# Adding Air bags for new vbox spreader, single or dual?



## Flyboy77 (Jun 23, 2014)

In a youtube installation videos, the tech mentioned a warning about using the T and a single path system to fill both air bags at the same time. He warned that in a turn the lean may lower pressure in the outside air bag and push it to the air bag on the inside of turn with less weight. Has anyone experienced this and decided to go dual path to separately inflate left and right? How much air would move between the air bags?

I'll be using a 96 F350, and considering adding sides to the currently 2 yard spreader (Hinniker stainless 775 with electric auger) to allow up to 3 yards. Even at 2 yards it's quite top heavy with current stock springs and lean was part of the reason to add airbags.


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## JustJeff (Sep 9, 2009)

I use a single path. Haven't had any problems at all.


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## Randall Ave (Oct 29, 2014)

You will be fine.


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## SnoFarmer (Oct 15, 2004)

Always plumb air bags in separately.
avoid plumbing the air bags together with a 'T'. If you do that then the bags can become uneven from one side to the other. Picture this, you've got a heavy load and you go around a sharp curve to the right. The bag on the left of the truck will have extra force on it now because of the natural tendency of the truck and load to lean a little outward through the turn. Now that extra force is pushing down harder on the left bag and some of the air from that bag will be forced through the 'T' connection into the bag on the right side of the truck. The extra air in the right bag will produce extra lift now on the right side of the truck causing the truck to lean even harder to the left. That forces even more air into the right bag and on and on until you exit the turn. I don't have to tell you that as your truck leans/rolls harder and harder through the corner you have less control. It's a bad thing and totally defeats the purpose of having air bags in the first place. I would imagine it would say something about this in the instructions. Just run separate lines to each air bag and you'll be fine.


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## Randall Ave (Oct 29, 2014)

What's your estimated gross weight loaded after you put the higher sides on? And is there a plow hanging off the front?


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## Flyboy77 (Jun 23, 2014)

@randall: I haven't estimated. I will normally have an 8' conventional Western on the front(~750lbs). Last weekend for ice storm I went without the plow and didn't like the top&rear heavy ride at all & ordered air bags. The guy I bought the flatbed from guessed 1200 lbs for it. Stainless 2 yard spreader empty is 550lbs. I'm figuring 4000lbs for 2 yards and 6000lbs for 3 yards of salt. No idea what my truck weighs. In my current config, I don't even like having 2 yards of salt in it without the plow. If air bags improve ride and handling sufficiently, I'll maybe consider stepping it up to 2.5 yards and try. The place I buy salt from regularly does 3+ yards in their 2500's, but that seems kind of scary to me and my fellow citizens.

@Sno: That was my point of this post (thanks for explaining it better than my 1 sentence did), should I worry about the lean and air transfer between bags? I bought the single path analog air compressor kit (Air-Lift) which requires said T unless I get a dual path. The analog dual path comes with line check valves (prevents pressure transfer at single compressor), dual'ish gauge and dual low pressure monitors. If I would plumb separate just to schraeder valves for manual fill, this would be easy. But I've popped an airbag in minivan by having it under minimum pressure with manual fill and want the automatic fill to prevent a repeat of my "stupid tax". Also time was a concern if going loaded to unloaded and pressure changes needed, didn't want to stop at gas station for air when time is most critical/profitable.

So figured I wasn't the first person down this path on this board and asked for other's experiences. Since JustJeff and RandallAve have suggested it's likely not to be an issue in their experience, I'll go with the single path that I ordered. I guess if I experience uncomfortable lean (I don't take corners fast and baby it when full), I will get the other required parts to upgrade to dual path. Hopefully I'll save the couple hundred more $ and the load will stay balanced enough.

If anybody has experienced bad lean and air pressure transfer (conceptually I get it), please post your experiences.

Not sure how much would transfer in real world when bags are both full at 50lbs. Seems like the theoretical would be hard for one bag to have 100lbs and the other at 0lbs, I would think the rubber would pose more resistance. With 2 yards in the spreader I was 1.5" above the bump stops on rear suspension when sitting on level ground. So the rear leafs will still be doing a lot of the work, but the air will assist and prevent so much lean.


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## 1olddogtwo (Aug 6, 2007)

I've never done a tee,( I swore I never would say never, ever again)

Please report back cause I've thought about it.


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## Flyboy77 (Jun 23, 2014)

@1olddogtwo: Do you have to manually refill or lower your pressure throughout a storm as you load or unload your spreader? 
How ofter do you have to check/refill your airbags throughout the year? These were my reasons for adding the compressor.

I will post back with my experiences on this grand experiment. Surely I'm not the first. But a lot on here have posted they prefer to add leaf springs instead of air bags. Too bad I searched too late and had already ordered the air bags.


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## Flyboy77 (Jun 23, 2014)

Air Lift does now offer a 5000lb set of bags that includes a jounce bumper (bump stop/timbren) on the inside of air bags that can run with 0lbs of pressure without damage. But I didn't buy those either. :-(


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## Mr.Markus (Jan 7, 2010)

I use single path as well without issue. Technically it dual path, one compressor. It does the back airbags on one switch and front air shocks on another with one dual needle gauge to monitor the pressures in the front and back.


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## Randall Ave (Oct 29, 2014)

What size line you run can dictate how fast/slow the air moves. But pressure is pressure. Run 1/4 inch lines. You are not going to have a problem. Your not putting in leveling valves, you are just dialing in the desired pressure.


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## Aerospace Eng (Mar 3, 2015)

Flyboy77 said:


> Not sure how much would transfer in real world when bags are both full at 50lbs. Seems like the theoretical would be hard for one bag to have 100lbs and the other at 0lbs, I would think the rubber would pose more resistance. With 2 yards in the spreader I was 1.5" above the bump stops on rear suspension when sitting on level ground. So the rear leafs will still be doing a lot of the work, but the air will assist and prevent so much lean.


Pressure change is not how it would work. Both bags would stay at 50 psig, but one would collapse and one would expand. However, because the airbags are simply adding preload to the leaf springs this doesn't happen.

The bags would still both contain 50 psig, and have a constant force. If one expanded and one collapsed, they still have the same force, since they have the same pressure. What the bags do not have is any roll stiffness (no self-righting forces). However, the leaf springs still have roll stiffness, and so as a bag collapses, maintaining the same force, the total force on that side increases because the leaf spring has to move for the bag to collapse, and vice-versa. So with a single system, you will have the same roll stiffness as without airbags.

With a separated system, you will have additional roll stiffness as the bag pressure can be different side to side.

The resistance of the air movement between bags in a single system is basically a damping function. The smaller the air lines the more significant the damping.


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## JustJeff (Sep 9, 2009)

I have the Air-Lift system (5,000 lbs.) with on-board compressor and a three pre-set remote about the size of an overhead door transmitter. I have the remote set for 85lbs. (full with 2 yards of salt), 45lbs. (half full of salt), and 7lbs. (empty) I don't really change it very often though. I set it at 85lbs. and leave it most of the time. The compressor comes on about once every half-hour for a few seconds and then kicks off again.


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## 1olddogtwo (Aug 6, 2007)

Flyboy77 said:


> @1olddogtwo: Do you have to manually refill or lower your pressure throughout a storm as you load or unload your spreader?
> How ofter do you have to check/refill your airbags throughout the year? These were my reasons for adding the compressor.
> 
> I will post back with my experiences on this grand experiment. Surely I'm not the first. But a lot on here have posted they prefer to add leaf springs instead of air bags. Too bad I searched too late and had already ordered the air bags.


I've always carried two tanks toolbox....2000lbs. I used the hole for the rear plate bolts. I mount air taps there, they also held the plate/trim ring on with the jam nut. 30lbs loaded or empty. Checked presure randomly. I kept switching trucks out and got tired of mounting the compressor itself and the kit. I swear on my 2017 I will use the full kit along with my train horns..... I miss them haven't used in 4 years


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## Flyboy77 (Jun 23, 2014)

See it is rocket science! Thanks aerospaceEng. 

Train horns would be so cool. I can think of a few times those would have been awesome to have!


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## Mr.Markus (Jan 7, 2010)

Aerospace Eng said:


> The resistance of the air movement between bags in a single system is basically a damping function. The smaller the air lines the more significant the damping.


Stay in school kids...I learned something today.


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## Mr.Markus (Jan 7, 2010)

Flyboy77 said:


> See it is rocket science! Thanks aerospaceEng.
> 
> Train horns would be so cool. I can think of a few times those would have been awesome to have!


 A friend of mine has them on his truck, when I was a kid in our small Town the train tracks used to cross the street at the gas station. (It's a trail now) I was fueling up a few weeks ago and he honks as he's driving by and I caught myself turning around excited cause I hadn't seen the train come through Town since I was a kid...


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## 1olddogtwo (Aug 6, 2007)

Also, I have a Viair compressor.....

Mount under truck, didn't last the winter and they wouldn't warranty it.....Salt.

Even tho it can be mounted under the truck....Wtf. I paid and challenged on C/C. I won.

I have the 4 horn set up.....Plus a 100 watt police srien.


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## Mr.Markus (Jan 7, 2010)

1olddogtwo said:


> Also, I have a Viair compressor.....
> 
> Mount under truck, didn't last the winter and they wouldn't warranty it.....Salt.
> 
> ...


I mounted my compessor under the truck as well, but inside an ammo box, it's been there for 9 years now and still looks brand new.

I had a picture of it on here but can't find my media since the site update. It's empty and I literally had hundreds of pictures on here.


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## 1olddogtwo (Aug 6, 2007)

We've seen some of your videos on line.

https://en.m.wikipedia.org/wiki/Mr._Marcus


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## Mr.Markus (Jan 7, 2010)

Of my big black truck...?


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## 1olddogtwo (Aug 6, 2007)

Look like a little black 2 wheel drive S-10...... you must have just washed it


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## Mr.Markus (Jan 7, 2010)

Polish and wax...


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