Important Note:   The original 2 sided Firestone air bag has been


Check out the new

 4 Air Bag System (Quadrabag) rear suspension

retrofit kit, with this system you will never have to worry about not having a way to replace your air bags.


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Yes, time marches on and the only thing in this world that is guaranteed is change.  Firestone has been supporting the GMC community for many years past the production end of our GMC with our unique air bags.  This double sides air bag was used exclusively on our one motorhome and for them to keep supplying a seriously low production part for these many years was fantastic and I say to Firestone "thanks for all you have done".  Time does march on though and now we are looking at a new age for our classic coaches, we need to modify our rear suspensions to accept currently available off shelf air bags to keep on the road and stay a viable option for travel.  Our new Q bag system not only does that very well but also offers many other very valuable features.

One of the most valuable features the Q bag system has for you is "resale value".  When someday your life turn you in a direction where your beloved GMC needs to find a new home, having been retrofitted to accept new air bags will be a serious selling point for any prospective buyer.  If they look at a coach with a pair of original bags, they need to think that the coach will need to be refitted right away.  Any coach already using new air bags will be top on their purchase list.  Besides that fact, the Q bag system offers you more safety and performance that the original double sided air bag system.  Read on and I will explain more about this.

If you've been here on our site for any length of time, you know we are promoters of the 4 air bag rear suspension modification for the GMC.  We have been installing these upgrade enhancements for over 10 years and in that time have naturally found features we would like to modify and add to increase the systems effectiveness.

To that end, we have been working with other respected folks in the GMC community and together have designed the all new 4 air bag system nickname the "quadrabag" , "Quad bagger" or just the "Q bag".  During the design of this all new kit, we looked at installation, reliability, strength as well as it's performance parameters to offer a superior product.  More weight handling capability, more up to down movement, lower bag pressures ( 80 pounds at full raise), easier installation (2 piece design) and built with heavier, thicker materials (3/8 steel instead of 1/4")-- yes, I am proud of this product and am convinced it is the best thing you can do for your rear suspension.  With this kit, your coach will have a full 6 wheel independent  suspension!

This is NOT a copy of the previous 4 air bag system, it is a new departure on the idea, safer, stronger and performs better.  Do not consider purchasing important parts such as this on a lowest price basis.  There are many considerations you must use to determine the value of a component such as this.  The previous system came packaged in a single box complete with all components and weighed in at 74 pounds, our new system must be shipped in 2 boxes for UPS to ship them each weighing in at 57 pounds each.  Just by weight, this new system is more value but do not buy something important like this by the pound OR by price, buy it for safety, buy it for maintenance ease and buy it for performance.  BTW, to know you have the best system look to see what the operating pressure is, if the pressure is over the rated bag pressure of 100 pounds, it is not our system--- throw it back!  It is not wise to operate any product past it's original design perameters!

Let me add something here, it's funny how much verbiage is being wasted to compare an older design with this newer one.  Time and progress marches on and there is little we can do to stop either one.  We here at the Co-op, have probably installed and dealt with more 4 air bag systems than anyone in this business and in that time have found challenges to make the systems better.  The "Quadrabag" system is a corroboration of many professionals, was computer designed and stress tested and has a perfect track record.  There is nothing we need to do to prove this system is superior.  If you do want to compare heads up though, come on by the shop here-- I can show you the difference.  I cannot feel bad about improving any product especially when we tried to work through difficulties but find the entire system needed revamping.  We are not copying any other system on the market, we have designed a reliable product strong enough to be abused and still do it's job and I feel thats the only way to do it.  You will appreciate the quality of the kit as you install it then appreciate what it does for you when you drive your coach.  Enough said, if you know me you know I do not pull punches, I would recommend the new quadrabag suspension system to anyone and would be happy to discuss this first person with anyone, give ma a call.


If you have ever wanted to do something to wake up the suspension characteristics of your 26 foot Hot Rod, this is it.  Bolt in installation (we usually say 5-7 hours time to install) with no cutting, welding or any of those things.  This may sound like one of those weight trainer infomercials but this is all true.  Take a look at the all new "Quadrabag"  4 air bag system and read through its features, if you have more questions or would like to order a kit for your coach, give us a call on our toll free line 1-877-275-4462.


o 2 piece construction for easy installation
o Outboard air line connections to air bags for easier connections
o Heavier gauge steel construction (3/8")
o Double 3/8" steel plates back to back between the air bags, no flex here!
o Larger, more weight carrying air bags
o Lower air pressure requirements (keeps operating pressures well under manufacturer recommendations.
o More travel up and down for height adjustment mainly because of the design.

Cost:  $1597.00 plus shipping (yes, it is higher priced than another system out there but proper design parameters  require this)  Remember, with this or any other quality designed and built part, you will always get what you pay for, do not buy this component from the "lowest bidder".  Oh, and if you see a 4 air bag system for less-- thats just what it is!

Installation will take between 5-7 hours for both sides

Why consider a 4 air bag system?  Besides not having the original 2 sided air bag available, this "Q bag" system really is the "better mousetrap"

Three main reasons,

1. Safety-- if you blow a rear tire or one of the original style air bags of your rear suspension, you are stopped where you are.  There is no moving until you replace that tire or bag.  Tell me at 2AM, on the side of the highway with trucks blowing past you while you stand in the rain in an ant bed if this is an inconvenience.  With the new 4 air bag system, you can actually continue to drive carefully on 3 or even 2 rear tires and blow out 1 air bag on each side of the coach and still move to a safe place to effect permanent repairs.  Of course your system will be overloaded so please be careful and only do this as an emergency situation dictates. In effect, there is no need to carry a spare tire, if a front tire blows out, simply shift a rear tire up front and drive on to a local tire store. up on 5.jpg (69478 bytes)  Safety is the number 1 reason to have the quadrabag system.

2. Retrofit to new parts  As our coaches get older, so do its parts and the eventual shortage of the few specialty replacement parts that keep them on the road.  The original air bags are an exclusive component only available at a handful of specialty dealers and rather expensive.  This new 4 air bag system uses air bags that can be found on the shelf at most any RV dealership or supply store.  No need to pack away an extra air bag in your coach, no need to worry if you will find a new air bag when you need one, this new system does away with that worry.  Adapting to newer, higher quality production parts is always a good thing.

3. Performance  Not to say the ride of a GMC is not nice, as a matter of fact that is one of the great things of the coach but it would be nicer to have a bit more control, more suspension responsiveness without sacrificing the awesome ride we bought the coach for in the first place.   The new 4 air bag system does just that.  The difference in handling of a full sized stretch van and a mini van, your GMC will transform from a float like "marshmallow" feel to the responsive, sure footed and have the controlled handling characteristics many want today.  Not hard or bumpyor like riding a rail as some have said they experience with the old system, the new design (quadrabag) 4 air bag system gives you more control, better tracking and a sure feel without the rough ride.

And if all that isn't enough, it really looks cool too!  Update and upgrade your classic GMC to a better suspension system, install the all new "quadrabag" 4 air bag system, you will thank yourself.

Now for a few commonly asked questions courtesy of our good friend Rick Williams from up in the cold north country-- Michigan


1. Are there any changes to the leveling controls (in the wheel well)?
No Rick, the new 4 air bag system uses the original leveling system


2. Does it work will all leveling systems ( I have an electro level II)?
Yes, the new system will run on Power Level, Electro and Electro Level II systems, the new system actually will use less pressure than the original system.


3. Does it require compressor upgrades? 
If your compressor is in good shape, it will supply the new system fine (the new quadrabag system actually requires less pressure from the compressor than the original air bag), but of course original compressors are getting up there in age-- it would be a drag to have all of this new stuff air have no air cause that old compressor gave up the ghost!  It's always a good thing to have reliable components and the weakest part will be the one that leaves you.


4. What is included in the kit?
The kit includes, the 2 piece stationary structure (one for each side), 4 air bags and hardware, 4 arm risers and an air control manifold for each side.


5. Do we leave the manual shutoff valves that many of us have installed?  Why or why not?
The "air control manifold" replaces the air shut off kit from the original bag system and gives you shut offs for each bag for each side and a filler Schrader valve for each side.  This manifold will give you total control of the new system.

6. Does the "T" skirt still fit?  Yes Dave, you will need to modify the lower bracket a bit but it will work.

7.  Are the air line connections on the outside of the bag dangerous?  Let me ask you this-- if the original design has it's connection "on the outside"-- is it dangerous?  The Quadrabag" system has fittings just llike the original system.

8.  Does this air bag system make the coach ride rough?  More bag pressure relates to the "stiffness" of the ride.  The original air bag will bring the coach to "ride height" somewhere around 100 PSI.  The early 4 bag system will take more pressure than that, the Quadrabag system will take less than 100 PSI.  So, what would be the answer to the question? 


If you have any other questions, Email them to me & I'll post them.



The 26 foot, 12,000 pound Antique Hot Rod with Plumbing -- GMC Motorhome