I don't know if it was my post, but that is where I put mine. I read this because I know I posted on a post about airbags, but I hadn't posted here until now.
I read a post about connecting both air bags to one line. If I remember correctly AirLift recommends against this. Because if one leaks you would over fill the other bag. Also you can't be assured of getting the same pressure in both bags.

 

Ok, sorry for all the confusion. I guess i miss used the word pressure a couple of times in my first post. Sorry about that. Hopefully no one got to upset about it.

I'll try to clear things up in my post a little bit here.

Original Post
"I would not suggest using a T to connect the bags together. As one bag is compressed and one is relieved the pressure in the compressed bag rises and the pressure in the uncompressed bags drops, now there is a pressure difference and air will flow from the compressed bag to the uncompressed bag. Therefor the compressed bag loses pressure and weight capacity."

As far as this explanation go's everything but the last sentence is correct. It shouldnt have said it looses pressure, it should have said that it looses air volume, therefor is loses weight capacity.

One thing that i should have said is that this is happening vary quickly. Faster then the air can move through the air lines from one air bag to another. So for a vary short time the pressure in the bags will be different. Then it will equalize and the volume of the bags will be different, which will cause the lose of weight capacity.

Again i apologize for all the confusion i caused.
I know im no perfect, i do make mistakes.
I hope i helped to clear things up a little bit.

Good Luck

 

Well, I tried it out. I dropped the air pressure in the rear tires of my Explorer to 20psi. The tires had a pretty good bulge to them.

http://mistercmk.com/album/albums/us...2/DSC02510.JPG

Gauge showing 20 psi
http://mistercmk.com/album/albums/us...2/DSC02511.JPG

I then added 500lbs of roommates and water softener salt on the cargo carrier that goes into the trailer hitch.
http://mistercmk.com/album/albums/us...2/DSC02512.JPG

I checked the tire pressure and it was still 20psi.
http://mistercmk.com/album/albums/us...2/DSC02513.JPG

 

No Fordman, you are correct. The loss in pressure would be so fast you'd never notice though, since the air would flow as fast as it could to equalize the pressure.

500lbs isn't enough weight to make a difference, try the max the truck is rated for. I can tell you that my pressure guage will go up 10psi in my air suspension when 1500lbs is loaded into the truck. Every time... and bumps, which compress the bags as well, also cause the guage to spike. Tires have a lot more resiliency to them since they are so dang thick and strong. Airbags are much thinner and more complient, displaying changes in pressure much easier.

 

How much weight do you want? The tire pressure won't change. I can lift the truck up in the air and check again to make sure that they are at 20psi and then set the truck down with 500lbs in the back. It will not change.

 

Have you heard of the ideal gas law?

 

Your tire pressure will never change campared to load since you are not really "compresing" the tire. As you add weight to the vehicle the wheel is forced down, air in the lower part of the tire will be forced up to the upper part. It "deforms" the tire rather than compresing it therefore there is NO change in pressure. The only time your pressure will change is due to temp changes.

 

If you do it enough it will change, but it involves compressing the tire which is very difficult. However, airbags aren't designed the same way. They are designed to expand up and down. The hight of the bag may be 14" when its filled to 10psi, and might be 20" when filled to 100psi. That stack will compress under load. When a 50psi tube which is 16" tall is compressed by a heavy load down to 12", the pressure will increase. It does not bow outward to maintain the same internal volume. The volume decreases and the pressure increases. As the truck bounces down the road, the shocks expand and contract, varying the volume and therefore the pressure.

If you were to do the same test with two linked bags, and add a biased load, that side may compress down to 12" while the opposite side rises to 18". The pressure will be the same in both bags since they are linked together, but the volume in each will be different, and therefore the height will be different. This causes the roll that was described earlier.

Now if you had the same situation with two individual bags, you could manually lower the pressure in the high bag to level the load. Then you'd have two bags, one with 1500lbs of load, 60psi, and 14". The other bag would be 500lbs load, 30psi, 14". (all numbers are made up, I'm not actually doing the math, just illastrating the principle). This system would be rock solid and would not allow any unusual body roll.

However, most people, myself included, use a centered load in the form of a gooseneck/fifthwheel hitch. In this case you don't see a huge change in roll when the bags are linked together, but it is definately present. It is more stable to have individually controlled bags, even if they are always set to the same pressure. It is easier and cheaper to run them together if you have an auto-adjusting system like mine, although the definately offer higher end equipment that offers seperate control for each bag. It just costs more!

 

How much weight do you want? I am going to go out to the farm this weekend and my buddy and I are going to use his truck (which has airbags) and we will put a big pallet of seed in the bed of his pickup and I'll be sure to document the whole thing for you. The only reason to use his truck is that it is a heckuva lot easier to load weight into than my little Explorer.

 

If you are using true airbags not much is needed! It'll be pretty obvious very quickly. Depending on how heavy-duty your bags are. Load them to 2/3 capacity (with my F150, that'd be 1000lbs of the 1500lb capacity). Mine rise about 10psi, but they are the light duty ones. Heavy duty bags will have less pressure change.

Heck, just jumping up and down in the bed of my truck will make them change pressure. Not very much, but it definately makes the needle move! I have inline guages on my system.

 

Are we talking tires or airbags here? You seem to be jumping around quite a bit here. Sunday I will do both.

 

I have been and am refering to airbags, tires may be too difficult to display the principle I'm refering to. It is very noticable with airbags. I have inline guages with constant live-data so I can see every bump and change as load is added.

 

Thought so :P

 

Sorry, crappy weather kept me at home this weekend. Staying safe and alive was more important to me.