Factory Sway Bar Install

[ntsqd]

Adding pre-load to the sway-bar is an old trick used by "Ego-Challenge" circle track racers. This is where you get to take your street car out for several solo hot laps, one of which is timed. Adding pre-load or bias or whatever you want to call it with the sway-bar helps the car turn one direction only by increasing the effective spring rate on one side by lowering it on the other. Generally not something you want to do with a vehicle that has to turn both directions.

Late 60's - early 70"s GM A Body cars used an extremely similar mounting method for their optional rear sway-bars where the bar is attached only to the lower control arms.

The way to look at sway-bars in terms of handling is to realize that the axle with the stiffest roll-rate (sway-bar) will have the least cornering traction; it will be the first to break loose and slide. This is regardless of what both roll-rates are, they both could be really high or really low, which ever is the relatively stiffer axle will slide first.
It is typical in the U.S. for the front to have the higher roll-stiffness because Under-Steer is considered to be safer for the average American Driver than is Over-Steer.

 

[chuck]

I am a hunt and peck typer so type as few words as possible so don't always mae myself clear If you have doubt about the C bushings stiffening up the front ramp a eb with rubber bushings then change the bushings to poly and ramp it again. The one I did went from 900 rti to 440 rti. no other changes. When the EB came with rubber bushings they had no lean problem, I think they self adjusted by driving them around the block. The poly bushings are so stiff and tight they almost never self correct. The stock rear springs are too stiff so make a hard ride but not a sway problem. All the softer springs give a better ride but add sway. So when you change a stock EB to poly bushing in the front and soft springs in the rear the rear gets more sway and the front gets less. So the reason I think the rear sway bar gets more bang for the buck, not that a front bar does not work.

 

[ntsqd]

What's needed is a rubber C bushing with Caster correction built into it. I've some thots on how to make this work that I'll share if a vendor is interested in it.

 

[DirtDonk]

Yep. But also with some sort of built-in retention shoulder to keep them in place under hard use.
The old ones would stay in under "most" circumstances, but racers and hardcore off-roaders ran afoul of their tendency to spit out the sides when least desired.

Paul

 

[blubuckaroo]

There's always the other way to correct caster. Cutting and rewelding axle flanges is a process that can make a newbie shudder, but that's the best way. Your pinion angles stay correct too.

 

[ntsqd]

Cut & turn is the most ideal, but not always reasonable or even possible.

I think that I have a method that would anchor them fairly solidly.

 

[blubuckaroo]

Cut & turn is the most ideal, but not always reasonable or even possible.

I think that I have a method that would anchor them fairly solidly.

Did you eliminate the "C" altogether?

 

[ntsqd]

No, I did not.

 

[brianstrange]

Late to the post..... I'm having difficulty seeing the stock front assembly (Axle Poly C bushings and radius arms) as a virtual sway bar. That assembly offers no spring value by itself. I know when my front end is supported by the frame while in the air, the axle actuates against each other. I installed my Addco sway bar tonight, and jacking up one side of the axle pulls the other side with it (to a certain extent.) This bar mounts across the axle, and to the frame. I can see this happening with the factory bar too, but with less reaction. Even though the radius arms move, and the assembly holds the general shape of a sway bar, it is missing the bi-directional spring value that helps bind the two sides together while in motion.

 

[ntsqd]

Look at the housing as a torsion bar because it does have a spring constant. See the radius arms as the arms or levers to twist the housing with. Pretty much anything that you can apply a twist to has a torsional spring constant. Some have a really, really high number; others have a very low number; still others can be anywhere in between. A 2.5"-3.0" thick walled tube is going to have a pretty high constant, but the C bushings allow a bit of compliance or delay in response - reducing the effective torsional constant considerably.

 

[brianstrange]

Look at the housing as a torsion bar because it does have a spring constant. See the radius arms as the arms or levers to twist the housing with. Pretty much anything that you can apply a twist to has a torsional spring constant. Some have a really, really high number; others have a very low number; still others can be anywhere in between.
The C bushings allow a bit of compliance or delay in response, but once they're exceeded (compressed enough) the system does behave in sway-bar fashion.

I get this, but isn't that a radial property? A sway bar is using torsion to balance the spring load across a plain, no?

 

[ntsqd]

It is a simple torsion bar spring. Can think of the inside end of the axle in a corner as fixed and the outboard end of the axle as applying a twisting force, a Moment if you want, when it tries to compress. That's not quite the whole truth, but it works to simplify how it works.

 

[brianstrange]

It is a simple torsion bar spring. Can think of the inside end of the axle in a corner as fixed and the outboard end of the axle as applying a twisting force, a Moment if you want, when it tries to compress. That's not quite the whole truth, but it works to simplify how it works.

Like I said, I'm not seeing it functioning that way, but maybe it's just me. I can say that the Addco sway bar was a giant improvement for street driving. I'm sure it takes a lot of articulation away though.

 

[ntsqd]

If you anchor one end of a bar and put a lever on the other end and apply a force on the far end of the lever, then it is a torsion spring, correct?

This is not really any different from that.

 

[broncodriver99]

Like I said, I'm not seeing it functioning that way, but maybe it's just me.

I agree with you.

I have had several D44s hanging from the radius arms without springs installed and there is little or no resistance when a downward force is applied to one side. I was measuring and leveling everything during suspension installs. If they are off side to side I go and stand on the hub of the high side and it droops no problem and evens up the way the wedges are seated in the bushings. If you jack up on the middle of the axle you can pretty easily pivot the axle by pushing down on one side(this is one reason I question some of the thinking when it comes to Bronco lean). I am sure there is a little torsional resistance once everything is bolted together but not much. I can see how the factory bar adds torsional resistance but it probably isn't as effective as an aftermarket frame mounted bar.

I am currently running a Hellwig bar up front and it does a good job. Very little roll in corners, but I have a stock setup that I am planning to swap in if I lower my Bronco back down just to see how much of a difference there is. I imagine it will work pretty well on a stock height Bronco, not sure how it would perform once things are lifted and the geometry is changed.


Wasn't this thread about a stock sway bar install?

 

[ntsqd]

You missed the part where I said: "The C bushings allow a bit of compliance or delay in response, but once they're exceeded (compressed enough) the system does behave in sway-bar fashion." C Bushes of different materials will have different amounts of deflection before they 'limit-out' and the system starts to behave as a torsion spring system. Even two different urethane bushings may exhibit different max deflections.

It really doesn't matter where or how the bar is installed. Roll Spring Rate is determined by two things, torsion bar diameter and lever length. Frame mount vs. radius arm mount is determined by other design factors like ease of manufacture, ease of install, ground clearance, exhaust clearance, drive-shaft clearance, etc.

Wasn't this thread about a stock sway bar install?

Like that matters on any forum once the initial Q has been mostly answered.

 

[chuck]

The stock sway bar goes across the axle to the radius arms. It does not mount to the frame at all so why did ford bother? My thought was to dampen the flex in the C bushings. Then the diff. between 440 and 900 on a RTI ramp just by changing the C bushings says it all for me. see post 22

 

[blubuckaroo]

That's important test info (post #22).
I guess it doesn't really matter if your car doesn't see much articulation, but the selling point of the Bronco in the first place was its superior articulating front suspension. Everyone else was using leaf springs in the front.
I think poly bushings were a giant step backward.
Someone really needs to come up with lipped rubber "C" bushings.

 

[brianstrange]

I agree with you.

I have had several D44s hanging from the radius arms without springs installed and there is little or no resistance when a downward force is applied to one side. I was measuring and leveling everything during suspension installs. If they are off side to side I go and stand on the hub of the high side and it droops no problem and evens up the way the wedges are seated in the bushings. If you jack up on the middle of the axle you can pretty easily pivot the axle by pushing down on one side(this is one reason I question some of the thinking when it comes to Bronco lean). I am sure there is a little torsional resistance once everything is bolted together but not much. I can see how the factory bar adds torsional resistance but it probably isn't as effective as an aftermarket frame mounted bar.

I am currently running a Hellwig bar up front and it does a good job. Very little roll in corners, but I have a stock setup that I am planning to swap in if I lower my Bronco back down just to see how much of a difference there is. I imagine it will work pretty well on a stock height Bronco, not sure how it would perform once things are lifted and the geometry is changed.


Wasn't this thread about a stock sway bar install?

I'm glad it's not just me ;D The stock sway bar operates within the axles operating movement, and in that design, it compromises by attaching it to the radius arms, just short of the frame. It still does work in the same manner as a frame mounted bar. In the stock design, the anchor point is variable. Although not ideal for street performance, it's a good compromise for street and off road. The bar itself is thicker, and that also adds to it service strength, based on its overall size. Either way, it works against itself the same way. It was explained to me that a sway bar is really just a spring, that transfers the travel across the axle. It raises the spring rate on one side, while lowering the spring rate of the other. The real purpose is so you can achieve limited roll in a turn, without sacrificing ride comfort.

 

[chuck]

I agree with all that.