same way by changing the angle.

Cut the over load portion off the leaf. Shorten it.
Theres I guess few free things to try.

 

Maybe I didn't communicate very well. If he substitutes a higher arched leaf or leaves instead of just adding, then his spring rate will remain about the same. I currently run a very soft rear spring that is a bastard pack with the same number of leaves, plus an inverted second stage. Doesn't carry a load well, but sure rides nice and wheels great. I think the term add a leaf always conjures an image of adding one more leaf. Again this is a substitution with the same number of leaves when completed

 

Yeah, I thought you meant an add-a-leaf like in place of a spring pack....the 1 big hard arched spring you insert to get a stock spring lift...