Do I need Air Bags?

[mwilson]

Even without a big camper I would run the bags independent. When it's a single fill port you have one bag, so air moves side to side as the truck sways or leans into a corner. Even empty the truck has some roll on a corner. So when you are loaded (even if it's a equal and low load) and you go around a long corner the air moves from the outside bag, now there is more air in the inside bag and less on the outside. When you stop turning the air takes a little time to move back, so the truck isn't level and what if there is another corner the other way?



You also remove the secondary feature of the bags which is sway control, and as I mentioned can actually make sway worse.



The only people I have talked to that are unhappy with their airbags performance are the ones with the bags plumbed as one and they live in curvy mountainous areas.

Can you open and view this link???



https://secure.freightliner.com/ezw...GM&DiagramPartNo=D12-15908-000&diagramCount=1



If it opens does the control bar at the top work??



If so I will throw my . 02 in... .



Mike.

 

[MelvinPierce]

If you get the right kit the Bags/pump and gauge come as one no need to add other products to the game.



Sorry for the bad picture but hanging upside down looking under the drivers seat on one leg is a pretty tough thing to do IN THE SNOW AND RAIN

Compressor is under the rear seat compartment drivers side

This setup is what I have on my Ram. Works very well! I have the bags tied together. I see no need to have seperate air pressures. The load on a fifth wheel is in the middle of the box. If you have a truck camper or some such where you could load uneven, then maybe seperate might be good.

 

[mwilson]

Can you open and view this link???



https://secure.freightliner.com/ezw...GM&DiagramPartNo=D12-15908-000&diagramCount=1



If it opens does the control bar at the top work??



If so I will throw my . 02 in... .



Mike.

Just tested it on my i-pad, no go.



So here is a graphic, 46,000 Freightliner Air-Liner suspension. All bags are tied together.



If the tipping was a real issue there would be trucks laying upside down on every corner. I don't disagree that individual bag control would have it's advantages with a slide in but it is not mandatory.

Mike.

 

[AH64ID]

The big difference I see between the Freightliner and our trucks is that we use the airbags as a supplement, and not the main load carrying spring. In addition what size is the air line on the FL?

Like I said all the negative feedback I have received on airbags (personal, not internet based) has been from common plumbing. There is no way around the flow.

On a 3rd gen without an OEM rear anti-sway bar it would be even worse, IMHO.

 

[mwilson]

The big difference I see between the Freightliner and our trucks is that we use the airbags as a supplement, and not the main load carrying spring. In addition what size is the air line on the FL?

Like I said all the negative feedback I have received on airbags (personal, not internet based) has been from common plumbing. There is no way around the flow.

On a 3rd gen without an OEM rear anti-sway bar it would be even worse, IMHO.

Plumbing is 1/4" plastic air line. Kenworth's latest generation air ride uses steel tubing with at least 5/8" ID.

I'm not an engineer and have a hard time trying to explain what I know from firsthand experience.

There has to be a point where the bag can't compress any more under the load with a set air pressure and stops moving even with another bag on the opposite side tied to it.
The Freightliner system still adheres to the same principle and it is a hybrid, there is a spring with each bag.

When you go into a corner with a loaded air ride truck the cheeks of your butt try to tell you that it is tipping, then when that point of maxium compression is reached it begins to feel like you are sliding. If you are used to spring ride equipment it takes a while to get used to air ride.
I just wonder if the folks with the campers on the back with a shared system do not realize what is happening and are experiencing the same butt pucker feeling.

Not trying to argue but I can't reason why the tied assist system on a pick-up is any different than a four bag air ride truck suspension. The big rig does have a leveling valve that will add air but that air goes to all four bags while in that corner, not just the low two.

Again, I would do the individual air bag control with a slide in. I can see it's advantages. I just don't think it is a crash and burn if one chooses not to go that route.

Just my take on it.....

Mike.

 

[AH64ID]

There has to be a point where the bag can't compress any more under the load with a set air pressure and stops moving even with another bag on the opposite side tied to it.

That's true given a fixed volume, when the air can leave the bag then the volume decreases for a given pressure and you can still lower the bag, until you hit a physical stop.

When you corner with them the same the pressure tries to stay equal, so air leaves the bag on the outside of the corner and enters the air on the inside of the corner.

When they are plumed separate and you go around a corner the outside bag compresses and pressure increases, and you get more resistance and load carrying capacity pushing against that side, the inside bag increases in volume as the truck rolls and pressure drops giving you less load carrying capacity allowing that side to stay lower with the weight.

I just don't think it is a crash and burn if one chooses not to go that route.

Agree completely, there are just too many benefits to plumbing them independent, regardless of how tall the load is.

The only time I could see them being beneficial to be plumbed together would be in an offroad circumstance where you do not want to limit axle articulation. But with the small 1/8" lines you wouldn't get enough flow and 1/4" minimum would be very beneficial. I considered going to 1/4" lines on my old toyota with bags for this, but I was going to keep separate valves with a "T" I could open/close when I wanted. For street use it would always be closed.

 

[mwilson]

Just for grins here are a few pictures of the KW/Pete 8 bag air ride.



Check out the size of those lines on top of the bags, that suspension must react instantly to anything.



Or the lines act as a "ping tank" of sorts, there would be quite a reserve between 8 of those lines

... ...







Mike.

 

[BIGNASTY]

When KW came out with the 8 bag (looked different than the pictures) it was a seat pucker BIG TIME. Went for a ride with a guy that had it I was getting ready to open the door and jump cause I knew that it was going to roll. Pete's Air Leaf is what I had and loved that suspension. I have a single axle Air Leaf on the international rides nice even on a MDT

 

[ABennin]

Thank you guys for the insight. The independent setup has more benefits than drawbacks and I will pass it along. Thanks Andy

 

[Sarge]

Great info and good discussion guys, as usual. I didn't think of CL, I will check there for bags.