I dare to differ with you because the radius-rods did indeed smooth out the ride on both my Excursions, and a similar product did the same for another leaf-sprung vehicle I owned years ago. I know it was the radius-rods because the abrupt improvement occurred when I installed them alone ... no other mods were installed at the same time.

Dampeners (typical automotive shock absorbers) are good for vertical dampening. I tend to think the reverberation I felt was the result of the axle wanting to move forward and rearward ... small amount of spring wrap ... and pinning the axle in a controlled arc with the rods stopped it.

Like the X, my F150 has lift blocks between the leaves and axle, so the opportunity for spring wrap exists.

 

You are not differing with me, you are differing with basic physics.
But if your rods make you happy then by all means run em, lord knows you paid good money for them. Might as well insist they are doing what you want them to.

 

Nope, not differing with physics, but employing physical controls. One cannot argue with or alter the laws of physics. However, by limiting rear axle travel to a controlled arc, the shock absorbers can then perform their function vertically without longitudinal axle movement.

And yeah, the money I paid for them (twice) was money well spent. The return on investment resulted in many more smiles per gallon.

 

the factory Excursion anti wrap bar does an adequate job of controlling axle wrap under hard acceleration,

A fixed beam style traction bar such as the landyot has the added benifit of controlling axle wrap under extreme braking such as happens during a panic stop.

Railroad tracks, potholes and road surfaces do not cause axle wrap. Torque causes axle wrap.

Where I question the landyots design is how it allows or as is the case doesn't allow the length to change. A proper fixed end traction bar needs a shackle to allow the length to change as the spring goes from Arched to Flat.

What is see in the landot is it keeps the front half of the spring in a tensioned 1/2 arch and could possibly even cause the spring to bend if you had enough spring travel. How this can possibly smooth out the ride,stop reverberations or alter how the show works I am uncertain since traction bars are not known to do any of those things.


Here is somebody homemade traction bar with a shackle to allow the spring length to change.

 

A better look at a shackle end on a anti wrap bar setup

 

And the landyot.

Where is the provision for the change is spring length ?

 

Since the original question was has anybody stepped up to make landyots.

Many companies make a anti wrap that will work on the excursion / super platform but here is a link to a company I know well and for $200 you get a proper design anti wrap bar.

Antiwrap/Traction Bar Complete Kit - RuffStuff Specialties

 

True, and that's the only time it functions. It's useless at all other times.

True, the radius-rods perform under acceleration AND braking.

True, axle torque while accelerating or braking causes spring wrap. But in addition, while proceeding in a steady motion (no accelerating or decelerating) and a rear wheel comes upon a resistance in the road surface ... pot hole, bump, railroad track, road kill ... that rear wheel is briefly decelerated by that resistance and imparts not torque, but a bending moment on the leaf spring which is amplified (mechanical advantage) by the extra distance the axle is located away from the leaf spring due to the lift blocks. That bending moment induces spring wrap, and when it occurs on only one rear wheel, it causes the rear axle to become out of square with the vehicle's centerline resulting in rear axle induced steering ... AKA: wandering.

If you look, you may witness International Harvester uses radius-rods on some of their large single-rear-axle trucks with leaf spring suspension.

 

let me see if I can unravel what is happening here.

first off, because the axle housing is solid and connected to leaf springs on both sides, if one side twist as in axle wrap then the other side must also twist. simply because the axle housing does not move independently from side to side. you can't have one spring twist and get shorter without the other side doing the same.

when a vehicle hits a obstacle with one wheel, be it a pot hole, rail road track or other wise what cause the vehicle to loose stability or "wander" is when it runs out of travel. as long as the suspension can move up it will absorb the impact and you will not rapidly shoot off in a unwanted different direction.

now, when a 1 wheel hits an obstacle and compresses the suspension it moves up in an arch and changes the length of the spring, if one wheel travels up and the other doesn't it does indeed put the axle out of square with the chassis. all leaf springs do this just by their design. however this is rarely ( at least in factory designed suspension enough to noticeably change the vehicle direction. if it was then i suspect all the leaf sprung cars ever produced would be crashed by now.

a leaf sprung suspension by its nature has a lot of movement in directions other then the perfect arch like created by a link suspension, while this isn't ideal it works on vehicle like trucks simply because they do not require precision handling. if like you imply, that movement resulted in wander then it would apply to all leaf spring suspensions and not just the excursion.

so what is happening with the landyot that seems to give it better handling when you hit an obstacle ? while i have not ever had the opportunity to study one in person and cycle the suspension it appears to me that by affixing the rod to the front of the spring and the axle without a shackle to let the spring get longer as it flattens out that it is binding the spring when it compresses. by binding the spring you are increasing the effective spring rate and that is likely just enough to keep the suspension from bottoming out and "wander" or dart off in an undesired direction.

as far as curing the notorious excursion wander however, most people experience the wander simply cruising down a smooth highway where the suspension is not being cycled and the cause of that wander is typically worn out parts and a lack of caster from the sagged springs.

I would propose that a more ideal way to keep the excursion from darting around or wandering when you hit an obstacle is to increase the suspension travel and or increase the compression valving on the shocks not by binding up the precious little travel the excursion has.

 

here is one of the rigs I built back in the day, it had about 36' of wheel travel and some wicked rear steer due to the link geometry. but even with that much rear steer it was stable at speed when one rear tire hit a big whoop. it just sucked it up and keep going straight ahead.... bottom out one or more wheels and its anybody guess where you are going to land, usually on the roof.

 

another rig I built for my wife and due to possibly a few to many beers the night I welded in the rear spring perches the axle was out of square maybe an inch. one the road it would crab a little bit but honestly you could not really tell when driving it. a rear axle out of square on a truck is hard on the tires but you would be surprised at how many leaf spring trucks on the road are out of square. it isn't the end of the world.

 

heres the pic i was looking for,
even with that crazy amount of rear steer this rig was perfectly stable bombing down rutted , pot hole, whooped roads at 70 mph. the rear steer did not cause it to wander.

 

after building several rigs from the ground up including designing the suspension I eventually got pretty good at it, built this one and the suspension was spot on, but it wandered all over the damn place just driving down a smooth road. could not keep it straight. it was a like a drunk Excursion on prom night.

turns out I screwed up the front caster when put the tubes and knuckles on the axle.
dialed in the caster and she was rock steady at 100+ mph over rough terrain.

 

Pirate-I did not want to quote your entire post but concerning radius rods... the front end of the rod has 2 connector plates welded to the bottom of the front shackle of the rear leaf spring. The front part of the rod is attached between the plates with a bolt through the front part of the rod which has a plastic bushing inside. Therefore the front part does rotate to accomodate vertical forces on the springs. The rear part has a 2 part clamp that encircles the axle. It has welded to it on the front, a bracket with a hole by which the rod connects to rear bracket. A bolt threaded into the rod is attached to this rear bracket with nuts,locking nuts and thick rubber bushings on either side of the rear bracket . The bushing compresses to accomodate horizontal (albeit limited) movement. Independent rear suspensions work off of a fixed attachment of the traveling strut to the frame with accomodation of vertical movement by coil springs. Other than the bushings in the strut attachments, that mounting allows for, no rotational movement of the axles occurs that I am aware of. Essentially the axles themselves stay perpendicular to the long axis of the vehicle. The attachment of the X's axle is by way of weak, over flexing springs (for soccer moms to have a softer ride) attached a couple of inches above the axle itself. As you know, they are so puny, blocks had to be used to raise the rear of the vehicle to a level position. Every horizontal movement, which is allowed by way of spring wrap on one side is translated into an equal and opposite reaction on the other side, thus the axle is no longer perpendicular to the long axis of the vehicle..ergo you change directions. Ford's addition of the snubber bar to later models of the Excursion bears witness to their recognition that spring wrap is an issue. IMHO, the snubber bar is an absolute joke.

With that said, the radius rods are effective in preventing rear steer when one hits a significant bump or pothole. Does that movement produce a significant amount of force to cause wander going down a reasonably smooth highway in and of itself--I would say "No". I can bear witness to this from personal experience with 3 sets of radius rods. My first X was 2WD so I had independent front suspension. It would jump big time when I hit a pothole or bump. The radius rods eliminated that and made a dramatic difference in driveability. With these 4WDs, the front can't stay on track and the rear end kicks in under certain conditions and makes it worse. I believe your alignment theory involving caster is spot on. I also believe the front suspension itself needs to be heavier duty.

I'm not sure why I wrote all this except for the search for answers to another puzzling problem in life. The fun is exchanging ideas in the endeavor for solutions. Also, we are all nuts! Does your average sane person write dissertations on a forum concerning 11 to 16 year old SUV's??

BTW, those are some biatching rides you've made!

 

I think for this discussion we should clarify the terms.

Wander is the tendency of the vehicle to drift off line from the direction it is being steered by the driver, this is typically driving down a smooth-ish road or highway in a straight line

and completely separate handling straight is "bucking" or darting off course when you hit an obstacle such as a pot hole.

both watcher and cficare make some correct and good points but lets see if I can steer ( pun intended) the some misconceptions in a diffrent direction.

Wander and "rear steer"
I totally get what you guys are saying and on the surface I can see how it would make sense that when the rear axle articulates and becomes out of square with the chassis it would cause the vehicle to change direction. however this just is not the case. I will attach some pic after this post.. having driven several vehicles that actually have a steerable rear axle that is independently controlled by the operator and independent from the front axles operation I can tell you that what actually happens is the vehicle will crab not change directions or wander around and it will not "BUCK" or "Dart" off course suddenly. it just grabs down the road. you have probably seen trucks ( including semi's ) that are crabing due to an axle out of alignment or bent. I have driven many vehicles with bent rear axles that are not perpendicular. and even zig zagging the rear axle while going straight forward the vehicle doesn't wander or turn, it just crabs.

Buck or Dart.
I covered this in the above post but will expand on the Excursions specific issue. to reiterate thought. the sudden change in direction from hitting a obstacle is a result of bottoming out. with the suspension compressing it is absorbing energy and soon released in a controlled manner when the suspension rebounds., when the suspension bottoms out it can no longer absorb energy but if you hit something hard enough and there is still more energy then the suspension can absorb that energy has to go somewhere, that somewhere is into the chassis and it reacts by Bucking or being kicked in the direction the energy it traveling. the reason the Excursion is prone to this is not due to "weak" or "overly flexY' springs. in fact the Excursion has the SAME spring rate as the F250 springs everybody like to swap into the excursion. the difference is the Excursion has about 5' of arch or travel and the F250 spring has about 8' but the springs are the same spring rate or flexyness. the F250 spring has more travel and can therefore absorb more energy before it bottoms out. but once it does bottom out it will behave exactly in the same manner as the Excursion spring.

for simplification the front springs are the same issue, they do not need to be more "heavy duty" or in technical terms have a higher spring rate. the spring rates are correct. the fronts just like the rear sufferers from a lack of travel.

it should be noted that the Excursions limited travel is made worse by the actual spring design. the low arch ( which establishes the amount of travel ) means the spring is nearly flat at ride height. this is an issue because leaf springs sag more rapidly when they are flat rather then arched and are quickly ruined when they are flexed into a negative arch ( something you see frequently on a stock excursion and usually accompanied by blown out bomb stops ) there is a process in leaf spring manufacturing called Bulldozing and it is an attempt to minimize a flat to negative leaf spring from losing its temper and sagging. I have seen fords actual blueprints and technical notes on the Excursion spring and it clearly states they are to be Bulldozed so we know for a fact Ford was aware of the problem before we the consumer ever even owned them.

lets go back to the radius rod.
while I have not played with a set in the shop or had the oppertunity to cycle a suspension to study them first hand watchers description is mostly right on. however we still need to get down to what exactly makes them able to provide the benefits you guys have experienced. While i recognize your theory it just doesn't pan out as I have tried to explain above. further more. looking at them right now I can tell you that with the radius rods attached the axle still travel is a arc and by default the arc will cause a change in wheelbase...cause rear steer as you guys describe. , the difference is that the axle is now being forced to follow the arc of the landyot rod but also fighting to follow the arc that the spring wants it to swing on. that brings us back to binding. if the axle is trying to follow 2 different arcs then that is butting the spring is a bound state which like I said will increase its effective spring rate, apparently just enough to keep it from bottoming out on smaller obstacles.

if that is or has worked out for how you use your excursion and it eliminates the Bucking or darting then great, run em. id suggest that more travel is a better option but hey. to each their own. as far as curing the traditional excursion "WANDER" no way no how. that is a front end issue from worn out parts or lack of caster.

pics of a rear steer crab coming up.....