Air bags: what happened?

[Air345Fly]

I replaced my airbags with new ones. I was careful to use the all the
original bolts and spacers. Everything was torqued down properly.
Then I replaced both leveler valves. I pressurized the system to
check for leaks. The airbags pumped up then snapped to an angle
as shown. It appears that the lower airbag mounting bolt bent. The
bags are at an angle to the heavy bar that connects to both leaf
springs. The bar is at an angle as well. The motorhome is jacked
up and on blocks just enough to lift the tag wheels.





A lighter shot showing one bag:



The new leveler valve.



What happened and how can I fix this?

[Air345Fly]

I managed to pop the airbags back to the proper shape and get
the bolt out. I also got the airbag skirt out.


The bolt, actually threaded rod, is slightly bent.


I did not like the way that the lower part of the airbag was mounted.
The weight of the motorhome was carried on the spacer and nuts
on the threaded rod.

These diagrams show the airbag mounted with a threaded rod but no
spacers. I will reassemble it this way. It has the large center casting
of the skirt pressed against the heavy beam which seams much
better. This way the weight is carried by the large center casting.
You can see the center casting in the above picture but it is a
little dark.

8700-542-Model.pdf
8700-351-Model.pdf


On the other hand, the motorhome ran 33 years with the nuts and
the spacer.

[cmadmaxman]

Although I don't have the tag axle, the system is about the same. Mine has always had full thread B7 rods, no spacers. When I had the whole unit out, I added angles to capture the full footprint on the air bag piston. The piston must be tight to the support bar!

[cmadmaxman]

Also make sure that they are not over inflated. The height from the frame to the air bag beam should be about 10 1/2" +- 1/4. Going off memory on that dimension, but should be close.

[Smartstream]

The base of the bag should be flat and secure to the crossmember. The bag may bulge to the front or rear if the lower crossmember is not directly under the upper crossmember mount. The lower crossmember moves a bit as the spring flexes moving the rear crossmember mount. On both of my mohos I built an adjustable link from the lower crossmember to the differential tube. Keeps the bags nice and straight. There is a pic on page 5 or 6 of my "big sis little sis" thread but we are camping in Oregon and the Wi-Fi is so slow I can't post any pics. We will be home first of the week if you have questions.

[Air345Fly]

I reassembled both airbags without the spacers. This caused the
piston to be tight against the suspension bar. The piston skirt is
not supported all the way around, it would be better if it were.
But that is the was the suspension system was supplied by
American Carrier Equipment.

Might Airstream have needed a little extra height in the suspension
system and added the spacer as an easy way of doing that?

I pumped it up to full pressure and everything held.

Here is a picture from a different RV, not mine:


It clearly shows the skirt against the bar and without full support
for the skirt.

Here is the drawings for the airbag. They do not mention supporting
the skirt:
Firestone_air_bag_W013585412.pdf

[cmadmaxman]

Yes that is the way mine was (also my unit) and had no problem with almost 100k on the coach. While I had my complete rear end out, I went ahead and added the extra support for the bag pistons. At some point American Air Carrier added this support to the units. Don't know when, but think its a good idea!

[cmadmaxman]

Here is some more details on the system.

[stream3]

Originally Posted by cmadmaxman

Although I don't have the tag axle, the system is about the same. Mine has always had full thread B7 rods, no spacers. When I had the whole unit out, I added angles to capture the full footprint on the air bag piston. The piston must be tight to the support bar!Attachment 350294

That is one clean underside. Looks like a brand new coach. Nice!

[cmadmaxman]

Thanks, if I have everything apart, might as well make it look good