Which is better, air bags or springs?

[SHobbs]

Anyone using the 4 link systems like Kelderman offers. Worth the cost as far as ride quality and load capacity or not. I have looked at them and being the tinkerer I am I am considering putting together my own system.

 

[SRadke]

I have one and there are pictures in my gallery. Worth the cost... . depends on you.



Axle wrap found in the stock leafs, compleetly gone.

Ability to set level or have auto level.

Adjustability in height of about 6"

On board air



The ride... similar to stock empty. Where it really shines is under load because it never bottoms out.



-Scott

 

[randyn]

Re: sway control



I put air bags on to help w/ my 2500 '03 and it helped the swaying a lot. I have an outfitter popup camper, and was initially very concerned w/ the swaying. The bags leveled the truck and cut the swaying by more than half in my opinion.



RandyN

 

[DPelletier]

In my experience (and the opinion of the local spring shop), air bags aren't the answer if sway control is the primary goal. They may have helped you some, but they made mine worse. Of course my camper would weigh double what yours does. Don't get me wrong, I think air bags have thier place, I just don't believe that sway control of a large slide in is it. When and if I get a 5th wheel, I may go with the air bags.





Dave

 

[GFritsch]

Since this tread has taken a slightly different twist and has been around a while...



Does anyone know if Rancho makes a dual shock set-up for 3rd generation trucks. Seems like air bags and extra rear shocks might be a nice set up.

 

[y-knot]

Of-coarse you can use a portable air compressor to fill the bags. Only thing is you will miss out on the best reason to own air bags, they are infinitely adjustable. While going down the road, you can adjust the pressures to suit the environment. Roads a mess, and filled with potholes, just add or subtract a little air, depending on what you were running at the time. This is the reason I have run airbags for over thirty years. They are great, and allow the vehicle to adapt to the present environment. Running without an on-board pressurized air system would be like as satisfying as a Dodge without a Cummins. Sure you could still get there, just wouldn't be any fun. I got hooked on air adjustable ride control systems way back in college. I did several experiments with air systems and even applied for several patents of various ride enhancements. What I have found, is that by increasing the the capacity of the system, the bags and supportive lines, you can very much increase the ride quality. With a stock air bag system, two bags and 15' of 5/32" line, every time the suspension travels to accommodate a bump in the rode, the system pressure spikes. If you run say 50psi as a normal pressure, when the suspension Encounters a obstacle it travels over that obstacle, which results in the rear end housing traveling up and down. For simplicity, say the rear end traveled 3" which made the air bags decrease in their normal length by three inches. The pressure inside the two air bags and the small amount of line, is dramatical increased in a very short amount of time. That 50 psi of normal pressure, shoots to say 75-85 psi in an instant, then settles back down to 50psi. This spiking causes much more of the encounter, the bump, to be transmitted to the cabin of the truck. To smooth things out, and to achieve a truly velvet like ride, some sort of a buffer needs to be installed in the system. In stock, out of the box condition, there is nothing but line and bags. I like to install a separate air tank into the system, this tank is connected in-line with the bags and will always be at the same pressure as the bags. Now when that same bump is hit, and the suspension travels it's 3 inches, the pressure spike is much,much lower. The actual spike will be determined by the size of the air tank, but it does not take much to make a very noticeable improvement. Even a small tank, one about 1/4 gallon will lower the spike pressure enough to make the difference. Now the spike pressure rises from 50psi to only 55. There are way to many variables to be precise in this example, but you can see that by adding the extra volume to the system, it become much better at manging the system pressure while experiencing suspension travel.

This isn't rocket science by no means, just simple pressure vs volume differentials. I have a air compressor (QuickAir II) that pressurizes a storage tank. This function is automatically controlled by the use of some simple pressure switches, air compressor goes on at 80psi, and shuts off at 125psi. Mounted to one of the threaded boss's on the tank is a 12V solenoid, this is controlled by a switch in the cab that when energized it opens a valve on the main storage tank and fills the air bag pressurized system. In this system there are two bags, lines and a small tank. Both the main tank and system tank pressures are monitored in the cab, the ride can be varied to conditions with a simple push of a button. The result is a very nice ride, It seems the perfect pressure is the amount of air it takes to remove most of the trucks weight from the springs. This will change with load, but you will over some time, figure out what works best for you and your truck. That ability to change air pressure while on the go is the true beauty of air bags.

 

[Kyle]

y-knot,

Great advice. The addition of more volume to the system is interesting. What I hear you saying is that additional volume ("buffer" tank) allows the axle to travel more without reducing the load capacity.



The system I was envisioning would have the bags independent (not connected) to minimize sway. If I added a small tank for EACH bag, there would be over double the volume on each side (compared to just the bag & line).



There has to be a "cost" to this. I suspect the added volume -- even if the bags are not tied together -- would allow for more sway. Does that make sense? Maybe there's no real advantage to keeping the bags separated if you add the extra volume. What do you think?



Thanks to all for the advice. You've talked me into new springs, air bags, "buffer" tanks, on-board air, AND a sway bar. I thank you, my wife thanks you, and my banker thanks you..... Hey! my birthday is coming up soon... ... .

 

[LandShark]

Kyle: I've 'been there, done that'. We have similar trucks and campers. The biggest problem I've been fighting over the years is SWAY. Here's what I've tried and learned.



1) Overload springs: No help with sway and very hard ride empty.

2)Timbren: Good to fair sway control, but hard ride loaded.

3)Air Lifts: excellent level control, no help with sway, slightly harder ride empty.

4) Rancho 9000's: some sway control if on #5 setting but very hard ride on that setting.

5) Sway bar: Slight help with sway, slight loss of agility offroad.

6) Tires: You seem to have that problem under control. Tire flex with most 'E' rated tires when fully loaded is significant. I'm using Michelin XPS RIBS which are fairly stiff.



So far what I've learned is that the only way to keep SWAY under control is to drive slower or suffer a very hard ride when loaded.



How about looking into T. Rex type rear shocks? From what I've read and learned, that may be the best solution to sway control. I've not looked into T'Rex so far, because of cost.

 

[SRadke]

Buffer tanks are the way to go especially on large diameter bags. Keep the two sides independant and connect the bag and the tank with the largest line feasably possible. My system uses 1/2". This will help tremendounsly with ride quality but works adversly for sway.



-Scott

 

[y-knot]

I have tried to separate the bags before, it was just to satisfy my own curiosity, an experiment. I saw no notable changes, and with a normal load, there was no need to have one side stiffer then the other. The back of the truck seemed to get very jittery when a bump was encountered and the two bags were at different pressures.

The Buffer tank has nothing to do with load capacity, the bags will hold their rated loads regardless of weather you use a buffer tank or not. What they do is allow for a much smoother ride. The extra volume that the tank supplies, reduces the air pressure spike when a obstacle or bump is encountered. This makes for a more consistent overall pressure that also makes for a better ride. The buffer tank does not have to be very large, I built mine out of some stainless steel tubing I had laying around, it's only about a quart big. You could build yours that way, or go to the local hardware store and get a piece of pipe and cap each end. Believe it or not, PVC pipe works very well as a low pressure tank, under 125psi. It is very easy to cut and weights almost nothing. A foot long piece of 3" or 4" PVC and the required caps and adapters, and you are done. Just make sure the cuts are square, and use PVC cleaner before the use the cement.

 

[Rman]

Y-knot i'm looking into setting up onboard air controls for my airbags (I've just got the bags without any control, external fill) Is 220 a good price for a quickair III pump? I'm just going to plumb in gauges and a tank on my own, screw the kit thing.

 

[Kyle]

Rman,

I've been exploring on-board air too. Be careful of the Quick Air 3. It's a great unit and has one of the best cfm ratings for a 12-volt, BUT -- it's max output is only 70psi. From what I understand, that means you'll only get 60-65 to the bags because there has to be a little buffer for the pressure switch -- otherwise the compressor would never go off.



Just make sure you don't need more than that in your air bags.



By the way that price looks pretty good from what I've found.

 

[Rman]

wow thanks for the heads up, I do air mine up to 85-90 psi. I have a big heavy camper that needs support!

 

[SRadke]

I'm running a small Thomas compressor (327 I think????) that easily makes 150psi and would do the job you're looking for quite well. It's on the small end for my program but I've got 4 bags twice the size of yours.



-Scott

 

[SHobbs]

SRadke you said you have the Kelderman system, and stated that the ride empty was similar to stock. I thought having the bags without the springs would soften the ride considerably, guess I was wrong. I was under the impression that the ride would be softer, without all the jolts and bumps the springs have.

 

[SRadke]

Originally posted by SHobbs

SRadke you said you have the Kelderman system, and stated that the ride empty was similar to stock. I thought having the bags without the springs would soften the ride considerably, guess I was wrong. I was under the impression that the ride would be softer, without all the jolts and bumps the springs have.

The key word in my statement was "similar". The ride is diffrent than the stock ride but I hesitate to say it is much smoother. I now feel the little stuff in the road more than I did before but the big bumps are smoothed out. This may be due to the control arm changes as much as the airbags, I don't know. It also rides A LOT better with a load. The bags in the back are so big it only requires about 20 psi to carry the back of the empty truck. The surge tanks that y-knot speaks of can be sized to give you a very firm or floaty ride, it just depends what you want but there are trade offs.



-Scott

 

[SHobbs]

The key word in my statement was "similar". The ride is diffrent than the stock ride but I hesitate to say it is much smoother. I now feel the little stuff in the road more than I did before but the big bumps are smoothed out. This may be due to the control arm changes as much as the airbags, I don't know. It also rides A LOT better with a load. The bags in the back are so big it only requires about 20 psi to carry the back of the empty truck. The surge tanks that y-knot speaks of can be sized to give you a very firm or floaty ride, it just depends what you want but there are trade offs.



-Scott

I appreciate the info, I have been considering installing Keldermans system for a while, just trying to dot all my I's and cross my T's. You would think I'd be used to the ride by now, I have never owned anything less than a 1 ton.