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Discussion Starter #1
I need to soften the empty ride of my dually quite a bit. I was considering either:


1 - Install Airlift bags and remove the lower leaf.


2 - Install Primary Air or Ketterman complete rear air suspension.


I know the complete rear will cost me about $1K - $1.5K more. Is it worth it? I had the bags on my 2500HD and they helped a bunch without taking the leaf out of that but it was riding on the bags most of the time. Either way I will also put in the Auto Level system.
 

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Hey Zeke!


I have been researching this as well. I'm gonna' install the PRIMARY AIR SYSTEM (hopefully within a couple weeks)......It seems to be the best out there, including those you mentioned!


I'm empty most of the time and I am willing to shuck out the dough if it helps my ACHING back like I think it will! (NO, Im not old
)


I will post as soon as I get it installed.....GOOD LUCK and let us know what you decide on!
 

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In option 1, which leaf would you eliminate? The bottom one is the overload. That will eliminate stage 2 bucking, but not otherwise soften the ride, if I am thinking correctly.





Michael
 

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Discussion Starter #4
Michael;


I have pretty much given up on the option 1 as it would not soften teh ride much form what I can figure.
I am looking at Airlift Primary Air, Kelderman 4 link or Kelderman rear unit only. The rear only unit puts air bags between the leaf springs and the rear perch. It is supposed to give a "softer" empty ride than their full 4 link system. Link makes a great looking unit for Ford and all Medium trucks but no GM "light" units.



The Kelderman rear system is the least expensive ($895 plus autolevel if you want). I am concerned about the twisting of the box beams in the Primary Air when one wheel is higher than the other. I have heard good and not so good about both units so I am still stuck.


eds04max;


Did you get the Primary on yet? I would like a report ASAP on installation and ride qualities. You will be the first "customer" i have spoke with on either unit.



Thanks, Zeke
 

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heh zeke, my concern was with the hitch twisting of the cheaper air ride from kelderman, if the bags are attached to the one piece hitch, does the hitch arm flex with the pressure of one bag being up and one being down as the axle tilts. it saids like alot of pressure to be put on a 2" square tube because it has to twist if one tire pushes up and the other drops. i might be wrong, i'm no engineer. just use to much common sense sometimes. common sense does always apply though.


john


02 3500 cc lb 4x4 lt
 

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Michael, no adjust on-the-fly, it is auto. (keeps truck at same ride hieght regardless of load).....I was confussed too!!



Zeke, sorry dude! I'm wantin it just as bad as you are but my tax returns have been slower than expected(almost as slow as my typing
)......although, one did come in today!!! I'm shootin for end of this month!...P.M. me, let's talk tech.
 

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Looking at those 2 systems, primary air is going to be a better ride, but I'd sure like to have a spring backup.


I just dont see a 300% benefit over $200 airbags (done right). Dump the overloads and the big removeable leaf. Mount the airbags (with a height adjusting plate if necessary) so that at 10 psi, the truck sits 1" higher than at 0 psi. You then have 1" of pure air travel before the (compliance reduced) springs begin to assist. That 1" has very low restoration force, about a 100 pounds per inch, unlike the stock springs, 1000 lbs per inch of travel. This is rough, but the idea will nee a little trial and error on the bag mounting/pressure. But I really think it would be worth it, and put the rest of the money into a tuner.
 

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Here is a settup similar to what I will do. It will allow digital pressure readings, man-off-auto switch, and switch for manual solenoid inflation/deflation. You can have it all and no airlines in the cab if desired.


http://community.webshots.com/album/57739133AWOJCV
 

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Mike, Anything will help the F350's ride. These do not make an appreciable improvement with the GM (reported) and it ends up 1" lower.


I am doing some research on the range rovers success using air. Some of this engineering should benefit the GM. I would like to do something with a predictable result, that turns the HD ride into a cushion, without losing the payload. I know it's possible without giving up the "horse and buggy" springs.


Will post more of my conclusions as they develop.
 

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Hey guy's in case you havn't figured it out, we are "plowing new ground" when it comes to 100% air ride (rear) so I think masterp2 is right in saying it will take some trial and error!! As I understand it, there are only a handfull on 2500 HD's nationwide with Primary Air, but it is the same kit as 3500 HD and there are many of those on the road.


masterp2, I assumed you were speaking of Primary Air being adjust on-the-fly. (we know what ass..u..me spells!!
) Didn't mean to imply you were confused....it appears you are well versed on the mechanics of what we are trying to do. It seems you are planning on some "slight" mod's.



If any of you guy's have discovered a system, other than previously mentioned, I would surely want to hear about it!!!!


masterp2, I hope your right about keeping the stock leafs, but I dont think our trucks will ever really ride "GOOD" until we lose the steel springs!
 

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eds04max


Shouldn't be too much of a challenge to manually overide an automatic system.


Here is the thing. The airbags everyone is using as add-ons, are not designed to improve the ride, they are designed to handle weight, like fat old ucle pete sitting on a beach ball, they are more or less spherical air containers.


Here is a ride quality bag designed for the Expedition 4WD.





The "ride quality" air "spring" is designed to travel much further, on a convolution, before it's spring kicks in. It's spring rate is nearly constant over it's range of travel, compared to the ride-rite's or leafs.





The thick vert black line is the static ride displacement. Looking at a rate of change of 50 lbs per inch. No wonder I love my expedition. The ride-rite/ airlift curves would be somewhat steeper, I believe.


I don't mean to hijack this thread, I hope this information is useful for your project, I'll keep this line of thought going because I am on a roll for my own purposes/project. But I am new to the community and I have scouted many of the big truck forums, this is the most informative and intelligent, and the designer did a great job keeping the page clean


I do not think the kelderman uses this type of spring, I can't tell from the pictures. But what the Kelderman does is provide some isolation from the springs, causing the truck to ride down on the bags before applying greater force to the springs. But you are still bouncing on springs, so you are correct. But here's the thing. Isn't ride quality pretty much evaluated for the 95% of the driving we do? For most of us that is highway or dirt road conditions where spring displacement of +/- 1 to 2 inches prevails. Making the ride float for that 95% is the goal. The Kelderman probably does this very very well, though, even if using the beach ball type bags. Nonetheless, a bump must be transmitted through the spring to the trailing shackles and then to the airbag. Having the old stock springs suspend you if they go flat, makes this design my vote. And for the guy who was going to buy a hitch, it's a great value.


But I can't really tell if the Kelderman reduces "independence".. Are both sides connected, or does each side ride independent on it's own bag without applying force to the other bag? If it is independent, that makes for side-side load adjustment potential.


The range rover (4 wheel independent air) incorporates enhanced independence, the bags are interconnected with large diameter tubing. When the wheel hits an obstacle, the bag is compressed and the transferred displaced air increases spring rate on the opposite wheel (or diagonal wheel, I'm not sure). It is engineering to maximize traction on the drooping wheel, and increases articulation in off-road travel.


This is turning into more than 2 cents, but if helpful, that's the idea.





Michael
 

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Hey guy's, I saw a Kelderman setup on a C4500 Kodiak today......looks sharp! (it's a good thing too... very visable. It hangs low.) No time for a ride, but I will see him again soon and get that test ride! Owner say's he LOVES it! I'll post after ride.


BTW...still havn't installed mine. Seeing Kelderman has me second guessing myself!


masterp2, I was "told" that these systems (bags) ARE for improved ride.
...........I better not get too deep here, you know more than I want to know!!!
..seriously, this is good info.


I agree 100% with comments about this forum...AWESOME!!
 

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"I was "told" that these systems (bags) ARE for improved ride."


If you mean Kelderman, I agree, though I would like to see a dispacement curve (shown above) for the rubber they are using. The flatter the curve, the nicer the ride.


But the 5000 lb air rides are built for load, with a steep curve. i.e. has dramatic increase in force with displacement from rest. You know, springy, like bouncing on a beach ball. If you call up the manufacturer, they say that as well. I asked if I could improve the ride with them, they said , no, not by themselves. To mean that the leafs still operate the same way, in concert with the bags. I agree with them, that spring compliance must be addressed. Kelderman does this with leverage. The truck load interacts mostly with the bags before the "excess" is handled with stock leafspring deflection. Nice design that preserves the axle dynamic.


I have spoken to Adam at Arnott, who is interested in developing aftermarket comfort air bags using the one shown above as an alternative to the rougher air-ride. An aftermatket add-on that would greatly "float" the ride. As a minimum though, the overloads would have to be removed, for the nicest ride in a wide travel range. The overloads could be kept, if you don't mind a 1-2" lift and an occasional pogo on deep ruts. Even the Kelderman can't eliminate this if the overloads are retained.


I think the self-leveling recipe without the overloads would be the sweetest, and cheapest, if the bag above could be adapted to our trucks, yet to be demonstrated.


Just for kicks here, does anybody care about payload capabilty over 2000 lbs? (2500 lbs for 1-ton)?


I don't see the concern with any of these options.


Michael
 
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