Control Arm Lengths for Tons? - JKowners.com : Jeep Wrangler JK Forum
 
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post #1 of 7 Old 11-29-2018, 02:15 PM Thread Starter
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Control Arm Lengths for Tons?

Hey folks. Going tons and need to revisit control arm lengths.

What I am going to:
A set of tons that has had the C's, spring perches, brackets and such adjusted for my lift height.

What I am coming from:
Stock axles. And I don't remember what I set the Metal Cloak control arms to. Their recommendations only go to 2.5" lift and I've been at 4" most of the time, so I set my control arm lengths to something a little different than the 2.5" standard and don't remember what that was.


I want to remove all of the control arms anyway and take apart the bushings for inspection and to lubricate them again.


Anyway, what is a good starting point for the control arm lengths going back together? Assuming 4" lift (linear coils) with 3" bump stops? Stock lengths because of the geometry corrected axles?
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post #2 of 7 Old 11-29-2018, 05:41 PM
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Have you reached out to Metalcloak and seen what they recommend as a starting point? They have lots of rigs running tons and there arms out there.

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post #3 of 7 Old 11-30-2018, 07:36 PM
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No way to tell until you actually have the axles under the jeep.

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post #4 of 7 Old 11-30-2018, 07:41 PM
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I would say it depends on how much caster is built in and the angle of separation for your pinion.

Last edited by spinuck; 11-30-2018 at 07:47 PM.
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post #5 of 7 Old 12-01-2018, 07:57 AM Thread Starter
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Metalcloak does publish the lengths for the stock length as well as for 2.5" to 3.5" of lift on stock axles.

https://www.metalcloak.com/JK-Wrangl...Arm-p/7105.htm

I am getting Fusion4x4 axles and those are totally custom so I can have Dan put in as much caster as I need plus he adjusts spring perches and I think control arm attachment points (front and rear).

I don't need to adjust the control arms to compensate for pinion angles, caster or spring perches but I figured that with the axles traveling within a different range that is lower in the arc that I should at least be compensating for the change in wheel base somehow. I want do do this without affecting the pinion angles etc designed into the new axles.

Does this necessarily mean that I can lengthen all arms by the same about over the stock lengths?
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post #6 of 7 Old 03-23-2019, 01:44 PM Thread Starter
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I'm slowly getting my build done. The tons are finally installed and I am finalizing the control arm lengths.

On the front, I went with MetalCloak's suggestion of [email protected]/16" and [email protected]/4". The pinion angle looks good on the front but I have not been on an alignment rack yet to confirm the caster. The front is probably fine.

The rear is where I am spending my time at the moment because the pinion is to high and does not form a straight line with the drive shaft. I started by using the Synergy specs on the rear control arms because they are slightly shorter than what MetalCloak publishes and was trying to avoid pushing the axle back to far .

The shortest that I can get the MetalCloak UCAs to is 17-5/8" which is still slightly longer than stock (17-7/16"). I'll have to lengthen the LCA now to compensate. Stock, the rear LCA is 19-3/4" and I set it to Synergy's spec at 20-1/4". Now I'll try the MetalCloak spec of 20-7/16" for the rear LCA but I suspect that won't be enough.

I read through another thread here on JKO that suggests you want the pinion angle a degree or two smaller than the driveshaft angle because under power, it will raise up slightly.

The pinion was way to high with the rear control arms set at:
UCA: 18-1/4"
LCA: 20-1/4"

Then I shortened the UCA as much as I could and the pinion is still a tad high.
UCA: 17-5/8"
LCA: 20-1/4"

I'm going to grab a beer and set it up as follows and see where it lands me but I suspect I will have to kick out the LCAs a little more. There's a certain degree of trial and error here.
UCA: 17-5/8"
LCA: 20-7/16"

The Fusion4x4 housings have the brackets welded on already and and compensate for some pinion angle change. I told them I had a 4" lift and then promptly swapped out my coils to 3" so I might be working against myself slightly with that change.
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post #7 of 7 Old 03-25-2019, 08:36 PM Thread Starter
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Okay, the winning numbers for me to get the ideal 2* difference between the pinion and the drive shaft was with these rear control arm lengths:

UCA: 17-5/8"
LCA: 20-7/8"

Keep in mind that this is for 1 ton axles that have larger diameter tubes and also some geometry correction for the pinion already built in with the way the JK brackets were welded to the axle.

I did not have to max out my LCAs. Max "safe" length as per MetalCloak support on the LCA is 21-1/4". The minimum length of threads that you need to have in contact between the female threaded control arm tube and the male threaded forged end is equal to the diameter of the male threads on the forged end. So about 1.5" of contact IIRC (without running back down to the garage).
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