Rear suspension question.... 4 link or ladder bar?

on my 41 plymouth i have a set of compition enginering ladder bars on it. i was going to leave them and put a adjustable heim joint on the one end. but i think i may need a clevis or some kinda of other pivot at the axle end. they just bolt around the axle. i belive these are ment to be used in conjuction with the leaf springs. but since i have air ride im not so sure about them. i have a panhard bar in place all ready.

I can make the room in the floor for a 4 link but is it really worth it? if i put heim ends on the ladder bars will they still work properly and not bind? im very concerned with side to side binding. the ladder bars are 38" long. these are the only two pics i have of it right now. i all so planned on tacking the brackets to the axle just to make sure it wont slip.

These are older pics there is a lot more cross members and a panhard bar and shocks in place.

 

I know a lot of airbag guys use 4-bar setups, but i see no reason not to use ladder bars as long as you can cycle the setup without binding...

 

Other than pinion angle change and the arc the axle swings in with ladder bars, potentially stabbing the tranny with the driveshaft everytime you air out, ladder bars are fine with airbags.

 

Basically that makes it a 2 link.If it were me,I would go with a tri-4 link.The 2 link has a tendancy to bind on uneven surfaces.

 

Assuming this is a street vehicle,how does the body roll will parallel ladder bars ? The rear end will go up and down,but it doesn't want to roll.You've created a bind,because the axle won't twist.

And what takes the torque reaction,if the ladder bars are not welded to the rear end ?
Two bolts and a thin strap clamp isn't enough.

 

Not to mention, you mite want to plate that step notch since you didn't miter the joints.

 

These are my exact concerns. i was worrid about side to side roll...

ad the chassis isnt done yet every thing gets plated this is a older pic.

im just going to scrap this and put in a triangulated 4 link.

Thanks
Bryan

 

Good idea.

Few people ever ask themselves why Detroit never used parallel ladder bars.

 

What Ian said....but besides that...from the looks of what you have there, CE sure makes a crappy ladder bar!!!

 

If you're gonna scrap the ladder bars, send em my way...I could put them to good use on my '31 Plymouth...

 

That has to be the best way to put it. i wish i thought of that.

Suicidedoors.com has a real nice 4 link kit im going to purchase.

Thank you guys for your help.
Bryan

 

Suicidedoors.com has some really nice parts, and damned good prices...

 

not trying to be a smart ass,,cuz i am trying to learn,,but

isnt a parallel ladder bar pretty much the same thing as a 60's GM truck dual trailing arm rear suspension ???

it does the same thing as ladder bars? right?

i have heard of quite a few people using this type of set up.

 

Truck arms point inward like P&J ladder bars.

 

i was going to suggest the truck bars but i could not remember if there were upper links on those.

Now what does them being on a angle have to do with it. i assume it allows for more side to side twist like this.

 

Truck arms act more like a stock Ford wishbone,
or the Pete & Jake trailing arms.

 

Basically, ladder bars force the axle tubes to twist as a swar bar does. Only an axle tube won't twist for long, it will break. The tubes are only held in by spot welds. Even if the welds are strengthened, something will break.

As someone else alluded to, it is best to look to the OEMs for ideas, as they generally pay their engineers more than we get for our ideas...

Cosmo

 

the closer to a triangle, the better articulation you will have. they can be setup to give a lot of lift quite easily, and ride super smooth. they also work very well at putting the power to the pavement. perhaps best of all is the simplicity of the setup.

 

hence the use in nascar then eh

 

easy way to think about it is if you bend a paper clip into a U

the 2 legs = ladder bars or split wish bones
the flat between = rear axle

with your finger holding the 2 legs flat you can not pick up on just one side of what would be the rear axle.

if you bend the 2 legs in (like the truck arm set up) you can pick up one side with out the other side moving up.

 

Truck arm suspensions are great if setup properly to allow for articulation...a NASCAR style setup isn't ideal for street use, they don't have squat for body roll or articulation...

 

if your suspension is fighting body roll, there is something wrong with your suspension. that is up to the springs, shocks and/or a sway bar.

and as far as articulation, the nature of long triangulated links makes them articulate like crazy. you'd have to be a moron to build a truck arm setup that binds.

you say not ideal for the street, i direct you to the comment above, why didn't detroit use them? they did.

 

I meant copying a NASCAR suspension for street use, truck arm suspensions are great for the street, but the angles and spring rates used in NASCAR would be useless in the real world...just because it works on a drag or circle track car people think they can put it on the street...the style may be the same, but the geometry isn't

 

do you guys use the actual truck trailing arms ? or make your own arm setups?

 

I've used '67-'72 chevy truck arms, made my own replacements and made custom ones...my '31 Plymouth was going to get some, but decided to go with triangulated ladder bars...

 

What about hair pins? Do they flex enough not to bind? Can you triangulate them somewhat?

 

That's 'cause in a pavement stock car they run huge anti-roll bars to force the car to corner flat. Gotta use all four tires, doncha know.

Pick your spring rates according to what your auto weighs on that end and truck arms will serve you well. You will need a panhard bar (stock car guys call it a track bar) though, to locate the rear end laterally.

 

check out air ride technoligies, no so i know i butchered up the spelling but you know what im talkin about, they have some great tech stuff on what to use and not use with air ride stuff. i used there triangular 4 link set up on a truck im building nice quiality stuff. just my .02

 

heres a pic of there setup

 

your splittin hairs. truck arm/nascar is describing the general concept used here, not necessarily the actual parts. as far as spring rates, we're talkin airbag suspensions anyways. nobody here is talking about using the high rate coils.

Sam, i made my own arms, in my case it's a ground scrapin sled, i looked into the actual truck arms but figured there wasn't much difference in labor and cost to just make my own. IIRC i used 2x3 box tubing. i should note probably the biggest drawback to this setup is exhaust clearance, gotta make sure you leave room between the front mounts for the pipes.

some old build pics: