Short arm down-travel limits

[freedom_in_4low]

how far can a TJ shortarm droop? In terms of maximum extended shock length measured between the shock mounts.

What causes this limit?

What are some ways to improve this within the bounds of off-the-shelf parts and simple DIY fabrication?

My situation:
I have Savvy uppers, Rough country lowers, and Currie track bar. The next limit that's popped up for me is the LCA hitting the shock bracket at about 25.5" between the shock mounts (I haven't set my caster yet, so this may go up or down - links are currently approx stock length so maybe I can dial some out and raise the shock mount). The passenger stops a little before contact at 24.5"; I think the track bar is binding once the driver side stops, and I *think* if I free up the driver side, the passenger might keep going as well, but I have no way to know without doing it.

I'm not just pushing it for the sake of droop - I'm finding that with a 4" lift, I'm getting pretty light on downtravel at just about 3-3/8". Since this whole project started because I hated the 2.5" downtravel in my rear shocks, that number makes me nervous and I'd like to see at least 4 if I can't get 5 to match my uptravel. I'm thinking of clearancing the bracket around the LCA, or maybe getting some LCA's with a bend like Core 4x4. , and then I wonder, what would the next limit be? If I address this one, where is the next limit where things just bind up and won't go any farther?

 

[SvtLdr]

I think you'll find that as the axle droops down it tends to travel towards the drivers side due to the track bar (or possibly steering). Similar to the arc that control arms create (front to back). My guess is you're pretty close to the limit already. Disconnect your lower arms and droop the axle out. Observe how far it moves to the driver side on its own.

 

[BuildBreakRepeat]

I would trim the bracket so the arm doesn't contact it.

 

[jjvw]

Short arms can easily support 11" front, 12" rear travel shocks divided in half. The arms are not the practical limits to flex or droop.

 

[freedom_in_4low]

Short arms can easily support 11" front, 12" rear travel shocks divided in half. The arms are not the practical limits to flex or droop.

good to know, and that confirms my hope/suspicion. I'll hit that bracket with the grinder and see what I can get out of it. If I get another inch I'll be satisfied, another 2 I'll be happy, and 2.5" will fully utilize the length of the 255 with 5 up/5.9 down and and I'll be thrilled.

Definitely gonna need to get those YJ brake lines installed...

 

[astjp2]

Well you can run 12 travel in the rear with 6 up and down with short arms, dat enuf 4 ya?

 

[freedom_in_4low]

Well you can run 12 travel in the rear with 6 up and down with short arms, dat enuf 4 ya?

That would be plenty. Assuming a body lift is involved to get some at the top end? With factory bump stops I could have 11.75 in the rear but I have 2" bumps to keep the track bar bracket out of the floor. And of course I'd need to outboard or figure out a shock with a compressed length only 1/2" more than it's travel.

 

[BuildBreakRepeat]

That would be plenty. Assuming a body lift is involved to get some at the top end? With factory bump stops I could have 11.75 in the rear but I have 2" bumps to keep the track bar bracket out of the floor. And of course I'd need to outboard or figure out a shock with a compressed length only 1/2" more than it's travel.

The body doesn’t affect shock length at all. All shock mounting locations are on the frame. Out-boarding is how you get a 12” travel shock to bottom out exactly at hard bump.

 

[freedom_in_4low]

The body doesn’t affect shock length at all. All shock mounting locations are on the frame. Out-boarding is how you get a 12” travel shock to bottom out exactly at hard bump.

No but it has to do with how high the axle can go before things hit the floor. A body lift would let me get rid of some bump stop, and then outboard the shocks to take advantage of the extra inches of uptravel clearance.

 

[-T.]

So this will be one of those Jeeps we have to fix on the trail because the springs drop out of it, or because the control arms try to fold backwards under the Jeep. I can't wait.

 

[jjvw]

So this will be one of those Jeeps we have to fix on the trail because the springs drop out of it, or because the control arms try to fold backwards under the Jeep. I can't wait.

How many outboards have you done?

 

[BuildBreakRepeat]

So this will be one of those Jeeps we have to fix on the trail because the springs drop out of it, or because the control arms try to fold backwards under the Jeep. I can't wait.

Misguided viewpoint

 

[BuildBreakRepeat]

No but it has to do with how high the axle can go before things hit the floor. A body lift would let me get rid of some bump stop, and then outboard the shocks to take advantage of the extra inches of uptravel clearance.

1.25” Bl is the highest return modification you can make!

 

[BuildBreakRepeat]

No but it has to do with how high the axle can go before things hit the floor. A body lift would let me get rid of some bump stop, and then outboard the shocks to take advantage of the extra inches of uptravel clearance.

Track bar bracket I’m assuming?

 

[freedom_in_4low]

So this will be one of those Jeeps we have to fix on the trail because the springs drop out of it, or because the control arms try to fold backwards under the Jeep. I can't wait.

pretty curious how the control arms could fold backward with a track bar and 26" long shocks.

Or how my 20.5" free length springs could escape their retainers, compress themselves to 10" to fit between the bump stops and then jump over 4.5" of bump stop and spring centering pad to get out.

But mostly just curious about what kind of hacks you've been wheeling with. ¯\_(ツ)_/¯

 

[freedom_in_4low]

Track bar bracket I’m assuming?

yeah, my track bar bracket is about 1/4" from the floor with 2" bump stops. If that wasn't there, I assume the UCA mounts would be next.

 

[jjvw]

Even with evenly divided travels on a 11" or 12", it isn't impossible to have the axle walk under the Jeep and yank a shock out of it's mount. Hit an undercut ledge hard enough and bad things can happen. A longer arm will help prevent it, but think a bit about how common this problem is.

Solving the falling out springs problem is easy and retainers are not even needed.

 

[freedom_in_4low]

Even with evenly divided travels on a 11" or 12", it isn't impossible to have the axle walk under the Jeep and yank a shock out of it's mount. Hit an undercut ledge hard enough and bad things can happen. A longer arm will help prevent it, but think a bit about how common this problem is.

Solving the falling out springs problem is easy and retainers are not even needed.

I can definitely see it without a track bar, but it's hard to picture how that happens with one.

Yeah, springs falling out is nowhere near a concern for my rig at this point, even if I left the retainer out. It just becomes loose enough to rotate in place by hand at 25.5" shock length, and still requires a pry bar and the bump stop extension removed to get out. With the additional droop I'm looking for, there's still not a chance. That said, I do recognize that droop without any spring pressure doesn't really provide any value, so I have no intention of going any further than what the 255's will do, and will likely go with Currie 4" at some point to take up every bit of that space.

 

[jjvw]

Hang a front tire from the fully extended shock and then push the front of the tire into the face of a large step. The angle of the arm may be inclined to go further down and backwards, rather than climb up.

But again, while very real, think about what it takes to get into that situation. From what I've seen, we are far more likely to find the proud droopy guy with ridiculously long shocks and short springs that fall out.

The more immediate and beneficial areas to focus on are balanced shock travels with springs that will support that travel. You are already doing that.

 

[-T.]

You guys are all right. I was in a mood yesterday. I've just been at this TJ thing for a little while, and I've seen this scenario play out over and over again. Cutting back the lower control arm mounts to allow the the arms to get just a liiiitle bit more vertical without enough thought to everything else that can happen, when the reality is that it just doesn't offer a whole lot of benefit aside from good photos. We were playing around with these experiments around the same time the YJ guys were experimenting with buggy springs and Revolver shackles. But this crew at least seems to be putting more thought into the work. And I need to stop and realize that, many times, we're just bench racing here, or just looking for something new to tinker with. Keep them safe. Have fun.