[BusNit]

Please also let us know if you do get the 1R11-066 bags. I think we are all curious as to whether they really are available despite websites showing "in stock"

[Ole]

I will but it’s proving to be a challenge which is why I was asking and trying to see if we could use the one I can get 20 of and just get them adjusted and maybe share with others.

[Richard]

Well, this is turning into an exercise on what to do.
I was a fan of the Firestone Bags, but obsolete is obsolete.

I did a great deal of digging in this Goodyear catalog  https://infinityairsprings.com/wp-conten...ate_v1.pdf

First thing, there is a phone number on the catalog for calling Infinityairsprings. That might be worth a shot instead of dealing with middlemen. 

Second thing I took the critical dimensions of the stud spacing, bag height extended and compressed, and tried to find alternatives that would not require much modification to work. I found some that would require new top holes closer together. All the alternatives had 1/4 npt openings.

Third thing, I moved on the look at 1 inch larger diameter bags. There appears to be plenty of room to fit them. There are two other reasons to consider larger air bags. One, is the air bag sizing from front to rear on the Ridewell rear/ DANA front coaches is out of balance. For example it takes about 80 psi to raise the front of my coach, and 110 to raise the rear. This is all due to the weight to diameter of the bag calculation. There have been instances where folks had air compressor governors fail, or air compressors start to weaken, and they could not develop 110 psi to raise the rear of the coach. The second reason is that all the alternatives I can find have a 1/4 or 3/8 npt air inlet. That means that the ping tank is going to be bypassed. I cannot quantify this but that will increase the spring rate when the ping tank is bypassed. Increasing the diameter of the bag will restore some of the spring rate. i.e. it will be softer.

So, to the best of my ability I was able to identify 12 inch diameter bags that will fit according to the dimensions in the catalog. The drive axle would take a 1R12-350 and the tag will take a 1R12-558. A couple of things to note. The drive bag will now have the air inlet as part of one of the studs. Also DO NOT put 12 inch diameter bags on the drive and leave the 11 inch diameter bags on the tag. This will put more weight on the drive and less on the tag then currently exists. The tag is already underweighted. If you don't keep the diameter of the bags the same I am afraid the tag tires will slide in a hard braking situation.

If I were a good boy I would have called Infinityairspring to see if those were more readily available, but we leave in the morning, and I am a bit busy. Also, the catalog lists cross reference manufacturers of those bags which may help in sourcing.

[Richard]

Ole, I have looked at the drawings of the air bag you listed. I think it may work with minimal work. As it is shown in the drawing, there are four bolts that attach the bottom to the bottom plate. However, there is one bolt in the center that holds the bag bottom plate to the piston. I would simply remove that bolt, replace with threaded rod and nut. Cut the threaded rod long enough to protrude through the existing mounting hole.

It appears from the drawings that these bags are larger in diameter. You are going to have to match that diameter on the tag bags.

[Ole]

Ole, I have looked at the drawings of the air bag you listed. I think it may work with minimal work. As it is shown in the drawing, there are four bolts that attach the bottom to the bottom plate. However, there is one bolt in the center that holds the bag bottom plate to the piston. I would simply remove that bolt, replace with threaded rod and nut. Cut the threaded rod long enough to protrude through the existing mounting hole.

It appears from the drawings that these bags are larger in diameter. You are going to have to match that diameter on the tag bags.

[Ole]

Wow, thank you so much Richard! I’m hoping the top plate also works as I believe it’s about 3/4 inch difference and the air intake is in one of the studs unlike the originals. The compressed and Extended height is off by an inch. I’ll let you all know what I find. Thanks again!

[Dystrakti0n]

So, to the best of my ability I was able to identify 12 inch diameter bags that will fit according to the dimensions in the catalog. The drive axle would take a 1R12-350 and the tag will take a 1R12-558. A couple of things to note. The drive bag will now have the air inlet as part of one of the studs. Also DO NOT put 12 inch diameter bags on the drive and leave the 11 inch diameter bags on the tag. This will put more weight on the drive and less on the tag then currently exists. The tag is already underweighted. If you don't keep the diameter of the bags the same I am afraid the tag tires will slide in a hard braking situation.

If I am following, this is relevant for the 1991 year model as well?

[Richard]

I do not know. You could measure the bolt to bolt dimension on the top plate and compare with the drawings to confirm.

[cwl1979]

This seams to be the topic of much discussion and many doubts on availability. I'm not going to pay over 250 for an airbag. The key things to look for when changing them to a newer style is the bellows, bolt spacing, and compressed height. The base is irrelevant, unless your base/pedestal is broken. the main section of the bellows can be removed from almost every bag and replaced with the base you have on your coach.  With that being said here are the closest and least fabrication needed bags to use as replacements for the Firestone 9447 bags.
First we'll start with the dimensions of the "stock" 9447 bags that are impossible to find.
   
You'll notice the key features are the impossible 1 inch inlet and the center plug is a 3404. collapsed height is 4.80 inches total ride height is 13.80 inches not counting any over lift that might be used.
Next we compare this to 9477
   
This bag will work for you with only needing a 1inch to 3/4 reducer on the air inlet. lets say you cant find this bag (or in my case they wont ship to Alaska) we can look at other bags that will work.
   
This bag will also work. Same thing needs a 1 inch to 3/4 reduction bushing. This bag is also readily available here. https://www.truckandtrailer.parts/contit...-001804591  You will need to remove the center bolt and reuse your existing pedestal. It is 1/4 inch taller when collapsed so you'll need to droop the suspension to get it in there

   
This bag will also work the downside is you will have to jack up the coach and "droop" the suspension because the collapsed height is 3/4 inches taller than stock. You will also need the 1 inch to 3/4 reduction bushing and reuse your existing pedestal. This bag is also readily available at the same place.

If for some reason you cant reuse the existing pedestal grab a Dremel tool with a tiny cutoff wheel and remove the 2 studs from the bottom of the new base. Remove the center bolt holding the pedestal onto the bellows. Then before installing into your coach get some new standard center studs and reinstall using the center stud to hold everything together. 
Ill be replacing all 8 with 9376 as i can get these locally from Trailercraft or Peterbilt for 165 each. However this will be done in the spring as there's no point doing it now just to let it sit outside and freeze. I've also added the firestone catalog and the goodyear to the bottom as PDF files As well as a link to the best cross reference site i have found.

https://www.truckandtrailer.parts/air-sp...ences.html

[Richard]

Thanks Carl. Great work !