Why not rear sway bar disconnect?

[dcmdon]

I know nothing about jeeps but a fair amount about how suspension works, so maybe I'll give you an explanation that makes sense.

Its all a trade off.

You would get better articulation with both disconnected. There is no doubt about that. But its at some point the vehicle becomes so unable to control roll that you have other issues.

Everyone says "coils need it". But they offer zero explanation. That seems frustrating to you. I get it.

A spring is a spring. Right? Right, . . .. but. Leaf springs have friction between the leaves as they work against each other which actually provides a bit of damping. Coil springs don't. Maybe that is why, I don't know.

But I do know that leaf springs don't provide inherently more roll control. Maybe how they are actually implemented in Jeeps makes a difference. But a spring is a spring.

If your roll resistance becomes too low, then you have to stiffen the springs themselves which becomes self defeating.

An anti-rock system is just a well tuned, expensive soft sway bar. There's no magic to it. you could achieve the same thing with a stock setup with a thinner sway bar.

There is no free lunch. Everything is a trade off.

I would be afraid of the anti-rock system installed only on the front in a street driven Jeep because of its possibly dangerous impact on on-road handling. It will feel fine at low speeds. But a vehicle's tendency to over or understeer is greatly impacted by roll stiffness.

Soften front roll stiffness and the vehicle tends to oversteer unpredictably. This is very dangerous if it happens during an accident avoidance maneuver.

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[Pescatoral Pursuit]

so maybe I'll give you an explanation that makes sense.

There is no free lunch. Everything is a trade off.

Gosh thanks man. I got it a few posts back;

I think what I'm reading here is that you need the lesser of two weevils in order to give the body some stability;
IOW, the body is too disconnected from the suspension without at least one sway bar and would be floating on the springs and shocks.

The simple thing no one wanted to just say: The vehicle body is too unstable only connected by suspension.

there's no magic to it.

But I still wasn't sure if some magic wasn't involved so appreciate you putting that one to bed. Whew.

 

[Jeepin' John]

The simple thing no one wanted to just say: The vehicle body is too unstable only connected by suspension.

This hasn't been my personal experience wheeling multiple jeeps and a land rover discovery with the rear bars disconnected. Disconnecting any sway bar reduces body roll resistance, but jeeps don't spontaneously flop over with the rear sway bar disconnected. I think it's just been repeated on the forums so many times to not disconnect your rear bar that people accept that without trying it out for themselves and seeing which way they prefer. Having more stability from flex going down a technical trail at a steep decline angle is why i prefer the disconnected rear bar

 

[dcmdon]

This hasn't been my personal experience wheeling multiple jeeps and a land rover discovery with the rear bars disconnected. Disconnecting any sway bar reduces body roll resistance, but jeeps don't spontaneously flop over with the rear sway bar disconnected. I think it's just been repeated on the forums so many times to not disconnect your rear bar that people accept that without trying it out for themselves and seeing which way they prefer. Having more stability from flex going down a technical trail at a steep decline angle is why i prefer the disconnected rear bar

Its going to be vehicle specific. How much roll stiffness is provided by the base springs and how much is provided by the sway bars.

A Rover with air springs may do better because the air springs are highly progressive.

One other thing is that the higher the center of gravity of the vehicle is the stiffer the sway bars need to be to control thngs.

My wife's Miata was able to have a decent ride and very little roll because the CG was so low. In contrast, my relatively tall STi needed super stiff roll bars. It handled a little better but rode a lot worse.

A Jeep takes that to an extreme being much taller and needing either stiff springs or roll bars to control roll.

 

[dcmdon]

Gosh thanks man. I got it a few posts back;

Sorry. ADD kicked in. Must have missed it. ;-)

 

[Wheelin98TJ]

This hasn't been my personal experience wheeling multiple jeeps and a land rover discovery with the rear bars disconnected. Disconnecting any sway bar reduces body roll resistance, but jeeps don't spontaneously flop over with the rear sway bar disconnected. I think it's just been repeated on the forums so many times to not disconnect your rear bar that people accept that without trying it out for themselves and seeing which way they prefer. Having more stability from flex going down a technical trail at a steep decline angle is why i prefer the disconnected rear bar

I had a TJ without a rear sway bar on a couple different occasions.

Did an axle swap, didn't swap over the sway bar brackets. Eventually they went back on because performance sucked without the rear sway bar. Body flopped everywhere.

Another occasion, broke a rear sway bar link at the Badlands coming out of the drainage tunnel. Performance sucked the rest of the day. Fixed it when I got back home.

Could be my shocks were considerably softer than yours. Maybe my Jeep was taller and had softer springs. Not sure. I just know it was better with the rear sway bar.

 

[The Kracka]

The rear sway bar help keep the body stable, less roll back and forth. Disconnecting doesn't help articulation, proper length sway bar links and bump stops for your setup is going to provide the best results. In this video you can see where the rear sway bar actually aids in the ability of driving up a flex ramp.

 

[chorky]

Coil suspensions work better with sway bars.

https://www.jlwranglerforums.com/forum/threads/rear-sway-bar-disconnect-removal.23549/#post-723312

The rear sway bar help keep the body stable, less roll back and forth. Disconnecting doesn't help articulation, proper length sway bar links and bump stops for your setup is going to provide the best results. In this video you can see where the rear sway bar actually aids in the ability of driving up a flex ramp.

there is a important factor here that everyone is missing. Everybody always thinks about articulation when discussing sway bar disconnects. This is not the only reason to use them. Let me explain by asking a simple question. Who here has noticed the ride quality improvement when the front sway bar is disconnected?? “Oooo. ME!!!!”

See, disconnecting the front sway bar does two things. 1) it allows increased articulation like everyone already knows about. And 2) it increases ride quality. How? By reducing the side to side motion

See the purpose of a sway bar is to help keep tires planted to the ground when cornering. When body Roll begines from taking a corner at speed, lets say in a left turn, the vehicle naturally wants to lift on the left side and roll toward the right Thanks to gravitational forces. The sway bar (or rather anti-sway bar) has resistance to torsional movement so it transfers the rolling force being applied to the right side and pushes it back to the left. Thus reducing a rolling motion. Antirock understands this by lowering the twisting force on their antirock bars allowing more ‘twist’ thus allowing more articulation. Anyone who has an antirock system or straight up removed the sway bar knows this feeling.

But on to point #2 that everyone ignores. Seeing as how I tried having this conversation on a previous thread and received the same backlash. If you notice how much more comfortable the front rides with a disconnected sway bar, the same can be applied to the rear. See when the sway bar is attached and you go over undulating surfaces, you will feel the vehicle rock back and forth. This is because as your left tire goes down into a slump (or up over a bump) the sway bar ’sees’ that as twisting rotational force and applies that force to the opposite tire just like it does with body roll going around a corner. The problem here is you are not cornering. So depending on the speed of travel and the bump/dip size and spacing, what can happen is a violent side to side motion as motion increases upon itself eventually taking over the dampening rate of shocks. This is noticed in the ‘rubicon bounce’.

Now anyone who has ever disconnected the front sway bar and driven on a undulating surface, such as a forest service road, understands this well. Because as the front tires go over a bump/dip the axle articulates freely and easily since there is no restriction in place to be applied to the opposite tire since the sway bar is disconnected. Now as soon as the rear tires go over the exact same dip/bump, suddenly you (may) get a violent side to side thrash because that rotational force IS applied. The purpose of a anti-sway bar is to prevent, within an engineered level, this side to side movement.


So. If the rear sway bar was disconnected exactly like the front, the ride over these dips/bumps would be heavenly like on a cloud. Now this would not necessarily apply to rock crawling and it would be dangerous on the highway as body roll would be significant. But on a dirt road or mild off road, the comfort level would be exponential.

If yoh dont believe this, next time you disconnect the front sway bar, pay very close attention to the feel of the vehicle as the front tires go over bumps/dips and then pay very close attention to how the feel is when the rear tires travel the exact same bumps/dips at the exact same speed. This effect can also be felt in a parking lot going over a speed bump at an angle to simulate uneven ground.

So. A rear sway bar disconnect is VERY practical for those of us wanting to maximize comfort. I dont give a rip about ‘flex’. That has zero bearing on my personal use case and choice of lift. Consider other reasons for lift options before naysaying a rear disconnect option. I cant believe that in all the crazy wisdom of ’offroaders’ people cannot think outside the box and see this.

 

[CrazyCooter]

The rear bar rate is so light that it's not really doing much in comparison the the rear coil spring rates. If the shocks are sized appropriately, the coil will be just trying to drop out as the extended shock limits any more articulation.

Any more flex beyond the point where the tire no longer has weight on it say on a ramp is just poser factor. You are much better off when lockers are present to use the bar to further cross load the tires with traction.........

In the case of a light cargo and light spring rate build, I'm in favor of adding a little (about 10%) rear bar. Same goes for a top heavy overland build.

I can't find my notes with exact specs, but the standard Antirock bar is a little lighter when used with the supplied double sheer brackets.

The rear bar is only like 95lb and can be moved by hand vs the MUCH heavier front, so the rear does not have a huge impact on ride quality, where the front is HUGE. As @chorky points out above, the ride quality improves when the front is disconnected. This is why I like to incorporate the dual rate front bar links into my builds, but it does introduce another factor that has to be properly tuned into the build.

 

[chorky]

The rear bar rate is so light that it's not really doing much in comparison the the rear coil spring rates. If the shocks are sized appropriately, the coil will be just trying to drop out as the extended shock limits any more articulation.

Any more flex beyond the point where the tire no longer has weight on it say on a ramp is just poser factor. You are much better off when lockers are present to use the bar to further cross load the tires with traction.........

In the case of a light cargo and light spring rate build, I'm in favor of adding a little (about 10%) rear bar. Same goes for a top heavy overland build.

I can't find my notes with exact specs, but the standard Antirock bar is a little lighter when used with the supplied double sheer brackets.

I dont think that is entirely correct though. On my last truck I removed both sway bars after a custom suspension and can say with experience that off highway it was exponentially more comfortable. The sway bars push the vehicle to the opposite side of a bump by design to reduce body roll when cornering at speed. Even if it is at a low twist resistance. The front on the JTR being disconnected is way more comfortable than the the rear because the axle can freely move. So the rear should follow suit. Now cornering and off camber would be more sketchy of course. But that wouldnt be the use case.


who makes a dual rate front bar? That sounds really slick! Thats interesting the rear bar is that light. Do you know what the helwig bar is that a lot of folks use?

 

[CrazyCooter]

I dont think that is entirely correct though. On my last truck I removed both sway bars after a custom suspension and can say with experience that off highway it was exponentially more comfortable. The sway bars push the vehicle to the opposite side of a bump by design to reduce body roll when cornering at speed. Even if it is at a low twist resistance. The front on the JTR being disconnected is way more comfortable than the the rear because the axle can freely move. So the rear should follow suit. Now cornering and off camber would be more sketchy of course. But that wouldnt be the use case.


who makes a dual rate front bar? That sounds really slick! Thats interesting the rear bar is that light. Do you know what the helwig bar is that a lot of folks use?

Yes absolutely disconnecting the rear will make some difference as the energy from the tire following the terrain is transmitted to the chassis, but it's going to depend on the actual rate of the bar. Then factor in that we ride in the seat closer to the front axle than the rear?

The rear 95lb bar I can move by hand, but the front you can't budge, so naturally the front will make much more difference.

Some guys like Genrite on the Tracer TJ builds on run a huge rear bar and no bar up front. This pretty much makes the chassis do what the rear axle says which works great for climbing rocks and exiting corners on the throttle, but in my opinion sucks horribly for braking into corners on the pavement. Combine that with the light valving they spec the King shocks with and it's a white knuckle experience to drive to the trail.

I do not know what the rate is on the Helwig bar, but it's MUCH higher than the OEM rear bar. You can't move that one much by hand either. In my opinion it's too much for most poeple who dual sport their rig, but the truck I installed on on had a heavier camper, Decked box, cab roof rack and RTT, so it was really top heavy.

It's quite possible that the roughness while your bars are hooked up are a product of not enough rebound damping in the shocks. There is a fine line between not having too much in a strait line and not having enough when cornering or one wheel being loaded.

 

[chorky]

Yes absolutely disconnecting will make some difference as the energy from the tire following the terrain is transmitted to the chassis, but it's going to depend on the actual rate of the bar. Then factor in that we ride in the seat closer to the front axle than the rear?

The rear 95lb bar I can move by hand, but the front you can't budge, so naturally the front will make much more difference.

Some guys like Genrite on the Tracer TJ builds on run a huge rear bar. This pretty much makes the chassis do what the rear axle says which works great for climbing rocks, but in my opinion sucks horribly for braking into corners on the pavement. Combine that with the light valving they spec the King shocks with and it's a white knuckle experience to drive to the trail.

I do not know what the rate is on the Helwig bar, but it's MUCH higher than the OEM rear bar. You can't move that one much by hand either. In my opinion it's too much for most poeple who dual sport their rig, but the truck I installed on on had a heavier camper, Decked box, cab roof rack and RTT, so it was really top heavy.

thats interesting that the front bar is stiffer than the rear. It makes sense from a cornering perspective on the highway since it is the front wheels initiating and controlling a turn, but being a truck I would have expected the rear bar to be the stiffer one to control carrying a load. But maybe not being as the payload is low compared to full-sized trucks. is it typical for the front bars to be stiffer or is that just a JT thing?

 

[CrazyCooter]

thats interesting that the front bar is stiffer than the rear. It makes sense from a cornering perspective on the highway since it is the front wheels initiating and controlling a turn, but being a truck I would have expected the rear bar to be the stiffer one to control carrying a load. But maybe not being as the payload is low compared to full-sized trucks. is it typical for the front bars to be stiffer or is that just a JT thing?

To simplify: Springs carry the load, bar helps control the roll in corners/transfers corner weight, shocks damp the overall spring combined spring rate package and control bottoming?

I too often see people throwing parts together to help a certain characteristic, but one always affects the other in a negative way and it turn into a can of worms. Common Example: Installing air bags to help sway in an overloaded camper setup say on an F250. Yes it "might" help, but usually it creates a rebound damping issue do to the increase in combined spring rate and amplifies the wobbling because the friction is reduced as the leaf springs are unloaded with the bags supporting so much of the weight.

I'm not a officially educated "Engineer" so I don't have all of the proper technical terms, but I know how to make it work together properly!

If the chassis gets weird "After" a bump or series of bumps, I have found it to be a rebound issue. If it's weird "During" the bump it's compression.

 

[CrazyCooter]

@chorky

I edited that last line of the previous post with critical info to diagnose a damping issue after you read it.......

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