Running 57" rear leafs up front

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SYRacing
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Joined: Tue Jan 10, 2017 11:20 am

Running 57" rear leafs up front

Postby SYRacing » Fri Feb 17, 2017 6:33 am

What are you guys doing to ditch the wimpy 47" springs?

Looking at the leaf spring chart it looks like the 131" WB FSJ rear springs would be a good setup up front.

Relocation of the rear hanger and possible retention of the stock front hanger with longer shackles to get the angle where it needs to be?

I have old 6" BJs lift setup SOA on my J20, the front springs are whopped out (flat) looking for longer leafs to give better life, ride and flex.

Measurements:

Stock FSJ front 22.5 x 24.5 = 47"

131" WB FSJ rear 25.250 x 31.75 = 57"

The 31.75 end would go to the relocated rear hanger.

Old pic before the front springs faded
Image

rocklaurence
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Re: Running 57" rear leafs up front

Postby rocklaurence » Fri Feb 17, 2017 9:35 am

If I were to invest in the work to add the springs, I would also do a Shackle Reversal. Plus, only run enough shackle to allow expanssion of the spring and adjust Caster with a wedge at the spring. Next, with all that droop-you'll need to address the front drive shaft [steep angles, long splines, etc].

SYRacing
Posts: 10
Joined: Tue Jan 10, 2017 11:20 am

Re: Running 57" rear leafs up front

Postby SYRacing » Fri Feb 17, 2017 11:36 am

I'm not too concerned with driveshaft, I'm running super duty 1350 CV with 1410 at the axle. I have built the shaft to allow enough slip for 6" compression, 6" droop. I have 12.5" shocks.

I have some degree plates that I haven't put in to help with the angle too.

Good point on shackle reversal!

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Stuka
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Re: Running 57" rear leafs up front

Postby Stuka » Fri Feb 17, 2017 12:32 pm

Biggest issue with longer front springs is you lose approach angle. As the front sprint mounts have to be moved farther forward. The will also increase axle wrap.

As for the shackle reversal, thats a mixed bag. It will make it harder to bend the main sprint (military wrap springs fix this), but it also makes it harder to climb obstacles and can cause significant nose dive during hard braking, although I doubt thats an issue for you as that looks pretty strictly a trail rig.
1981 J10 AMC 258 with HEI and Weber 32/36 DGEV Carb, T176, NP208, D44/M23 with 4.56 gears and Detroit Locker, 6" lift, 33x12.50 Cooper STT's, BJ's Offroad Rear Dozer Bumper.
2017 JKU Rubicon Lifted and stuff
Pevious Jeeps: 1975 Cherokee, 2008 JK, 2005 KJ, 1989 XJ

rocklaurence
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Re: Running 57" rear leafs up front

Postby rocklaurence » Sat Feb 18, 2017 9:32 am

Im Diggin you Rig. It's all about setting it up and having fun! 8-) Too many spend all their time and money building the Ultimate Rig and never finish it or have fun. For example: the Dana 60 debate for first time builders. If you have the money and resources--do it. However, if a D60 is going to break the bank or seriously delay the build, run the D44. Have fun and then if it breaks, you know that you need something larger.

SYRacing
Posts: 10
Joined: Tue Jan 10, 2017 11:20 am

Re: Running 57" rear leafs up front

Postby SYRacing » Sun Feb 19, 2017 10:13 pm

Thanks for the compliments.

This rig started out like you describe...gotta have this and that which is why it's taken close to 8 years to build.

I think I ended up with a decent setup crawl ratio and capability wise. Still need to do 35 spline outers and hydro assist steering but it gets around good.

After using it awhile I've flattened the front springs so they are never really done are they

rocklaurence
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Re: Running 57" rear leafs up front

Postby rocklaurence » Tue Feb 21, 2017 7:47 am

Often when its DONE--it gets sold :D


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