Why we wobble

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Twizzy228

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Saw this on another forum, thought I'd share:

I read several Ram sites and I keep reading about the rear end "wagging" after a drop and ways to fix it that are just wasting people's time and money. I'm gonna try to straighten out some of the reasons, dispel some myths and hopefully help some people out.
The main thing I read is that it's only lowered trucks doing it.
WRONG. ALL panhard bar equipped vehicles do it. It's simple physics...there's no way out of it. When you tie a lateral bar to the frame and axle, as the suspension cycles up and down it causes the bar to swing in an arc which in turn causes the body to move side to side. Again, there's no way put of this...it happens on every single panhard equipped vehicle on the planet. A tire with a lot of sidewall will absorb some of the motion you feel but it's still there.

Off track but look at how the rear wheels on a lowered 4th Gen are moved to the front...that's because they're on link bars that also swing in an arc...

er-Control-Arms-2009-2012-Dodge-Ram-1500-4x2-4x4-7.jpg

Okay...back on track...

panhard_displacement.jpg


This is a 2009^ Ram 1500...a damned clean one at that.

reardiff.jpg


That is the stock geometry...notice the bar is parallel to the axle. This starts the suspension in a neutral position which is what you want. You'll feel less of the horizontal movement when driving with the bar like this.

Now if you drop the truck and wind up with this like the old Bell Tech kits...you start having issues.

ear-Panhard-Bar-2009-2012-Dodge-Ram-1500-4x2-4x4-3.jpg

With the bar unlevel as the truck moves vertically the arc the bar swings in has to come down to the point of level THEN down past level which exaggerates this "wagging" feeling. Factor in the shorter, stiffer tires most of us run with a drop and you really feel it then. Even an adjustable panhard isn't going to fix the issue in this case...the bar being out of level is a main part of the issue. Another part of the issue without the adjustable bar is the fact that the stock bar isn't the exact right length to begin with. I've never looked at a 4th Gen Ram at stock height where the wheels were exactly centered side to side. Factor in manufacturing differences and the amount will vary from truck to truck but it's always there. Depending on how far out your truck is from the factory...lowering it can exacerbate the issue and make the "wagging" really bad. If your rear end is pushed 1/2" or more to one side your truck isn't tracking straight down the highway, combine that with vertical movement causing lateral movement and here comes the "wagging"

OK...back on track. How do we fix it? The answer is, we don't. We simply get it into as good of shape as we can to where we don't notice it as much.
This is done with the drop bracket we're all familiar with.

This is a pic of my own truck with a ~5" rear drop, adjustable bar and drop bracket.

564387_3842718186124_1991026926_n.jpg


This is what everyone tells us "fixes" the issue, right? Wrong...notice the bar is still not level.
This is my truck now with ~6" drop...NOW the bar is level. This is the only pic I have but you can see what's going on.

1493279_10201584897363942_1345118563_n.jpg


It literally takes a 6" rear drop for these off-the-shelf parts to bring the bar into a level position. The standard 4" drop will have the bar at an unacceptable angle...period. Again if you combine a 4" drop with a stock bar, the rear end will be pushed over and exaggerate the "wag".
The adjustable bar will help the issue greatly but it will NOT get rid of it. Why? Because there's no way to 100% get rid of it with a panhard bar.
I see people talking about changing shocks, adding helper airbags, etc. This is just throwing away your money unless those are things you're adding for another reason.

If you have a 4" drop and want a level bar, you can always have a curved bar made. These are perfectly acceptable and you can probably have one fabbed up for less than the cost of an adjustable Spohn bar. There's not many pics of curved bars I could find but they've been used for decades on 4wd front suspensions. They're generally solid bar stock for strength but are super easy to fab up and get the main part of the bar level.

solid_bar.jpg


Any suspension shop could make this in a day, it's still adjustable to center your wheels side to side and would be a better option than the straight bar on a 2-5" rear drop.

If you want a true fix...it's called a Watts Link.

kpc-watts-link.jpg

Obviously a lot more work and there are no bolt on kits for our trucks but this is the only true fix for a link style suspension. The bellcrank mounted to the diff allows the bars to move equal to each other as the suspension cycles vertically...keeping the axle centered at all points in the suspension travel. I'm not getting into that here...

I know that's long winded but hopefully it explains some of the "why" to the questions I keep seeing. Also to clarify...cab configuration and/or model do NOT matter in the least. The basic layout is exactly the same from an Express crew cab to an R/T and everywhere in between.
 

Statcher1

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Thanks for posting man.


Sent from the Rocket in my Pocket
 

NYCruiser

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I have no intention on dropping my truck, but I just learned a lot about our suspension! Glad you shared that.
 
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Twizzy228

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Having just installed my 2/4 drop YESTERDAY, I wish I woulda known this sooner!
 

petesnchz

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Nice info, think I'm going to hold off on a drop till one of the drop manufacturers comes out with a more complete kit.


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NYCruiser

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Should post a link to this post to the Drop Manufacturers page.
 

Lhemi

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Great stuff! I see you've got the complete Spohn rear end set up! Looks sharp.
 

Lhemi

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Are you also running the Hellwig sway bar with adjustable end links?
 

audio1der

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Glad our weather has warmed up; I'm getting under the truck to measure tonight.
 

BlownGP

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I love UNBROKEN....Always pushing the envelope with these trucks
 

charonblk07

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Most performance modded I've seen.

I'd question that statement, he's done amazing appearance and suspension work, a great audio build, but he's only got a P1SC prochager on it. There are several other builds that have more performance work done, but that doesn't detract from the amazing job Richard's done to the truck, or that he made the subscription cover of Truckin'.
 

Gecko

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I'd question that statement, he's done amazing appearance and suspension work, a great audio build, but he's only got a P1SC prochager on it. There are several other builds that have more performance work done, but that doesn't detract from the amazing job Richard's done to the truck, or that he made the subscription cover of Truckin'.

That was a great article about his truck too. Looked awesome!
 

charonblk07

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I retract my previous statement, he's been talking with Arrington about an aluminum 426 with a 4.0L whipple or maggy.
 
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