Homemade Ladder Bars and Handling

I built a pair of homemade ladder bars based on a pair of four bar brackets welded under the axle housing in my highboy A. I think I screwed up. I think I've finally figured out a suspension induced handling problem. No pics to show.
Please call me out and describe why.
I believe that with a long lower connecting point of the ladder bar not being level is a cause of wheelbase change when the chassis is rolled left to right.
The rear wheelbase of my car changes more than 1/4" at one side of both based on body and chassis roll.
Dirt late model chassis guys do this with bar placement to induce a car WANTING to turn into a corner.
The wheelbase change makes the car want to bobble as the steering wheel makes no difference. The road makes the difference. It's a bear to read the road to know how the car is going to deal with it.
Pitman, Dean Lowe, ElPolacko, anybody chassis smart, please call me out on what I did wrong. I think I finally pictured why in my mind.
If a long triangle, the forward pivot point should be at the same level as the center of the upper and lower pickup points if the lower bar is not level.
The bars are NOT mounted parallel to chassis centerline.
Insight please.

 

Probably not going to get much help without the pics and a quarter inch doesn't sound like much. I'd think even on parallel leaf setups in a lean, there would be at least that much difference by flattening of the spring. Might have more to do with panhard bar geometry (assuming you have one).

 

1/4" at each side will get your full and undivided attention at 70 mph when you're beside an 18 wheeler. A panhard bar is a necessity and geometry on that may part of the problem.
My ladder bars mount below the axle housing for both the upper and lower tubes. My rethinking leads me to believe the upper and lower need to be evenly spaced above and below the axle tubes to prevent rear steer,, or with my setup, the lower bar needs to be level.
Gettin' ready for work.

 

In a ladder bar setup the layout of the upper and lower bars decide nothing.
You can make them like a corkscrew if you like.
The deciding factor for handling issues is location of the pivot points at the front...basicly in side view BUT also in looking down (or up).

 

Look at a Pete & Jakes or similar setup. They work!

 

Hacker and bang, all correct statements. There's something to what I built that's just not exactly right. I built the suspension using only bought four bar brackets, coil over shocks, and heims.
It has to do with O < O, being pivot point, upper and lower bar placement, axle tube placement. Left O to be of forward of the car and suspension.
If < is placed too low or at incorrect angle, it will induce rear steer. Rear steer will make a hotrod type car look like a bobble head.

 

I'm really failing to see how a ladder bar will induce rear steer unless the rear axle is moving side to side. That would make me believe it is a problem with the panhard bar. I assume you have one. If you have a short one it will move the axle to the side in a bump, more so if it is angled up or down at ride height. I know a lot of kits mount the panhard to the pumpkin but I'm not a fan of those, longer is better. I know I fixed a OT pro street car years ago that was squirrly in the back by changing out a short (12") panhard bar to a longer one.

 

Hard to say whats going on without some pics of your set-up , But I am also wondering if you have a panhard bar pulling/pushing the rear end sideways...





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I'm with some others. Not nearly as important as it is on a 4-link setup. And I'm pretty sure if the bars have some decent length to them and are triangulated, you should not have any kind of rear steer issue, assuming the rear isn't pitching side to side (needing a panhard bar).

 

I am with the others as the problem might be with the panhard bar. How long is it? Are the pivot points on the panhard bar relatively level to each other? You could conduct a test by measuring a reference point from the from the top of the axle housing to a given point on the frame at ride height. Jack the car up and set the frame on jack stands, remove or disconnect both C/O rear shocks. With a floor jack under the rearend, set the axle height back to your ride height reference point. Now raise and lower the axle and check the side movement of the rear axle with a tape measure or some sort of a guage. I would check it at 2" extension and 2" compression of of ride height. This is the best way I know of telling what is changing when the suspension is in it's cycle.

 

Keep in mind that I've built ladder bars since this pic and have cut my hair some.
The panhard is about 18" at centers. It's still about as level as in this pic. It mimics the store bought piece that attaches with two of the diff housing studs to a point.
More pics later as time allows.

 

the problem could be the place you have the fronts mounted. I bet you are getting some flex there

 

Your build description is so hard to follow that I'm not going to comment as to what to do there. A photo of what you actually built would help a lot,,,,I think. I've done a fair amount of Chassis builds and several Ladder Bar systems. I've never had a rear end steer a car at speed on the flat or strait ahead. If your car is getting Krazzy while at 70 passing a Tuck I'd be looking at the Front end, not the rear. Sounds to me like your picking on the only thing you hand built just because you didn't understand how it should work. I have cured a few problems in the past for people that started out sounding a bit like your issue. All of them have been in the front, not the rear. I large issue people don't get is Polly shackle bushings. You can't lock them down tight. Most don't fit right when new. Tight king pins is another common steers itself problem. To tight gear box another common issue with self steering cars. Ladder Bars locked in place on the frame and rear axle should not steer the car.
The Wizzard

 

I take it you removed what looks to be a 3 link setup and built ladderbars to replace them?
Panhard bar isn't the perfect setup but like you say, they sell them that way and it probably isn't causing enough rear steer to be real noticeable. If you mounted the ladderbars where the lower bars are attached to the frame I'm with 49ratfink. Hard to tell from the pic but there is enough leverage going on there with that much drop to flex that crossmember but then can't really tell how stout the crossmember is in the pic. You might need to add some triangulated bars from the frame to the c/m near where the mounts are.
Dumb questain but when you changed to ladderbars you did take the upper bar out didn't you?

 

PNB, you're on the same track of questions in my mind. I do have poly shackle bushings and have backed off on nut tension. Dead perch, NOT THE FISH, is in consideration because I don't want to install a front panhard. I may be wrong with not wanting to as I don't have cross steering.
Flex at the forward mounts doesn't seem plausible to me because the curved bars you see in the pic attach to the box plates and to the tubes the bolts pass thru for the heims at the forward end. I think the gusseting should make for little flex.
The car does not drive like a truck with stuck kingpins. A truck with stuck kingpins will stay into the last mode of correctional steering and have a need to be given the next. The front will make the tail wag. Driven that problem and new stuck kingpins, due to installation problems, to know that situation very well.
I work at a truck and auto repair shop and do a lot of troubleshooting on drivabilility problems in cars to Kenworths. Ain't saying I know all the shit, but have a decent grasp of some of the smells.
The front may still be the problem to cause the rear to act incorrectly. I know pics and dimensions are some of the answer sources. Angle of the dangle may be the root of the problem.

 

Upper bar is out. It was used as a stationary to hold pinion angle to make the uppers of the ladder bars.
If it was still in,the suspension would not have ability to move unless something broke. Triangulation.

 

What happens when you walk over to the front of the Rig and put your body weight on the left frame horn and then go do the same on the right? Without cross steer you should not need a front sway bar however some like them. I do, but installed wrong they can cause a self steering issue of there own.
The Wizzard

 

The front left drops as equal as the front right. Yes, the steering wheel does show that bump steer exists. If bump steer was horrible, I'd be complaining of changing lanes with every verticle suspension movement.
PNB, along with your statement of not needing a front sway bar, it also goes along with my learning of a beam axle with split wishbones shouldn't need a front sway bar.
Thanks to all that are trying to help think through this. The Lord knows I'm trying.

 

What kind of steering box are you running?

 

Panhard bar doesn't look odd and ladder bars are just a lever of sorts. Pivot point to pivot point is what matters not the shape or where they mount, and those don't look extreme either (pic could be better). Problem could be further north, shackle angle too shallow loaded or bad draglink geometry?

 

A little Bump Steer you'll get used to. So just to rule out the front end I'd lift the front tires off the ground and put stands under the front axle. Then grab a tire and hand turn it lock to lock. You know it should be smooth and easy all the way stop to stop. If it is I would then go to the rear and get it up with stand under the frame and remove the springs and shocks. Start moving the rear housing up and down till is seen what was causing my dirty laundry.
The Wizzard

 

I ment to add that the Speedway replacement Vega style steering gears have issues. I have scraped 3 of them in the last 2 years.

 

Steering box Q. I pulled it out of a manual steer Maverick and had it freshened up in a very reputable shop in Dallas I use for big truck stuff. They do have some warranty stuff, but that problem is corrected as it's ugly head shows up. Many years of not dealing with a jack leg outfit.

Shackles look good with the car on the ground and drivable. The paint below the spring eyes isn't pounded off, which should indicate correct spring tension and shackle movement and good bushings. Minimal drag link geometry induced bump steer, OK, I know how to drove through it as it occurs.

 

I'd say you pretty much took the front end out of the Question. Good luck and let us know what you find. Sorry I couldn't help more.
The Wizzard

 

Forgive me, but are the shackles at or near 45 deg. at rest, or more straight up and down. I know it isn't cross steer but wonder if the axle may be wandering on you.

 

PNB, I appreciate your thought process and taking the time. I hope to be able do for you as well.

 

45 would be damn close and the question of the axle swinging under the shackles has been a large thought.
I also question why some folks can drive a car with a Ford style front axle for miles at speed on the same bad roads that upset my car. I will promise you that I can drive some worn out shit hard if all the geometry is correct and have done it for many a mile to get to work and go home on a twisted road 45 mile one way trip. Not that I would ever speed...............
From rumors abound, there's a steel 32 Tubor with a BBC out of Mississippi, that will make your mirror forget when a car that fast closes in and leaves you on the big road. What did I engineer into my experiment?

 

I'm out of ideas at the moment. Try to get more pics and someones bound to sort it out eventually.

 

So I didn't just log off and forget. Funny how a challange kind of takes over. So I will give you credit that it's not something as simple as low air in the tires. If it is in fact the rear end steering the car it should be connected to the rear panhard bar. How much up and down travel do you have in the back? What do you have for rear spring and shocks? We are assuming (I hate doing that) the only thing you changed at all is the ladder bars on the rear and that "nothing" else was done to anything on the chassis. Am I right?
The Wizzard

 

What diameter is your track rod ???