Rough Country 4" lift

[PNW_LJ]

Don't take me as gospel whatever you do.

Ultimately I think being 50/50 makes the most sense, but for situations where you have to choose between biasing one way or another I can come up with a counterargument for every reason I think of in support of doing it either way.

Likewise, I’ve heard the argument go either way, and I’m not yet convinced which path is better (high uptravel or lower COG).

We have a buggy in the family that I wheel with occasionally (sticky 40s, rear steer, tuned 14s, low belly height etc etc). Right now, it’s at 3” of up in the front, maybe 4” in the rear, and it’s insanely stable at highly off camber/articulation situations.

Obviously it’s construction is far from a TJ, but I wonder whether it’s stability is thanks to the low uptravel/COG, or in spite of it.

I’ve played around a bit with various shocks and shock mounts on my Jeep, and thus far, anything less than 4” of up in the rear, is unbearable on a rough road with a soft shock like the rancho. So right now I’m stuck running 6” up/2” down in the rear on these ranchos. I do pay the price offroad, but at least the big bumps a tad less jarring.

 

[jjvw]

Likewise, I’ve heard the argument go either way, and I’m not yet convinced which path is better (high uptravel or lower COG).
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The two are not necessarily mutually exclusive. Those who value up travel for it's many advantages will build it through some combination of added ride height along with clearing the way for the suspension travel to go up.

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We have a buggy in the family that I wheel with occasionally (sticky 40s, rear steer, tuned 14s, low belly height etc etc). Right now, it’s at 3” of up in the front, maybe 4” in the rear, and it’s insanely stable at highly off camber/articulation situations.

Obviously it’s construction is far from a TJ, but I wonder whether it’s stability is thanks to the low uptravel/COG, or in spite of it.

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You need to assign some measurements and context to begin to compare. What does low belly height mean? What is the wheelbase? Is the terrain rough enough to involve dragging the underside and actually relying on the skids?

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I’ve played around a bit with various shocks and shock mounts on my Jeep, and thus far, anything less than 4” of up in the rear, is unbearable on a rough road with a soft shock like the rancho. So right now I’m stuck running 6” up/2” down in the rear on these ranchos. I do pay the price offroad, but at least the big bumps a tad less jarring.

Are you not lifting the rear axle off the ground during high speed runs on rough ground? 6 up/2 down is an unusual shock to be really be stuck with. The shock is way too short.

 

[PNW_LJ]

The two are not necessarily mutually exclusive. Those who value up travel for it's many advantages will build it through some combination of added ride height along with clearing the way for the suspension travel to go up.

Agreed. I’m imagining a scenario such as the aforementioned buggy on air shocks. The current 3” up w/ a 19” belly height versus pumping them up to 5” up with 21” belly height.

I believe the latter would perform better overall, but I’d like to observe how the stability is affected. Running some trails in both configurations side by side is something that I’d like to try.

You need to assign some measurements and context to begin to compare. What does low belly height mean? What is the wheelbase? Is the terrain rough enough to involve dragging the underside and actually relying on the skids?

Belly is around 19.5” at the moment, which is pretty low for 40s and our area IMO. Wheelbase 107ish. The belly skid is pretty dinged up, if that’s any indication.

It is worthy to note that the cross section that the belly takes up is significantly smaller than the LJ’s whale belly. Probably a solid 3-4 times smaller surface area, which definitely makes a difference on the trail.

Are you not lifting the rear axle off the ground during high speed runs on rough ground? 6 up/2 down is an unusual shock to be really be stuck with. The shock is way too short.

I’m not sure, it may have happened but I haven’t observed it. The bigger issue is not enough droop -> wheels in the air, and open diffs makes it worse.

This is on the standard RS55256, paired with Currie LJ springs. Those gave me more lift than expected, even with Currie 4” + 0.75” spacers in front, there’s quite a bit of rake in normal driving.

I might have exaggerated a bit, it’s closer to 3” down. Which isn’t much better. I’m considering some BPEs for now, unless I can find a better shock for the rear.

 

[freedom_in_4low]

Likewise, I’ve heard the argument go either way, and I’m not yet convinced which path is better (high uptravel or lower COG).

Lowest CoG you can achieve with a balanced shock travel.

We have a buggy in the family that I wheel with occasionally (sticky 40s, rear steer, tuned 14s, low belly height etc etc). Right now, it’s at 3” of up in the front, maybe 4” in the rear, and it’s insanely stable at highly off camber/articulation situations.

Obviously it’s construction is far from a TJ, but I wonder whether it’s stability is thanks to the low uptravel/COG, or in spite of it.

The low cog definitely helps. Less uptravel probably doesn't, but how much does it hurt? There is a point where the cog vs uptravel is ideal, is that point always at half the shock travel or is it sometimes less?

I’ve played around a bit with various shocks and shock mounts on my Jeep, and thus far, anything less than 4” of up in the rear, is unbearable on a rough road with a soft shock like the rancho. So right now I’m stuck running 6” up/2” down in the rear on these ranchos. I do pay the price offroad, but at least the big bumps a tad less jarring.

At one point in my TJ I made a change that left me with about 2" of down travel in the rear. The way I perceived it was when I put both left wheels through the same hole and the front seemed to go through it without much fanfare but the rear would drop into it and yank the body down so hard it was trying to toss me out of my own door.

 

[Mike_H]

Don't get wife #4, I would think you would have learned after 3 (maybe 2)...just rent them from now on and save the $$$ for the Jeep!

My father in law has a good friend (both in their late 80s). The friend is a bit "non-politically correct" and is a hoot to talk to. He has recently taken to calling himself Buy-Sexual...in that he pays for his female accompaniment. Must be working for him, last time I talked with him, he was getting ready to leave for India! He travels all over the world, even at 89.

 

[PNW_LJ]

Lowest CoG you can achieve with a balanced shock travel.

How do you define balanced travel? 50/50?

The low cog definitely helps. Less uptravel probably doesn't, but how much does it hurt? There is a point where the cog vs uptravel is ideal, is that point always at half the shock travel or is it sometimes less?

Right, that’s what I’d like to know. An argument for high uptravel is that there’s space for the tire to move up, where a low uptravel build would move the whole body up on the same obstacle.

On the other hand, a low COG build stays low all the time. If we imagine these rigs going straight on a sidehill with no bumps, the one with a lower COG will probably feel more stable?

At one point in my TJ I made a change that left me with about 2" of down travel in the rear. The way I perceived it was when I put both left wheels through the same hole and the front seemed to go through it without much fanfare but the rear would drop into it and yank the body down so hard it was trying to toss me out of my own door.

Interesting, I think I experience something similar on the regular, thought not as violent as you describe it.

 

[jjvw]

How do you define balanced travel? 50/50?


Right, that’s what I’d like to know. An argument for high uptravel is that there’s space for the tire to move up, where a low uptravel build would move the whole body up on the same obstacle.

On the other hand, a low COG build stays low all the time. If we imagine these rigs going straight on a sidehill with no bumps, the one with a lower COG will probably feel more stable?




Interesting, I think I experience something similar on the regular, thought not as violent as you describe it.

50/50 allows the wheels/axles to move without shoving the body around. Building to maintain up travel and achieve 50/50 is more work than a downtravel bias is to build. Maintaining that up travel with 50/50 provides the shock time and distance to do it's work of controlling movement and to do it with potentially nicer valving than less travel.

All of that is about balance.

 

[LONGJP2]

On the other hand, a low COG build stays low all the time. If we imagine these rigs going straight on a sidehill with no bumps, the one with a lower COG will probably feel more stable?

Low COG or not, I would think the weight of 40" tires would keep you feeling pretty stable.

 

[freedom_in_4low]

Right, that’s what I’d like to know. An argument for high uptravel is that there’s space for the tire to move up, where a low uptravel build would move the whole body up on the same obstacle.

On the other hand, a low COG build stays low all the time. If we imagine these rigs going straight on a sidehill with no bumps, the one with a lower COG will probably feel more stable?.

At some point someone here argued that having one side resting on the bump stop made it more stable because it moved the roll center to the bump stop. Thinking about the physics of that, the roll center would be moving farther away and out from underneath the CoG which doesn't seem more stable to me.

I haven't felt bored or spendy enough to build and rebuild my suspension to try all these things out but the idea was...not popular.

Still, I have contemplated what I could do to improve perceived stability on off camber surfaces. I'm at 4.9 up/5.8 down and Currie 4" springs. Shorter shocks or some upper mount mods could get me another inch of up before tire hits fender, and then fender mods could get yet another inch before I have suspension bits meeting one another. But at either of those levels, I'm not sold on whether it makes more sense to keep the ride height and take the uptravel, or drop the ride height and maintain the same uptravel I have now, which by most standards seems adequate. I suppose the answer brings yet another parameter into consideration, which is my 20.5" frame height with LJ wheelbase.

 

[PNW_LJ]

50/50 allows the wheels/axles to move without shoving the body around.

Right, this makes sense. But does this always result in more stability as compared to a LCOG rig?

Building to maintain up travel and achieve 50/50 is more work than a downtravel bias is to build. Maintaining that up travel with 50/50 provides the shock time and distance to do it's work of controlling movement and to do it with potentially nicer valving than less travel.

All of that is about balance.

This makes sense, more so with altered shock mounts and tuned shocks.

 

[PNW_LJ]

Low COG or not, I would think the weight of 40" tires would keep you feeling pretty stable.

Might as well go rockwells and 50s!

At some point someone here argued that having one side resting on the bump stop made it more stable because it moved the roll center to the bump stop. Thinking about the physics of that, the roll center would be moving farther away and out from underneath the CoG which doesn't seem more stable to me.

Interesting.

I haven't felt bored or spendy enough to build and rebuild my suspension to try all these things out but the idea was...not popular.

Still, I have contemplated what I could do to improve perceived stability on off camber surfaces. I'm at 4.9 up/5.8 down and Currie 4" springs. Shorter shocks or some upper mount mods could get me another inch of up before tire hits fender, and then fender mods could get yet another inch before I have suspension bits meeting one another. But at either of those levels, I'm not sold on whether it makes more sense to keep the ride height and take the uptravel, or drop the ride height and maintain the same uptravel I have now, which by most standards seems adequate. I suppose the answer brings yet another parameter into consideration, which is my 20.5" frame height with LJ wheelbase.

Similar situation over here.

With my LJ build, I like the current belly height (4” and tummy tuck), and definitely don’t want to go any lower with my wheelbase and the eventual 35s. I also want to maintain a bare minimum of 4” up. Everything else is on the table, just a matter of cycling the suspension to figure this out.

 

[PNW_LJ]

I’m thinking of taking the buggy out on some obstacles with the current setup (~3-4ish uptravel and 19.5” belly height), and then pumping up the shocks a couple inches and attempting the obstacles again, and then comparing which looked/felt more stable. Just need to get a portable shock refill kit so we can do it on the spot.

Might make for an interesting comparison video if this is something folks are interested in.

 

[jjvw]

Right, this makes sense. But does this always result in more stability as compared to a LCOG rig?
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Focusing too heavily on LCOG at the expense of how the rest of the rig functions is ignoring the total harmony of how the rig functions as a system. A rig that is calm, controlled, and predictable is a stable rig. This extends well into the shocks, swaybars, transmission, steering, any number of physical clearances, and where the weight is and how it is controlled.