Outboard Questions

XCRN

XCRN

TJ Enthusiast
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Jun 1, 2020
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Springfield OH
I am now in the planning and parts procurement stage of an outboard job for my go-fast TJ possibly with a rear non-triangulated long arm. The shocks to be used are ideally 12in Fox 2.0 CD adjustable shocks and looking at using Poly towers, JKS 3in springs and relocating the upper spring perch to be lined up at full compression. I understand that this is not a one size fits all job, but I figured there might be some similarities around what I am trying to figure out.

With that said, ideally I am trying to shoot for no more than 2in of bump stop extension on the rear to maximize up travel. As is, I can probably get away with about 1in of bump stop extension. With those who have done this job, is it possible to use that little bit of BS extension without having a body lift or tub modifications with a 12in shock? Is there a rough measurement from somewhere on the frame to where most top mounting points end up at to get a rough idea on what my compressed shock limits are and get an idea what shock might be feasible when doing a more thorough cycle test than what I did previously?

Running the numbers in my head, I also think that trying to utilize most of the 12in with a 1in bump stop extension, I would likely unseat the spring before getting a full 12in. Is there a better 3in or even 2-1/2 spring that I could use? The JKS springs are 15in extended and should be 11in at ride height according to charts posted here. So in theory I would only get 4in of down travel before it unseats. I am more concerned with up travel for what I do, but I have been airborne a few times so the extra down travel would be nice to have more dampening before bottom-out.
 
The immediate question is if those springs have enough free length to accommodate a 12" travel shock to begin with. There is a reason why the Currie/RockJock 4" spring is used so often with an outboard. And it barely has enough free length for the job.

As for bump stop, you build the shocks to be the hard limit to up travel. Then you build the jounces to fit the shocks to slow down the final bit of shock travel speed as the shock reaches full compression.
 
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To visualize where the shock tower needs to go, you acquire the compressed and extended lengths of the shock. Then you cycle the axles without springs or jounces installed and sway bar links detached. From there you raise and lower the axle to mimic these compressed and extended lengths and see where things need to go to create the desired shock travel bias.

At the same time, you can get a sense of the compressed and free lengths of the spring by measuring the spring seats and compare that to what use are wanting to use.
 
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jjvw said:
The immediate question is if those springs have enough free length to accommodate a 12" travel shock to begin with. There is a reason why the Currie/RockJock 4" spring is used so often with an outboard. And it barely has enough free length for the job.
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That what I was thinking but could not find an answer on how people were getting 12in travel at all. I tried finding the longest free length 3in rears I could and JKS was the only one not discontinued or what seemed like perpetual back order that is on the excel spread sheet found somewhere on this forum.

What you say about the BS makes sense and that is what I was able to achieve with the front doing that recently. I think there is a 1/4" difference from jounce being fully compressed to shock bottom. What I am not sure is about roughly how high up over the frame is a 12in shock usually placed so I can see if the shock can compress enough to get close to the jounce. But ill have it back on jack stands this week so I can get a better idea thoroughly checking. It just seems like eyeballing it, at 18in compressed to the rough idea where the mounts ends up at looks like it would not fit.
 
XCRN said:
...What I am not sure is about roughly how high up over the frame is a 12in shock usually placed so I can see if the shock can compress enough to get close to the jounce. ...
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This is a well documented procedure... 😉

Screenshot_20240422_104126_Google.jpg
 
The thing about the tower height is that it is directly related to both the ride height created by the spring and the compressed length of the shock.

If you do not have the springs to know the ride height, all you can do is estimate the ride height. Though, the actual work of cutting in and attaching the shock mounts should not happen until you have the springs and know the ride height.
 
jjvw said:
The thing about the tower height is that it is directly related to both the ride height created by the spring and the compressed length of the shock.

If you do not have the springs to know the ride height, all you can do is estimate the ride height. Though, the actual work of cutting in and attaching the shock mounts should not happen until you have the springs and know the ride height.
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Rear spring are going in this week but with the uncorrected perches. Ill be doing that with the OB job, but it sounds like that would not affect ride height at all.
 
Cutting and moving the spring perch is incredibly easy.
Don't forget that you can change the location of your axle shock mounts. The factory mounts hang insanely low. I suggest mounting your frame shock mounts as high as possible to allow your axle mounts to do the same. If you're doing the work to outboard you might as well do it all.

Obviously with coil springs you're limited to your spring compression length so you'll have to measure for both spring and shock compression.

Also, since you mentioned go-fast, DEFINITELY use limit straps to save your shocks. If your spring unseats at full droop before your limit strap extends then you can also use spring retainers on your perches.
 
Dev said:
....

Also, since you mentioned go-fast, DEFINITELY use limit straps to save your shocks. If your spring unseats at full droop before your limit strap extends then you can also use spring retainers on your perches.
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This is why he needs springs with enough free length to stay contained in the seats by the extended shocks. Then he can skip the limit straps.
 
XCRN said:
Rear spring are going in this week but with the uncorrected perches. Ill be doing that with the OB job, but it sounds like that would not affect ride height at all.
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Moving the upper seats can absolutely alter the ride height if you want it to.
 
XCRN said:
They can be added on later by accutune but for like $300/ea.
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Correct. Last I discussed it with someone in the know, 2.0s can be converted to DSC reservoirs. But all that remains of the original 2.0 is the shock body tube.
 
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jjvw said:
Are DSCs available as an off the shelf 2.0 now?
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Not for smooth bodies. Fox, AccuTune, Kartek offer them as an "upgrade" service. The price has gone up since I had two DSCs added to two coil overs back during the shock shortage, though.
 
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You would be better served by using the RockJock coils and modding the mounts to lower you that inch if that is the height that you desire. You need the free length or the longer shocks are there just so you can look cool on a RTI ramp.

I would not discount having to do some tub work either to go with the lower bumstops.
 
Blackjack said:
You would be better served by using the RockJock coils and modding the mounts to lower you that inch if that is the height that you desire. You need the free length or the longer shocks are there just so you can look cool on a RTI ramp.

I would not discount having to do some tub work either to go with the lower bumstops.
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Ill look more into the RJ coils and recessing the mount in. The free length being 2-1/2in larger before sacrificing the 1in looks like a solid option and I can move the JKS to my LJ.
 
XCRN said:
I’ll look more into the RJ coils and recessing the mount in. The free length being 2-1/2in larger before sacrificing the 1in looks like a solid option and I can move the JKS to my LJ.
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Since you’re doing the work to outboard the shocks for additional travel, why not just go ahead and eliminate the coil spring by switching to coil-over shocks? Doing so will open up the ability to tune your suspension to better suit your go fast driving style.
 
Havasu said:
Since you’re doing the work to outboard the shocks for additional travel, why not just go ahead and eliminate the coil spring by switching to coil-over shocks? Doing so will open up the ability to tune your suspension to better suit your go fast driving style.
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Since this is his first outboard, do you care to walk him through the specifics of squeezing coilovers into factory width axles?
 
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