New IRO 4.5" Spring Pack + Add-a-Leaf?

[VAhasnoWAVES]

All springs are progressive, it's just whether they have a "linear" rate or more of a "geometric" rate

i think i know what you are trying to say... but terminology is important, and this statement is in fact, wrong.

a linear spring rate implies 1" of displacement for ever X amount of weight. which does not produce the same curve as a progressive spring.

 

[maxbraketorque]

I've seen people and companies state that leaf spring packs are progressive (I believe that Deaver is one of the companies that told me this), but the formulas for leaf spring pack spring rate indicate that it should be a straight rate. Kind of puzzling. But for sure, shackle movement produces a non-straight rate. Assuming the shackle is either straight up or kicked reward, then as the shackle-end travels upward during spring compression, the effective spring rate becomes digressive until the spring goes flat. When the spring goes into negative arch, the shackle will start traveling back downward, and the effective rate will become progressive. Anyhow, kind of OT.

 

[VAhasnoWAVES]

ehhh... the spring is acting on the lever arm (shackle), not the other way around. remove the shackle and add a slider, the spring is still operating the same. any measurable difference will be so small that the average "butt dyno" isnt going to notice.

side note... if your springs are inverting they are being pushed passed their working limit and will fail in a short amount of time.

 

[NOTNSUV]

Fill slots with grease or just install as is? They go in very easy.

Sent from my Pixel 4a using Tapatalk

 

[RCP Phx]

Definitely load it up with grease before assembly, you've got the greaseable bolts but have you drilled the sleeves?

 

[RCP Phx]

Also make sure there is a little gap(usually about 1/8") between the bushings so grease can flow.

 

[NOTNSUV]

Also make sure there is a little gap(usually about 1/8") between the bushings so grease can flow.

Not sure about making a gap. The 2 pieces bump together when flush on the spring.

Good point on drilling the sleeve but t might be a real challenge with grade 8 sleeves and no flat surface to drill. Also, I'm thinking grease would just squeeze out the ends of the sleeves before it made its way through a tiny hole to the bushing - path of least resistance. I'll probably pass on that and settle for the bolt to sleeve surface being lube-able. I have an excellent grease I'll be using that doesn't water wash so I expect it will stay put in the bushing and sleeve and give good results.

http://powerupusa.net/index.php/products/power-up-products/thixogrease

Delivery of the wayward spring pack is scheduled for this afternoon. Fingers crossed.

Thanks.

 

[RCP Phx]

i think i know what you are trying to say... but terminology is important, and this statement is in fact, wrong.

a linear spring rate implies 1" of displacement for ever X amount of weight. which does not produce the same curve as a progressive spring.

I know I probably didn't choose all the correct terms but it's why manufacturer's don't always give spring rates (at what height)?

Not sure about making a gap. The 2 pieces bump together when flush on the spring.
Good point on drilling the sleeve. Might be a challenge with grade 8 sleeves.

I've cut additional grooves (inside to outside) under those circumstances. The sleeves should drill with no problems.

 

[RCP Phx]

I've cut additional grooves (inside to outside) under those circumstances.

I was thinking about a different application, but in your case you can add a chamfer on the inside face of the bushings.

 

[VAhasnoWAVES]

I know I probably didn't choose all the correct terms but it's why manufacturer's don't always give spring rates (at what height)?

i dont know if that is a question or a statement... but...

a few reasons come to mind quickly.

1 - spring rate is only half the equation, free length is the other. two springs with the same rate can have very different free lengths. two springs with the same free length can have very different rates.
2 - tolerance on spring rates are actually very loose. i remember working with AFCO for shock tuning in college when building our race buggy. our calculations said we wanted a 92.5lb spring (just an example number), and their rebuttal was that their manufacturing process wasnt refined enough to be that accurate and to pick an 80or 100lb spring (again, arbitrary numbers) off the shelf. so someone could easily load up a spring with the advertise poundage (spring rate being in inch/lb), measure the displacement, and claim false advertising.
3 - and of course... if the general public likes your spring, dont give away your secret to competition for free. not that buying a pair of springs and putting them in a spring tester is difficult.







re-arching the leafs for more lift is another option (basically making a higher lift spring) if the OP wants more height when loaded rather than adding another leaf and changing the rate like you said early on.

 

[maxbraketorque]

ehhh... the spring is acting on the lever arm (shackle), not the other way around. remove the shackle and add a slider, the spring is still operating the same. any measurable difference will be so small that the average "butt dyno" isnt going to notice.

side note... if your springs are inverting they are being pushed passed their working limit and will fail in a short amount of time.

I imagine that you've seen or worked through the analyses of how shackle movement affects wheel rate. A shackle that is tilted back will produce minor leaf spring straightening forces that have a very minor effect on spring rate, but vertical movement of the shackle-end has a substantial effect on wheel rate if the shackle is sufficiently long and sufficiently tilted back. In this regard, a shackle has a much different effect than a slider. Presumably you were referring to the minor effect of the shackle pulling on the spring (which is a real force when the weight of the vehicle is on the shackle). I agree that's a no-nevermind effect.

As far as inversion being bad, my impression is that its more about the total movement (flex) of the leaf rather than specifically about inversion. It looks to me that stock XJ leaf springs are close to flat at ride height and do invert as part of normal rear wheel travel. There is no other way for the stock bump stocks to ever touch the axle.

More OT-ness...

 

[NOTNSUV]

From my original post I misspoke. The new leaf springs are IRO 3.5". I kept thinking 4.5" which is close to what they'd be with AAL.

FWIW the shims in the old springs are 4* and gave me a pinion angle of 2.5*. They'll be going in the new springs.

 

[75SV1]

From my original post I misspoke. The new leaf springs are IRO 3.5". I kept thinking 4.5" which is close to what they'd be with AAL.

FWIW the shims in the old springs are 4* and gave me a pinion angle of 2.5*. They'll be going in the new springs.

I thought IRO had an AAL specifically for their 3.5 rear leaf springs, that would bring it up to roughly 4.5" .

 

[75SV1]

From my original post I misspoke. The new leaf springs are IRO 3.5". I kept thinking 4.5" which is close to what they'd be with AAL.

FWIW the shims in the old springs are 4* and gave me a pinion angle of 2.5*. They'll be going in the new springs.

I thought IRO had an AAL specifically for their 3.5 rear leaf springs, that would bring it up to roughly 4.5" .
https://www.ironrockoffroad.com/product/xj-35-leaf-springs.html

 

[RCP Phx]

These AAL are from IRO and an option with the leaf pack that fit between 3rd and 4th leaf making it 8 instead of 7. Not just a stub added to the bottom of the pack or such.
That seems like a full/complete pack with an extra leaf rather than piecemeal AAL, no?

https://www.ironrockoffroad.com/product/iro-spring-add-a-leaf.html

Please elaborate.

I thought IRO had an AAL specifically for their 3.5 rear leaf springs, that would bring it up to roughly 4.5" .

I thought IRO had an AAL specifically for their 3.5 rear leaf springs, that would bring it up to roughly 4.5" .
https://www.ironrockoffroad.com/product/xj-35-leaf-springs.html

 

[NOTNSUV]

I thought IRO had an AAL specifically for their 3.5 rear leaf springs, that would bring it up to roughly 4.5" .
https://www.ironrockoffroad.com/product/xj-35-leaf-springs.html

That's correct, except it becomes the 3rd leaf, so between 2nd and 3rd. And they tell me on the phone it adds 1 - 1.5". Just about have them installed w/o the AAL, but with required 'lift' shackles. I'll see what it nets for lift and how it rides and handles my load. Then if not up to expectations I'll AAL or to get to 4.5", install a lift SRB that I have in hand - or if my shackle angle ends up ugly with the standard pack. If the lift is right but poor shackle angle then it's Stinky Fab SRB time.

Question is whether the AAL will kill the ride, but that will be a subjective, seat-of-the-pants answer. My initial rationale for this change is the existing springs felt soft with the load I use - and I'm wanting CAD up front where the minimum lift is 4.5" according to conventional wisdom (and manufacturers).
Paralysis by Analysis. I turn this stuff into a saga.

IRO has been very good on the phone but the fact I had to call them a few times for clarification begs a set of instructions with the leaf packs and the AAL. Not everyone has done this before. But I have it figured out and borrowed a killer set of c-clamps for the job. Had to have those just to install the shims for pinion angle adjustment.

Hopefully will have it on the street this evening. If that goes ok, I'll head for the dirt with a full load.

 

[NOTNSUV]

Ok, next question:

Why would the AAL on the 7-leaf pack IRO to get to 4.5" (8 leafs total) ride differently than say a 4.5" spring from RC, RE, etc, etc? Simply due to more leafs?

This AAL is not a bastard pack off an S10 or such but is engineered to match the IRO spring pack arch and becomes 3rd longest in the pack.

Thankya.

 

[RCP Phx]

It's just that usually folks seek a pack that's built specifically for a height they want, anything else is a crap-shoot!

 

[RCP Phx]

Look at it a different way! If you had a spring (regardless of height) and you were extremely happy with ride, a AAL will change that to a much firmer ride and add height.

 

[maxbraketorque]

Ok, next question:

Why would the AAL on the 7-leaf pack IRO to get to 4.5" (8 leafs total) ride differently than say a 4.5" spring from RC, RE, etc, etc? Simply due to more leafs?

This AAL is not a bastard pack off an S10 or such but is engineered to match the IRO spring pack arch and becomes 3rd longest in the pack.

Thankya.

It all depends on spring rate and shackle angle. There's not much that can be done for shackle angle when working with the stock shackle mounting point, but for sure the spring rate of a leaf pack can be whatever the manufacturer wants. In my research on XJ leaf springs, I found that nearly all manufacturers aimed for a stiffer-than-stock spring. Here is the info I gathered on 3.5-4.5" lift springs:

- RC: quoted to be 186 lbs/in, but I measured the spring rate to be 230 lbs/in with it on my XJ. The shackle angle was vertical, so my measurement should be representative of the true spring rate of the spring.
- Rusty's: quoted to be 230 lbs/in.
- BDS: quoted to be 230 lbs/in.
- RE: quoted to be 190 lbs/in.
- OME CS034RA and CS034RB both quoted to be 148 lbs/in which is very close to stock.
- IRO: quoted to be 185 lbs/in, 215 lbs/in with AAL.