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Discussion Starter · #1 ·
Regularly hear people saying a rear swaybar helps front flex, which has always been opposite to what I felt offroad but I've never seen anyone actually measure it. So after messing around with my suspension recently I took some measurements of it fully flexed up driving the LF up the start of a big spoon drain that acts like a ramp just down the road from my place. It's only a 2" lift. Measurements taken from under the lower edge of wheel to edge of flare.

Rear swaybar ON. LR off ground.
LF 641 RF 904
LR 960 RR 583

Swaybar disconnected. No more traction to drive up further but all wheels still on the ground.
LF 621 RF 919
LR 976 RR 545

LF and RR just touching bumpstops, so that's about as good as you can hope for a 2" lift to flex I guess, apart from my crappy Pedders shocks limiting droop travel. But stock length shocks were not the limiting factor with the rear swaybar connected!

The differences were:
FRONT: 20mm more bump, 15mm more front droop. Total 35mm more front flex without rear swaybar.
REAR: 38mm more rear bump , 16mm more droop. Total 54mm more rear flex without rear swaybar.
And 58mm more diagonal LF to RR bump travel
 

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The attachment of the sway bar is more to control the position of the body relative to the axles throughout travel, not just it's effect at maximum travel. It's about working both axles more evenly at the same time rather than just having the rear flex all the way to max travel before the front starting to do anything.

It's great to see someone do some testing and produce some results for discussion. Something that we probably don't do enough of here.

It sounds like you need a set of longer sway bar links if that is what is restricting rear travel. You might be surprised what doing that does to the front end as it will shift the body back the other way. Let me know if you want to test that out, I have some spare longer links sitting around that you're welcome to borrow.
 

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Regularly hear people saying a rear swaybar helps front flex

Rear swaybar ON. LR off ground.
LF 641 RF 904
LR 960 RR 583

Swaybar disconnected. No more traction to drive up further but all wheels still on the ground.
LF 621 RF 919
LR 976 RR 545
You have lost me ??, looks like a win with the sway bar on. When I ran rear standard sway bar I had the opposite problem the rear would lift a wheel before the front. There is no point trying to compare our suspension set-ups due to the fact they are both complete different components used.

What people keep forgetting is it is not 1 component of your suspension that is going to give you great ride/flex, is't a complete suspension package where everything works together aiding each other.
 

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Discussion Starter · #5 · (Edited)
Bogger, it's all explained in the post. Try reading the bits you left out. This bit in particular might help:
The differences were:
FRONT: 20mm more bump, 15mm more front droop. Total 35mm more front flex without rear swaybar.
REAR: 38mm more rear bump , 16mm more droop. Total 54mm more rear flex without rear swaybar.
And 58mm more diagonal LF to RR bump travel
It's not about the numbers! Or bigger "flex" It's about making the front and rear work better together. Driving up a ramp doesn't really prove anything.
so you think the front and rear work better together when they're not flexing as much, not getting as far up an obstacle, and lifting a wheel off the ground sooner?

personally, I reckon they're working better together when the car goes further up the obstacle, keeps the wheels on the ground and gets the most flex possible out of both ends.
 

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Discussion Starter · #6 · (Edited)
The attachment of the sway bar is more to control the position of the body relative to the axles throughout travel, not just it's effect at maximum travel. It's about working both axles more evenly at the same time rather than just having the rear flex all the way to max travel before the front starting to do anything.

It's great to see someone do some testing and produce some results for discussion. Something that we probably don't do enough of here.

It sounds like you need a set of longer sway bar links if that is what is restricting rear travel. You might be surprised what doing that does to the front end as it will shift the body back the other way. Let me know if you want to test that out, I have some spare longer links sitting around that you're welcome to borrow.
You're partly right. A sway bar is a simple torsion bar that tries to return to its normal position. The extended sway bar arm wants to return to its normal position every bit as much as the compressed arm does. You said it tries to control the position of the body relative to the axle, and that's partly true. On the compressed side where the swaybar is pushing down on the axle and up on the body, you can't push the axle and wheel into the ground, so the resultant force pushes the body up. On that side you can say the swaybar is trying to control the position of the body relative to the axle. But on the other side the sway bar is pulling up on the axle and down on the body. The axle is lighter than the body, so the resultant force lifts the axle and the wheel off the ground. And that's exactly what the test confirms.

Also note that first post says the LF and RR are both reaching the bumpstops without the sway bar, so it's not just having the rear flex all the way to max travel before the front starting to do anything.
 

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You have lost me ??, looks like a win with the sway bar on. Either way you need to try a currie or ACF torsion bar set up. I would gladly try mine against standard or superior super flex sway bars. Full flex with out compromise.

Why would the type of swaybar make any difference? As long as there is no binding and the rate is the same you should achieve the same flex with a stock style bar VS a currie etc
 

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I haven't done measurements but also have the Pedders shocks with 2 inch lift and swaybar extensions on rear, I find I lift wheels quicker than others so believe the shocks are limiting factor.
 

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Discussion Starter · #9 ·
The Pedders 2" foam cell shocks in my car for the past few years are exactly standard length front and rear in both compression and extension. Pretty ****! But as I found in that test, the stock length shocks were not the limiting factor with the rear swaybar connected. The factory rear swaybar lifts a rear tyre well before the shocks are maxed out.
 

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The Pedders 2" foam cell shocks in my car for the past few years are exactly standard length front and rear in both compression and extension. Pretty ****! But as I found in that test, the stock length shocks were not the limiting factor with the rear swaybar connected. The factory rear swaybar lifts a rear tyre well before the shocks are maxed out.
I bet you swaybar is not setup correctly
 

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Discussion Starter · #11 ·
however you set up a swaybar, it will always lift a wheel sooner than no swaybar. You cannot prevent them from applying a lifting force to the wheel that is in droop, and resisting compression on the other side. That is exactly what they are designed to do.
 

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Why would the type of swaybar make any difference? As long as there is no binding and the rate is the same you should achieve the same flex with a stock style bar VS a currie etc
however you set up a swaybar, it will always lift a wheel sooner than no swaybar. You cannot prevent them from applying a lifting force to the wheel that is in droop, and resisting compression on the other side. That is exactly what they are designed to do.
I will take some photos and measurements between the standard sway bar with extended links and currie sway bar to also share with you what I have seen, the difference between one restricting full suspension droop and the other maxing out standard patrol suspension geometry to the point where a 4 link would be better for the rear.

Basically what I have found for any thing other then up a ramp, the use of the rear sway bar helps to level the rear and assist the front to gain traction. My vehicle set up differs from the next and so forth. Really to gain any relevant information a number of different vehicles using the same ramp would need to be tested to gain an average comparison for any factual information.Re read your post HRD but believe your results are not a definitive finding, as I stated before a lot more comes into play to get your suspension working at its best.
 

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Discussion Starter · #13 · (Edited)
the conventional wisdom that a rear swaybar helps the front end flex better is generally referring to stock swaybar arrangements, not special custom Currie setups, so it's not really relevant to the discussion. And the quote of mine in your post is related to a stock swaybar as well - CrazyTrolling said he bets my swaybar is not setup correctly.

Also nothing in your post about making the front work better, and nothing in there contradicts the general principles of how a swaybar applies forces through the suspension. The fact that your custom currie swaybar setup doesn't limit your flex has nothing to do with whether they make the front work better or how swaybars work. But I see you also found normal swaybars only restricted your suspension movement, just like I did.

And your concern about on road handling without a rear swaybar is easily overcome with disconnects, obviously. But I have run without the stock rear swaybar on my LWB wagon before without any problems. Certainly didn't handle like a pig, but it's only 2" and 33s, not 5" and 37s.
 

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You need to think about the entire suspension at once, not just the one wheel that's at full extension with very little ground pressure. The swaybar is basically a torsion bar that connects both ends of he axle together, and yes as Mal stated correctly it's there to control the body in relation to the angle of the axle. So if the torsion bar was 100% rigid and did not flex at all you'd effectively be doubling the spring rate of the coil under compression, (we know torsion bar rates aren't close to this) anyway, so now you've got your rear swaybar retained and for example your left rear wheel droops down into a hole, the further it goes. The more is twists the torsion bar, the greater the spring rate on the opposing side of the axle, this gives increased ground pressure to the tyre that 9 times out of ten has the best traction. You also need to consider the inherent roll stiffness a standard radius arm front end has, and compare that to the flexibility of a std 5 link rear end, it's better to limit the rear in some respecs to equal things out. Say your arse falls into a big hole, no swaybars and your body will lean over in that direction, possibly over flexing the front end, lifting a wheel and breaking traction. Keeping the body flatter at all times increases ground pressure at all four corners.

The effectiveness of a swaybar cannot be measured using measurements of static position. It's not about who can flex the most it's about how each individual component works together to achieve optimal all round performance. Yes there's always certain situations where disconnecting swaybars momentarily may be benifical. But the benefits of retaining the rear swaybar at all times easily outweighs this. To be honest with a very very mild set up like yours I doubt suttle changes like "20mm more flex" would make much difference at all. So when people say it makes the front end "work better" or "flex better" it might not purely be referring to increased travel.
 

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Discussion Starter · #17 ·
You need to think about the entire suspension at once, not just the one wheel that's at full extension with very little ground pressure. The swaybar is basically a torsion bar that connects both ends of he axle together, and yes as Mal stated correctly it's there to control the body in relation to the angle of the axle. So if the torsion bar was 100% rigid and did not flex at all you'd effectively be doubling the spring rate of the coil under compression, (we know torsion bar rates aren't close to this)
this is totally unrealated to the discussion, but if the torsion bar was 100% rigid and did not flex at all, neither would your rear suspension. To double the spring rate of the coil under compression, you'd need a sway bar with the same rate as the coil spring. Remembering your sage advice to think of the entire system at once, this sway bar would also lift up the extended wheel with the same amount of force that it's pushing down on the compessed side...

anyway, so now you've got your rear swaybar retained and for example your left rear wheel droops down into a hole, the further it goes. The more is twists the torsion bar, the greater the spring rate on the opposing side of the axle, this gives increased ground pressure to the tyre that 9 times out of ten has the best traction.
again, nothing to do with the discussion about whether rear swaybars help front flex, but to respond to this... the left rear going into the hole will also not go as far into the hole because the swaybar is exerting a force against it. So the wheel with less traction will have even less less traction :p Now, LSD's work less effectively the less traction there is on the unloaded axle. So if you have an LSD, this is bad. If you have lockers, the amount of torque transmitted to each axle is limited by the axle with the most traction, so it doesn't matter. But like I said, this is nothing to do with what the thread's about.


You also need to consider the inherent roll stiffness a standard radius arm front end has, and compare that to the flexibility of a std 5 link rear end, it's better to limit the rear in some respecs to equal things out. Say your arse falls into a big hole, no swaybars and your body will lean over in that direction, possibly over flexing the front end, lifting a wheel and breaking traction. Keeping the body flatter at all times increases ground pressure at all four corners.
hypothetical situation and the problem with it is that real world measurements here disagree with what you imagine will happen. With the swaybar off, I get more front flex and more rear flex. So I'll be less likely to lift a wheel and break traction without the swaybar.

The effectiveness of a swaybar cannot be measured using measurements of static position. It's not about who can flex the most it's about how each individual component works together to achieve optimal all round performance. Yes there's always certain situations where disconnecting swaybars momentarily may be benifical.
enlighten us then - if there is a better way to test if a rear swaybar helps the front flex than to compress one rear corner, I'm all ears...

But the benefits of retaining the rear swaybar at all times easily outweighs this. To be honest with a very very mild set up like yours I doubt suttle changes like "20mm more flex" would make much difference at all.
except that it's 35mm front axle flex and 54mm rear axle flex. 1 1/3" front and 2 1/8" rear. Pretty significant differences for a vehicle with just 2" lift in my books!
 

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I should of stuck to my initial thoughts and ignored your thread all together, this like all your other "discussions" are simply a one eyed statement of your undisputed facts, with all responses disreguared as off topic and irellevent, or your choose to wit out an elaborate alternate theory to directly counter other opinions.

Bigger is not always better!
 

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Discussion Starter · #20 ·
What are you saying? You disagree that a sway bar lifts the extended wheel? Please explain how.

There is one thing I neglected to address in your extremely long post.
You also need to consider the inherent roll stiffness a standard radius arm front end has, and compare that to the flexibility of a std 5 link rear end, it's better to limit the rear in some respecs to equal things out
If you read my initial post, you'd see that with the swaybar off I get both the front and back to the bump stops. So why do I need to limit the rear to try and improve front flex? And You would also have seen that when i do limit rear, i also get less front flex, not more like you expect.
 
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