Anti wrap bar raises rear

How long is it in relation to your front 1/2 of the leaf spring?
What angle is the upper portion of the anti wrap bar at ride height?
How much separation is there between the mounts on the axle end?
 
I'd be willing to bet the bar is shorter than front half and the leverage is causing the vehicle to rise.
 
Jody Treadway said:
How long is it in relation to your front 1/2 of the leaf spring?
What angle is the upper portion of the anti wrap bar at ride height?
How much separation is there between the mounts on the axle end?
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The separation distance between the mounts at the axle end doesn't matter if its a triangulated solid bar. Spread mounts are just for stiffness so the axle can't rotate, so unless you're having some really bad compliance problem where things are bending under load... You draw a straight line between the anti wrap front pivot and the axle housing, and nothing matters about the rear mount at all if its a fixed mount.

I would think the position of the front pivot versus the front leaf spring shackle position is probably the key here. I think that's what XJsavage is saying too. That is probably creating too much anti-squat. The height of the anti wrap bar front pivot versus the shackle height will affect that too, and the pivot height versus the axle housing center height i think.. I've never messed with anti wrap bars before but I'm looking at pictures and figuring out the geometry effects in my head. Like all suspension geometry, its just pivot locations and linkage lengths.

Sounds like you're creating a really interesting problem where the anti wrap bar is making the instant center move; that's really what I'm trying to say.

My vehicle dynamics is a little rusty, and then there's the whole "leaf spring" ugliness...
 
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The amount of separation would/could have an effect on the angle of the "upper". Obviously that combined with lift height will be a determining factor on a number of things.
Just clarifying my post. :)

I want to see a side shot of the bar as well as know the length of the bar as it relates to the front leaf spring mounting position.
 
Fabrik8 said:
The separation distance between the mounts at the axle end doesn't matter if its a triangulated solid bar. Spread mounts are just for stiffness so the axle can't rotate, so unless you're having some really bad compliance problem where things are bending under load... You draw a straight line between the anti wrap front pivot and the axle housing, and nothing matters about the rear mount at all if its a fixed mount.

I would think the position of the front pivot versus the front leaf spring shackle position is probably the key here. I think that's what XJsavage is saying too. That is probably creating too much anti-squat. The height of the anti wrap bar front pivot versus the shackle height will affect that too, and the pivot height versus the axle housing center height i think.. I've never messed with anti wrap bars before but I'm looking at pictures and figuring out the geometry effects in my head. Like all suspension geometry, its just pivot locations and linkage lengths.

Sounds like you're creating a really interesting problem where the anti wrap bar is making the instant center move; that's really what I'm trying to say.

My vehicle dynamics is a little rusty, and then there's the whole "leaf spring" ugliness...
Click to expand...

You are likely on the right path. Antiwrap bars with leafs aren't as simple to figure as a traditional link suspension. Part of it depends on what type of wrap bar he has. I would guess it has 2 mounting positions at the axle and a single mount on the frame side, with a vertical shackle between the bar and mount.

Here is a quote from Pirate that talks about ladder bars.
Gordon said:
Here's the skinny. on a muscle car leaf spring rear the rule of thumb is that the instant center is located on a line through the center of the axle parallel to the ground. and it is 2/5 of the total leaf spring length in front of the axle. This works OK with smallish tires and flat leaf springs but it isn't very close at all with typical lifted 4x4. When I was in college I wrote a TK Solver program that calculated instant center location for leaf spring vehicles using the whole spring compliance. I don't really know how accurate that was either, but the first rule of thumb, that the instant center was always about the height of the axle center line seemed to hold true pretty well for the examples I tried.

Anyway with the Sam's Offroad style traction bar where the traction bar is bolted solid to the axle housing and then mounted to a shackle the traction bar its self is not the link at all the shackle is the link. So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.So if you draw a line through the upper and lower shackle bolts and a horizontal line through the axle center line where those lines intersect should be your instant center for your application.

Hope that helps
Click to expand...

As others said, the longer you can make it, the better you are, but axle separation is all about strength vs geometry in this instance.
 
Yall are adding too much BS to what should be a simple solution. Put a shackles as close to the the front u joint as possible without getting into any clearance issues and take into consideration enough distance that the shackle cannot hit the transfer case in the event of a leafspring failure. The bar should be pulling up on the shackle in tension and make the bar twice as strong as you think it needs to be.
I can't load any pics but maybe upnover can chime in with a pic of his for an example.
 
I think the term is pre load for what you have created.

But:
1) Its late
2) Ive been drunking
3) Fabirk8 is covering the book smarts
4) Jody is covering the practical real world application
 
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