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Traction Bars: A closer look

34K views 47 replies 13 participants last post by  CamTom12 
#1 ·
This thread was started from another thread that got way off track and end up speaking more about the effects of various designs and style of traction bars on travel, articulation, strength, etc...

TO not end up having to rehash a lot of what has already been posted but to still have it all in one place I am coping over all the relevant posts as quotes in the next post of two. Its improvident to understand that much of the references made initially are about the DPP bars which I will have pictures posted of so you can see them.

Anything and everything dealing with traction bars effects and designs is fair topic here. The idea is to help people see the limits of various designs and possibly figure out what possibilities exist based on what the end user has planned for their truck: Pulling, Towing, 1/4 mile track, light off road, extreme off road.

I may go and pull some info from some other threads were good info was posted about the effects of travel on flex and binding.

What happened that got off on this topic was the effects certain styles of traction bars have specifically on binding when actual articulation takes place ( not even travel) where one wheel goes up to full compression and also inward and the other goes down to full droop and outward.

I am going to be posting the quoted info and pics in the very next thread to bring this up to speed.
 
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#2 ·
The actual traction bars that started the discussion and we are referencing are these by DDP

It should be noted that a change was made to the front mount where it now wraps around the frame and allows for 2 more bolts from the side as well so its beefed up considerably.









Do you guys realize that if you weld one of these ladder bars to each side of your axle that it can no longer articulate ?

Ie: drive one tire of the axle onto a curb and either the other tire is going to hang in the air or your frame will twist/bend or the mount/bolts will break or the axle will twist or break or ???? Something has to give.

I suspect this is what the bolt breaking was all about.

A certain air suspension works similar to this. It will and has broken axle tubes.

A non articulating axle might be OK for sled pulling. I wouldn't use them on the street though.

There is absolutely no need for a sway bar with that setup. There is no way the frame can lean over the axle unless you twist it.
I dont know a whole lot on the subject but I believe that is what the shackles does. It will allow the suspension to flex. I am sure that someone else with experience will chime in
The shackle will allow the axle to follow the arc of the spring as it compresses. But it won't allow the axle to articulate, unless it forces one side back and the other forward against the will of the leaf spring.

If someone has one of these installed, drive one rear tire up on a curb and take pictures. Something somewhere has to flex to allow the axle to articulate - if it does.

If you want the axle to articulate, I recommend mounting the ladder bar to 2 large bushings, like the front axle of an 08+ SD does.
the shackle will work the same way as the shackle on the leaf springs one will go forward and one will go backwards so that it will articulate
I'd like to see a picture of that.

I'd like you to tell me how much force it takes to lengthen a leaf spring on one side of the truck and shorten the one on the other side.

And, if that does allow the axle to articulate, its now not perpendicular to the frame. Can you say bump steer ?

Bolts don't shear easily. I suspect this is why there was a bolt/mount problem. Controlling the axle torque itself is fairly trivial. There has to be other forces at play to have mount/bolt problems.
Yes, it is called the bushing in the shackle will compress.
Yes, it will put a lateral twisting force on the bolts. The force is larger on lifted trucks (for that matter, a lot of little things become big problems on lifted trucks). But for most people, they don't need to worry about it.



The frame is meant to allow some twist. It was designed for it. I have it happen every morning and evening when I pull in and out of my driveway. I can watch in the mirror and see the body lines on the cab and bed move. The particular entrance angle of the driveway and the radius I have to turn to get in mean I have quite a bit of flex (and articulation) happening. But, it is all spread out between springs, bushings, and frame members that are meant to flex.
So even with the traction bars like these, unless you are putting them on a truck with several inches of lift, it won't be a problem.
So now these should be out and installed on a few trucks.

How are they working out?

Any of the issues that Me2 brought up?

How's the fit and quailty?

Do they allow the rear axle to fully travel and what about articulation ( one wheel up, one down? It looks like enough flex from the various bushing.
We only had few sets made the first round and they were all spoken for by some of our customers that I have no idea if they are even members of PSN. amarillo250 is the only one getting a set from the last batch that is a for sure member here. So soon as he gets his on I am sure you will all hear from him.

As far as the others, I have had no complaints from anyone and only good feedback. One guy was concerned they may rattle like some other brands apparently do but he has been happy.

Quality and fitment I consider to be top notch as I would not sale a piece of junk to my customers. But amarillo250 can speak for this once he gets his.

As for the articualtion question, the off road shops that I had look at these when we first built this design said they would be perfect for basic daily drivers and mild off roading and mildly lifted trucks. They did say they would most likely not be to good for major off roading and rock crawling.

I have a big rock that is about 16" tall out in front of the house and as soon as I get a minute I am going to go back one tire of my pulling truck on it and take some pictures.
That is what I figured looking at the design. It would be neat to test one out and see just how much travel it can go without binding up. You then could list a general range for people. Not like too many are having their trucks setup with 12"-20" of rear travel. More like under 10".
so about driving on that rock...... i can visualize the articulation issues. just wondering how much it has, or how much of a prob it would be. i think of it like, if you hold a hammer in your hand, with your arm straight, ( like the bar and shackle) and twist your arm, the hammer will twist to. if it dont twist, and you force it, it twists in your palm. what breaks or bends on the bars?? or will the bar itself "flex/twist" slightly to accomodate it? when i pull my trailer into/out of the field hauling round bales, some of the entrances twist/tweak me pretty good. i realize that you prolly cannot design change, but to buy your set to modify them, what would be the fix?
The bushings will allow for some of the twist.

If you wanted it to allow for full flex swap out all the joints for jonny joints and you will allow for full articulation. That is how I have seen a number of jeeps setup and those things have extreme travel and articulation. The other thing said was when setting up the traction bar was to set it to get eh shackle as close to 90 degrees to the bar as possible at ride height. As the bar was slightly differnet not sure if that is the case here but when you saw the travel it made sense.
so if he drove onthe rock, and took a pic looking down the bar like he was looking down the barrel of a gun, if would be seen whether or not there actually was enough twist to actually need to go that far. there a gorgeous bar, just trying to make a informed decision. its as i said, im one of the cases where extreme "twist" comes into play, and dont wanna get a set to have them bend, or radically accelerate wear on the bushings, and have to keep buying bushings. wouldnt be cost effective.
You are totally missing the point on what is limiting the articulation.

Jeeps do use Johny Joints and they do allow more articulation, but for very different reasons.
dont stop there, this is usually the part where you explain......
I was speaking about it from the twisting of the articulation. I saw it that the jonny joints would allow more twist without bind. I can see how it will do nothing for front back rotational stress. How do jeeps with leaf sprung rea suspensions articulate differently than out trucks? The setups I have seen on there's are going thru 20" .

Then you have the 2 link versions that seem popular with the desert races that are single bar to a fixed single point to a lower bracket on the axle and a fixed hanger point on the frame both with jonny or hemi joints. They seem well proven in their use. But there placement and length is very specific for leaf spring travel and length etc..

I obvioulsy am not some pro fabricator and can only go off what I have read and seen operate on different vehicles. Cant debate the tech beyond that.
I have a set of Farmboy Fabrications traction bars on my truck....and eventually I will have a set of DPP bars......and I will do a complete comparison....

I will test them to the extreme, I do think there will be some binding(all bars bind to a point)......but I'm pretty confident there will only be a minor difference between the two.
Its a geometry thing and either you see it and understand it or its very hard to explain. I've tried before and people don't get it.

Basically, if you solidly attach arms to both sides of the differential, it, in effect, becomes a wide swing arm like on a motorcycle. The right side can't flex up or down independently of the left. No matter what joints are used.

These setups usually do flex though, either by bending the arms or by twisting the differential tubes or the truck frame. I learned about the latter when I was building my air suspension because one of the HD truck shops showed me a Dana 80 with a broken tube due to running a kit that did this sort of thing.

It might work OK on a Superduty though, I don't know.
dont stop there, this is usually the part where you explain......
I was speaking about it from the twisting of the articulation. I saw it that the jonny joints would allow more twist without bind. I can see how it will do nothing for front back rotational stress. How do jeeps with leaf sprung rea suspensions articulate differently than out trucks? The setups I have seen on there's are going thru 20" .

Then you have the 2 link versions that seem popular with the desert races that are single bar to a fixed single point to a lower bracket on the axle and a fixed hanger point on the frame both with jonny or hemi joints. They seem well proven in their use. But there placement and length is very specific for leaf spring travel and length etc..

I obvioulsy am not some pro fabricator and can only go off what I have read and seen operate on different vehicles. Cant debate the tech beyond that.
I have a set of Farmboy Fabrications traction bars on my truck....and eventually I will have a set of DPP bars......and I will do a complete comparison....

I will test them to the extreme, I do think there will be some binding(all bars bind to a point)......but I'm pretty confident there will only be a minor difference between the two.
Its a geometry thing and either you see it and understand it or its very hard to explain. I've tried before and people don't get it.

Basically, if you solidly attach arms to both sides of the differential, it, in effect, becomes a wide swing arm like on a motorcycle. The right side can't flex up or down independently of the left. No matter what joints are used.

These setups usually do flex though, either by bending the arms or by twisting the differential tubes or the truck frame. I learned about the latter when I was building my air suspension because one of the HD truck shops showed me a Dana 80 with a broken tube due to running a kit that did this sort of thing.

It might work OK on a Superduty though, I don't know.
so what your saying, is in effect, it will turn the axel into a big sway bar?
Exactly ! That is exactly what it does.
I think the main thing to remember is....most of you guys don't offroad or flex your trucks often....so you 22" chrome rim guys on 35's won't have to worry about anything...

....it's the few guys on here like me that might see a noticible difference in binding.....but I'm not positive....so I'm waiting until I do the test before I guess what the outcome will be......no need to bable any negatives until it has been real world tested.
I think its important that people understand how things work before they put them on their truck.

If the arms are solid on the diff and the diff articulates, something has to give. This is why people build 4 link suspensions rather than swing arm suspensions.

And no, swing arm suspensions are not used on desert trucks. Nor on Jeeps.
I think if you move the forward rod mounts toward the center of the truck you regain articulation. Of course this presents its own problems with missing the drive shaft and making up a central mount.
i totally agree, 99% of ppl who is on the street 99% of the time, will never have a issue. you, in the off roading, and me, in some field entrances and creek crossings, fall into the 1% and will tweak quite a bit. i dont wanna single pole design, but sometimes we gotta eat chit. but like you said, we are no where near that point yet. just wanna make sure before i dish out $600 that it will work for MY application. keep us posted tank, im really interested in your results.
I definitely get it acts as swing arm there is no way around it when you lock at two points on each side of the axle. I was only thinking of a way to get more articulation with less binding out of the basic design. Big dif between running a single triangled trac bar as done on the jeeps and other rock crawler next to the drive shaft versus running two as the full size PU etc are trying to do. If there was a cross member attachment point rather than frame rails you would have more flexibility in what you could do.

Even the desert trucks in 7s class with leafs are running the trac bars only to 2 links when they run one on each side. Much like OUO but with a jonny joint at the hanger instead of the post and bushing. Each one is also custom setup for that particualr leaf spring axle setup. They did seem to be shorter OAL though. Travel was 16-20" IIRC
i would have to agree with me2. a johnny joint wouldnt help with the articulation he is talking about. articulation might be the incorrect word.

if you think of your sway bar(s) on your ex, if you put a jonny joint where your rod/bushings are, it wouldnt stop the sway bar from doin its thing. its functionality would not change. by welding the trac bar to the axel, it turns the axel into the sway bar, (same shape, mounting configuration) therefore when you get, even body roll for instance, it will want to twist the axel. it will push one bar up, and push one bar down.

like i posted before, only extreme circumstances would this be a problem, but you havent seen my truck goin some places i have to put it either.

pulling our stump grinder into a field through the ditch cuz corn was still up to get to someones back yard, tweaked me bad enough that my rear sway bar bent, and stayed bent. you could lay it on the shop floor and one side was 1.5 inches off the floor. it was 3 weeks old, so i know it wasnt bent already. i couldnt square up to the ditch cuz the grinder would not have made it in, or the truck for that matter.
@tree trimmer- you either need to fab up some quick disconnects for the leading end of the traction bar or dont use them because they will totally negate any suspension articulation that you have. By design, of course. I had some on my truck that were simple pipe with heim joints. They were great pulling the skid loader and trailering but when you get to the timber or any other place that isnt flat you have traction issues. I took mine off and the result is broken leaves in the rear spring pack. Its a catch22...
Yes I can see this. Where I got a bit screwed up on it was going from a centered single trac bar to one on each side.

You having your sway bar tweaked brings up something I have been looking for. Why are there no QD sway bar links for the SD etc..

It woudl sure be nice to quickly disconnect the front and rear ( actually run a rear ) when you needed it. There are certainly a few ways to do it. I know Donahoe Racing was in the process of making some before he went under and ICON was born.
Glad to see you guys understanding the geometry issue now.

If you want to do this right, make 1 bar that goes near the center of the diff up to somewhere near the carrier bearing. I've seen that done on a number of race cars. You'll get torque control without affecting articulation.
I know you have your hands very full right now so if its too much no worries. What size DOM would you consider good for that?

Running one next to the drive shaft also can somewhat protect the drive shaft
there lies the rub, standard use on two single poles is 2" .250 wall. so what is twice that strong, if your gonna only use one. but where would you mount it on axle?
instead of using bolts, could a guy use hitch pins? a 5/8 hitch pin with cotter pin? i realize thats crude and would need refined. or would the fact that its not tight (nut and bolt) affect it?
With only one bar in the center you should be able to run two link pints on the axle at/near center and not have binding. A shackle single point at a cross member point.

I have some ideas as I like some of the ideas of the OUO mount but want to incorporate it with a shackle for more extreme travel. Going with a single traction bar centered takes care of the articulation binding issues. Done right I should have drive-line/pinion protection and something else to hit and possibly slide on other than the drive-line. On the front end if what I am thinking works I shoudl have plenty of travel in all directions.

No the only issue is if I could weld worth a ####. :hehe:

I will try to post up some drawings or pics to see what you guys think



I still want to see the pics of the current ladder bars to see how far they can go before binding. As we are all stuck on absolutes here most guys as said do not do any real OR and even those that do unless they have a kit they are not looking at any serious articulation travel. For pulling/racing and mall crawling street stuff whihc is 90% of the people these are gone work great.
That is exactly what I was thinking for a down and dirty way of doing it. The only hitch and for me it is not one is you will want to be on level ground for the connect /disconnect. How or any popping and clunking do you think there will be doing that? Whats nice is the Jeep guys have made just about ever forum of disconnect that can be contrived so there is plenty to copy. It just needs to be beefed up.



For the trac bar I will weld up brackets right at the edge of the dif not sure which side yet. For the front mount I will need to get under and look but possibly a hoop welded into the side of the frame and a mount at the apex or a full cross bar. Can't picture the underside right now and am too lazy to go out to the workshop to look. But I think I have come up with a sweet idea. It will take fabbing or more welding up a custom front combo joint but I think its gonna work. I need to go looking on some site like pirate as I know I can't be the first to think of this. They may have something more developed as its always nice to allow other find the issues. LOL
 
#3 ·
Some more traction bars:

CJC Suspensions





OUO Traction bars/traction block bar combo










Anyone with others please feel free to post them up so we can look at and as many as possible.
 
#4 ·
It should be noted that ALL taction bars at some point will cause binding. But what matters is do they casue binding at a point before the rear suspension has fully cycled or full articualtion. If a trac bar will bind at 20" of one sided articuation it doesn't matter much if the suspension is only capcable of 16".
 
#5 ·
I agree with a lot of what me2 has said in regards to geometry and articulation.

Triangulated bars only allow so much movement, hard to make them work well without a lot of binding


When it was time to get bars for my work truck, I looked at all the different designs out there. And I could have gotten some brands for free or severely discounted, but I chose to buy the OUO bars because IMO, they are the best option out there.
I tow and haul often with my truck, and it didn't like backing a 10,000lb trailer uphill or on uneven/rocky terrain as the pinion would try and take a big nosedive. I also would get some nice wrap while snow plowing. The OUO bars took care of all of these issues and haven't caused any binding even when crossing a steep ditch at an angle with 2500lbs in the bed.

Here are some pics:









 
#6 ·
now a single pole design wont have the problem of "turning the axel into a sway bar". the trade off i think would be it eventually would bind on suspension collapse. if a guy used a ladder bar, but only one, and mounted it just off center like tarm was thiking, used a shackle in front, a busing on the top mount to help absorb some "shock" and act as a slight cushion, and a heim joint as the bottom mount of the shackle. i think that employs all the bonuses of them two designs, and i think it would negate all the negatives. ideas? apparantly, as a single ladder bar design, it would be have to be pretty beefier than a standard "set" of ladder bars
 
#8 ·
i got a real stupid question. I got my DPP bars last week and found a welder to put them on, he wants to know if the suspension, the back of the truck needs to be in the air, or leveled ground. I'm not quiet 100 % sure so please help me out, i like to test those bars.
Thanks, Frank
 
#10 ·
You also want the shackle to be at a 90 degree from the top bar. That way the pressure put directly vertical on the shackle and mount. It also allows for the correct range of motion.
 
#11 ·
So is the OUO bars supposed to be the better design for off roading at this point? I will be needing bars for my F-150 soon and want a design that will let the rear suspension do it's job when I'm on trails with it. I'm kind of scared that I will hit the bars on rocks and such though... Was thinking about some caltracs also, but not sure how they will effect the suspension off road either.
 
#12 ·
This is true only if you are wanting to go with a dual traction bars and you want something that will not require extra fab work.

I have a post I have been working on from all the info I complied from to many hours on off roading and desert racing forums.

For most the OUO design will do fine and out of the various ones made specifically for the SD (not all that necessarily will work as there are many others not directed at the SD crowd) they are the best. I explain this in the post but I will say there is 2 issues with theses for those that do take there trucks for serious 4x4s:

One: Ground clearance. To make a single bar work very well it MUST be mounted below the axle. The farther below the better the performance. Its physics. Take a look and you can see how low they are. The bars themselves being two of them also create areas to get caught up. It a product of the design has nothing to do with quailty which is tops. Think about what is going to happen if you take your front end up over a tall step or think about a downed tree. Whatever something that is wider than the truck but that fits under it without hitting the frame. When it comes to those two single tube bars gusset or not. The ones I have seen because of the low axle mount point hang are down low. Again these things may not be an issue for many peopl or those that only hit beach sand dunes but rocky or wooded off road or washes/ creek beds you come down on those or drag up on them....

Two: The other that I think all acknowledge is they can not perfect match the leafs arc even with the bushing there is some although it may be minor binding. This is another reason for such a long length past the front of the leaf joint. The adj version allows you to try and get it to the best sweet spot and leafs do flex but at the same time these are leafs for heavy trucks they do not have the flex nature and give. But these do work.


The idea but it does take fab work. Yes a kit could be made but its certainly more involved. That is a sling ladder bar with a front mount shackle with jonny joints mounted as physically close to the center of the axle( pumpkin) as possible. Doing this with a single one allows for full travel of the leafs and the arc they travel in. Thru full travel or arc the change effect on the pinion is about a inch and this is on looong travel leaf springs.

Go on any off road site and look at any of the real offroad rigs that are running leafs and you will almost exclusively see nothing but this single ladder bar with design.

This setup is are the ones that will allow for the most bind free travel and also allow you to make changes to the anti-squat effects of the rear suspension and axle. It also has a number of other benefits as well for those that do actual off road.

If there is interest in all of this I will post up the info. Lets just say there is a crazy amount of info on pirate4x4 and other sites and I think I may have now read most all of it. Made my head hurt:shrug:.
 
#14 ·
All of these traction bar threads have been interesting for sure, and thanks for consolidating. For me, there were a couple of posts in other threads that pointed out some key details that I had missed and made things clear. One, for the single bar design (e.g. OUO), the length/spring arc issue is solved by the fact that the rear mounting point of the leaf spring is significantly higher than the front wrt to the vehicle frame. Therefore, as the spring compresses and lengthens, the axle is actually moving nearly straight up and down, i.e. not moving fore/aft very much. This allows a long bar with a small amount of give in the bushing to move without binding for most setups that don't use extreme arch and travel. The second "a-ha" for me was the torsion/twisting component on the axle with the triangulated bar designs when the suspension flexes unevenly. Not even heims and shackles will solve this problem, unless I'm still missing something. So, to all who have contributed to these threads, thank you for the insights... Might save me from an expensive mistake! :D
 
#16 · (Edited)
i kinda cobbled together a pic in photoshop. basically the same thing as dpp's bars, but where his weld to the frame, these would be seperate. everywhere there is a pink dot, would be a hitch pin, for lack of a better idea. would make dpp's bars a QD.

the question being, do you think that with it just being a pin and cotter pin, that it would eventually woller itself out? it would be made out of 1.5" sq tubing, everywhere a pin would go, would be a pipe welded through the tubing as a "through bushing", with a grease zerk.

the issue i have with a single ladder bar idea on a street truck, is to effectively mount it, the fuel tank is in the way. to get a brace across frame to frame.

just kinda throwing ideas out there.
 
#17 ·
I have thought about building my trac bars with the QD mounts using tractor top link pins and the lynch pins to keep them in. I don't think those would woller out. If you used a 5/8" pin and could make your sleeves with an 11/16" ID to 3/4" ID I think that would be enough gap for grease and wouldn't bind up the pins.
 
#18 ·
Brian,

while that is true it in now way changes the fact that the bar and the axle are moving in identical arc. The leafs is not a perfect track. You can get close but there will be points in the travel where there is tension. Also do not forget on the SD's the axle is not mounted at the center point of the leaf pack until 2008+. With those you are correct its almost up and down but it still is not its closer but not. On the 07 back the axle is offset to the front. Regardless, forget theorizing what the axle does IMO the only definitive way is to watch. You will notice it moves in an arc. Further now add in articulation for a compounded travel path and to all different varying degrees of both. Consider this is it was true and axles becasue of the shackle point did move perfectly in a vertical path then we woudl not even be messing with ladder bars and the like we would be slapping on sets of parallel bars as part of a 4 link setup. You could for both of these issues though fab up a floating axle leaf mount system so it could move to a certian amount independent of the leafs. Something to think about. The reason you can not is it doesn't. the But as I said leafs are flexible and the one part of the OUO setup that I really like but with different parts is the center post and rotation around it. AS has been said for those not doing serious off roading or extreme travel this will work. It obviously has so its not like it can be denied. Nothing like real world proof. But at the same time consdier that most are running about 10" of travel as the setups are based around a block and factory spring. take a really flexible spring that pulls 16"-20+" of travel and add to it all kinds of obstacles to get those bars bent or hung up on. Again this is not what most use their trucks for. Face it if dual bars were the ideal for this that is what you woudl see rock crawlers etc running and they do not. They all use single ladder bars as close to pinion as possible.


Tree trimmer,

Sorry I am a bit lost why are you doing this? with the pin etc? At first I was thinking you were speaking of the QD sway bar links.


About the front mount of for the single bar: Do not forget that the forces while strong are focused upward if properly setup. Just one possibility:


Not saying that will fit per say but it opens the mind to possibilities There are countless others that do not use a full cross member but some type braced mount. I do not have saddle tanks to worry about on the X as it a rear tank. If you are running be tires that will not fit underneath anyways might want to look into on of those tanks. They are 45 gals. If you combined that would be one hell of a touring range. :eek:
 
#25 ·
What the heck are those things going to do ? It looks like they pivot right in front of the axle, allowing it to twist. They might stop the axle from going front and back, but they won't stop it from twisting.
 
#21 ·
Here is the post I was working on dumping all the various info I found as I went. I know some of this will be a repeat of info I already posted but I do not want to have to go thru all of this again and I doubt it hurts anything.
My main goal thru all of this has been to learn given I was pretty much sold on the dual ladder bars before all of this. Obviously I needed to learn a lot more.

What I have found in doing some basic CAD stuff and working out geometrically as well as spending hours and hours over on pirate4x4 and dezert racing forums the last week researching nothing but traction bars:

(I may or may not get some of this wrong and I am not certainly in now way stating that what I post is in any way definitive. It is only what I have or think I have come to understand about the workings of the traction bars etc.. The best thing that can come from this is it generating questions possibly debate and best of all ideas possible completely new or old proven technical understanding. )

If you desire to run bars on each side of the axle and want reasonable amounts of articulation with travel then you MUST only run a 2 link system. This is how the OUO is made. The real issue is that when you do not use a shackle mount that allows for the leafs travel it will cause travel binding of the spring but it can get close and the bushing does take some of the bind. You can get very close but there will be some binding. Now the fact is the leafs are flexible themselves. Just look at what they do when you run thru some obstacles etc. So being strong enough the bars can force the area of bind into the leafs and make them flex to allow for it.

This is not ideal but it does work and does allow for in general the easiest install and symmetrical look to the system. That is why the OUO is so popular. They add welding gusset to help limit the weakness of single bar setups which is bar flex. The post frame mount with bushing allow for 360 degrees of limited travel. Also being so long it minimizes binding thru the travel range and articulation. The one issue with this system is to get maximum performance the axle mount point needs to be below the axle and the farther below the better the bars performance. This does create lower ground clearance and a place to get hung up or slam into objects. No way of getting around this other than to make it so things slide over in in the forward direction but its still a clearance reduction. But again this is something obviously many can live with as most are not seriously off roading these full size rigs but some are.

Now if you want absolutely no bind in even some of the very extreme travel and articulation of the leafs and rear axle and also want the utmost in control over wrap as well as being able to actually have some control over antisquat of the rear end you need to look at a 3 point A frame traction bar. Notice I said bar not bars. You need the traction bar run as close to the center line of the axle as physically possible. This means right up against or actual on the differential. It you can picture this the shackle front will allow for the frnt -rear movement the leaf spring cycles in and becasue its only a single bar very close to center it will allow for extreme articulation without binding. By using jonny joints or other similar joints that allow allow of lateral rotation at or near center will allow for all the flexibility you need.

This type of single A-traction bar is what dominates leaf sprung long travel/articulation off road rigs. It can be made plenty beefy as well. The issue with these for a company to offer is they require some creativity in finding or fabbing a front mount location. One of there other benefits though is they can be designed so not only do they offer complete suspension travel and articulation without binding but also can protect your drive line and pinion from damage with only the very minimal of ground clearance loss. Many times far less than a number of dual traction bar setups do.

In side this single arm A frame traction bar basic design there are a number of ways to achieve each of the points. Each have there pros and cons. I will farther down to list the various types I have found and try to list what I have learned about them. In no way take this as I have any kind of real world expeirnce with them. I can only go off what I have read been told and have seen with my own eyes as some of these rigs were put there their paces with these different setups in use. I can tell you this out of all the really serous off road rigs that are using leaf springs for what ever reason none of them use dual traction bars ( one for each side of the axle) They ALL use a single traction bar in some version of the A frame design. That shoudl be very telling for those looking for the utmost in performance when it comes to suspension travel and articulation.


Obviously for position the goal is as close to the center( pinion location) as possible for the 2 axle mount points. How you fab you mount points both on the axle as well as up front will dictate whether it goes next the differential on one of the axle tubes or actually on the differential itself.

For the front mount if there is no cross member to attach mount points to some thing will have to be added which can be a full or partial cross bar. It can be bolt or weld in.

How you setup but both the length of your A bar setup as well as the shackle or whatever front pivot point used will effect how the rear end reacts when torque is applied i.e. Anti squat. So it really does matter how you setup these things up based what you are looking for in performance. IMO unless its for mud bogging or some competitive sport where you really want to plan the tires hard (high positive anti squat) you want to get as close to a neutral balanced point as possible. As this is a leaf sprung system this will not be an exact science like it woudl be with a 4 link for example. With a leaf spring locating the axle, there is a lot of flexibility and the axle doesn't really move in one perfectly defined path. But leafs do work well its just there is a bit more slop to the calculations.


The assumption is that the leaf spring's contribution to locating the axle can be represented by a horizontal link at the axle center line. Given that to find the side view instant center, you draw a horizontal line through the axle center line. Then you draw a line through the pivot points of the shackle. It doesn't matter if the shackle is in tension or compression or whatever angle. Where those two lines intersect is the instant center.

Picture copied from "Gordon" on pirate4x4:


Squat/antisquat effects on vehicle



SO while it seems lowering the bars connection to shackle point will lower anti-squat the reason for this is becasue it moves your instant center forward. What really makes a difference is making your bar traction bar longer. While as you can see from the first pic making the shackle angle longer will also more the instant center forward keep in mind the farther you slope the shackle from vertical the more stress(horizontal force) you will put on your springs. If you were to have a flat shackle it would be just like having a one link. It is best to keep shackle angle at 90 degrees to bar so force is directly upward and there is less stress. Given that changing the bar length is the best way to effect anti-squat.

So what does all this mean? Heck if I know!! No but seriously it can get confusing as we are dealing with a number of different factors.

* We are dealing with primary concern that got everyone needing traction bars to begin with: stopping pinion rotation from axe wrap.

* Then you are needing to set it up to prevent any binding thru the suspension travel.

* Lastly how the directing of force effects how the rear axle reacts when torque is sent thru to the wheels. Anti-Squat We want a neutral setting IMO. This will prevent wrap but also any wheel hop.

So in general you will want your traction bar to be at least as long to mount where your leaf springs front mount is. Actually a bit longer is better and certainly much better than being shorter. Its best if using a shackle to try and keep it perpendicular to the top bar.


With a shackle design the use of jonny joints gives the needed twisting to allow for all the articulation of the axle. The shackle allows for natural arc of the axle travel to happen with out binding and flexing the leafs and stressing the joints.

There is another type of front mount setup that also works calling a "slip and twist". It works similar to the slip joint on the driveshaft but also allows it to spin free (no teeth) So instead of high degree jonny joints and a shackle The slip joint can length and compress for front to rear travel and rotate for the twisting from articulation. It can be a simple hemi joint or bushing setup for mounting then. The main drawbacks with this type is friction, clunky you will fee it when you get on the pedal. It takes making sure the shaft is always well greased. Out tubing needs to be able to take the stress as well.

I will try to post up as many varying setup of the single ladder traction bar. Everything from shackle, fixed, slip and twist, various hybrids, etc.

One thing for sure if a traction bar setup can somehow take the place of a sway bar its gonna have issues with binding it has to same as with a sway bar.
 
#28 ·
90 is ideal but its not a must. Get it as close as possible. If its got to be a bit off error on the side of opening up the angle, meaning the bottom of the shackle closer to the rear and top of the shackle more toward the front. You will still have enough front to rear travel and actually the slight opening of the angle will actually more the instant center forward. Same effect as a longer bar. You want to keep it minimal as from what I can see the farther it goes the more stress gets transferred to the leafs.


This is not the DPP bar specifically and its running as a centered single but this clearly shows the angle of the shackle you want. For the rest it should be enough along with all the other pictures on DPP thread. Obviously the shackle mount will be installed on the frame rail.

 
#29 ·
The hoop mount was not to say that is the way 100% to do it. More just an example of different ways to achieve and good center mount and to get around clearance issues..


Another thing that mihgt be useful and can allow for changes if clearnace permits:

For a shackle type front mount, the shackle works just as well whether its in compression or tension. In other words the shackle can be mounted so the shackle is up from the A frame of the ladder bar or it can be in the inverse with the shackle below. This is usually done for clearance. In general its better to have the top of the ladder move more toward horizontal but for great ground clearance, routing (mounting) clearance, or to say protect the driveline better it can be mounted either way. What matters is the angle of the shackle to the bar and where it puts the transferred forces. Whether its pulling or pushing on the shackle is not very significant.


Its will actually work even if the angles are off by a good bit. The one issue you do want to not allow is for the shackle to invert when its going thru its arc. A very short shackle at an angle that when the axle travels thru its path cause the shackle to get pulled all the way on return could allow for it to return trying to go up. Trying to travel over the mount. Obviously it can not but it now would be jammed into the mount. Its easy to prevent and not likely to happen.


For a dedicated off road rig the slide and twist front mount works very well.


Treetrimmer,

One thing I wanted to clarify. It would certianly be ideal to mount directly to the pumpkin. But its not needed even with lots of travel. Its best to get it as close to the pumpkin but mounting on the axle tube is fine. With the degrees of angle allowed by the joints you are not going to have any issues with even extreme articulation on these rigs. The only issues that have been had were on the much smaller (thinner, weaker) axles was bending a tube or spinning one. Considering this is not happening even with the dual which are mounted all the way out and putting that much more force on them its not something that is an issue. A D44 could be a different story.D:

I would say 90% of the Traction bars are mounted to the axle tube next to the pumpkin.
 
#32 ·
Yes but wait til you see how its mounted to the axle. It creates a ton of stress on the mounting point. I would not be surprised if a number break and it does not control the pinion very. Look at it like a ladder bar with the top bar being flexible. Or a 4 link leaf in one control arm and the traction bar is the other.



Think about it rotating up and trying to roll under the bar what the leaf will do and what is or is not there to stop it. I sure wish I could get this all into my cad program and run it thru so I could break it all down to see what happens exact when.

Anyway I looked at how the effects change from the lower bottom mount like the OUO versus this.

Imagine the stress placed on that bar and the mounts with the mount location that close to the spring. With out any block I think it would be worse. I have read one post of a Nissan of all thing twisting one up like a pretzel.
 
#33 ·
wonder why they wanted it to pull on the bar, instead of push on the bar? and the most leverage/sheering force for the bolts is right there next to the axel like that. is another reason when they mount under why they are a ways under. it eliminates stress on the bar/bolts and gives the bar leverage on the axel
 
#36 ·
What do you do with your truck?

Is it a pavement pounder only or do you get into areas where you off road some?

Tow heavy much of the time?


Do you plan to use your truck for actual off road uses? By this I am not talking about mudding but going where you will be crawling over rocks washes etc where you would have the trucks suspension needing fully articulate with one wheel stuffed up int eh wheel well and the other side fully drooped.

Would your use off pavement be mainly mudding?




Different types of bars work better for different types of setups.
 
#39 ·
i tow about 8000 from time to time...i do go offroad as i am in the oilfield...the roads iam on suck..dont rockcrawl and dont go through mudpits...
 
#38 ·
That is the ideal. For someone that is looking for suspension cycling performance. That is not exactly the best way to say it but best I can come up with right this second.



I do though believe there is not ONE "correct" traction setup for all situations.


I think what we should try and do is list where each one has great benefits and where they have short comings.


Make categories but there will certianly be plenty of over lap. It will more be for the individual to decide where is there true focus and what other possible changes do they plan that could allow for more diverse usage. An example of the last could be a rig set for maximum off roading yet then you could add a rear sway bar if you designed some QD links and to me this woudl allow the best of all worlds. You also have to consdier those that NEED or WANT it to come in a kit form that do not require any fab work. SO really care more about looks and will want bars that have that look of a 4 link evenness with a bar on each side and noticeable.

I think once you decide what category you fit in you still then need to figure out what is the proper setup of any of the various traction bars systems. How they are installed and built can greatly where that force is directed.


What I am thinking of is something like this:
(all trucks in any setup can tow reasonable loads no matter what the setup as long as its quailty.)

**Trucks that stays on pavement and main duty/focus of performance is TOWING:

**Truck that goes major offroad over and thru obstacles ground clearance and driveline protection is all priorities as it a center of gravity that allows for traversing grades without tipping over. Real offroading.

** Trucks that do some street but do Pulling and maybe Mudding

** Trucks that do some of all do not need anything to an extreme


Etc...

then you have to factor is the other stuff such as how much does looks matter. Work you can do yourself. Ect.
 
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