Rear spring install, what did i do wrong?

[ENafziger]

I have a spreadsheet I created awhile back that calculates deflection, spring rates, etc for semi-elliptical leaf springs.

Just for fun, I ran some figures.

Consider a rear leaf spring pack with 8 leaves, each 3/8" thick and 2. 5" wide, with one leaf extending all the way to the end, with the stock dodge length from eye-to-eye. The thickness in the middle where it sits on the axle is 3". The effective spring rate at static, assuming a vertical shackle, is 647. 4 lb/in. A stock truck regular cab truck would compress this pack 1. 26" just sitting static. With 2500 lbs in the bed, the total compression would be 2. 65".

Now consider a leaf pack, identical to the first, except there are 12 leaves, each 1/4" thick, with 2 leaves extending to the end. The leaf pack is still 3" thick in the center... the exact same as above. However, the spring rate is now 293. 4 lb/in, and the static unloaded deflection is 2. 78". With 2500 lbs in the bed, this pack would be compressed a total of 6. 19".

Quite a difference.

--Eric

 

[JKreiss]

Thanks for the info, that's quite impressive. I really should have done my homework before ordering them. Oh well, it's what I've got for now. I cleaned up the mounts and drove it around for a minute last night and obviously better, felt more like floating rather than jarring. I'm taking it to work this morning so i'll get a better idea of the ride now that the springs aren't bound up.

 

[ENafziger]

Thanks for the info, that's quite impressive. I really should have done my homework before ordering them.

Don't feel bad... I did my homework (or so I thought), and still ordered them!

I hope they work out better for you. My initial feeling though, is that with a 4" greater arched spring, your stock shackles are going to significantly limit travel.

--Eric

 

[pwerwagn]

Before I did the "monster rear" on my 74 (when it had the same 52" leaf's you are using, although it looks like Alcan gave you ~56's), I had some pretty heavy arched leafs made to give me lift with no blocks. I had to grind the bracket, mine rubbed just like yours are. I ground quite a bit of material, and that truck got offroaded HARD and that bracket never failed. I also towed a bit with it. I eventually went with a 2" longer shackle in tension, helped ride a bit and lowered the rear ~1". I only kept that setup a week or so, then just moved onto the 63" rears with the ORE/Shaggys Monster setup.

And yes, your shackle angle is WRONG. A tension shackle like that needs to be either vertical, or if possible at all, slightly forward at static ride height. Its nearly impossible to actually get it to be slightly forward, because the angle will force the spring to take a longer length basically and the shackle will migrate to vertical anyhow. But in theory... slightly forward based on measurements is a good goal.

And as Eric said, go check out Jungle's parts on Ramcharger Central. Also, look up the shaggys monster rear setup on Offroad Exchange.

Maybe I missed it... but what fronts did you go with? Im building a 1st gen (ramcharger) and was going to go alcans up front. I rode in one the other day and wasnt very impressed (had pos pro comp shocks too, however). I am leaning 75% towards doing the 52" spring swap up front now.

 

[DEdds]

we did this with skyjacker springs and the shackle almost leaned forward. We never had that problem. I think that alcan made the springs too long.

 

[JKreiss]

Just for a quick update... I ground down the rear hangers just to eliminate the binding, obviosly it's much better but i think there's A LOT of room for improvement. I was really impressed with Jungle's stuff but i'm scared off by the 4 3/4" of lift with stock springs. Mine look like "U" already so i can only imagine how much taller it'd sit using his kit. I'm going to work on a package (full write up on what i have plus pics) and send it to him to see what he suggests. I REALLY don't want to have to change springs again, i'll just wear a kidney belt for 200k miles until these ones wear out. I've got too many irons in the fire right now to go through ordering new springs and then figuring out what to do with the ones i already have. I already gave away the stock ones so i'm trying to work with what i've got. I'm hoping he's already got something made up that can correct the angle withoug sacrificing ride height. I'll update what i find out. Thanks guys for the direction.