Air Bags Air Ride

[TNTBOSS]

Hello, I am converting a GMC Topkick, I am making more of a lounger than a MH. I am using a Chevrolet Suburban, adding it to Quad cab of the topkick making a 6 door suburban on the topkick Chassi. I would like to use air ride on the body to gain a nicer ride than the topkick can give on its own. My question is what type of bag do i need? The truck has air brakes so the supply is not an issue. I have looked at some for as little as $79 each on "lowrider custom truck sites" Can these be used or is there a better bag or air spring to use?

[hot rod]

Go down to your local semi parts distributor. A lot of the class 8 semis have air ride cabs and have special small air bags just for that purpose. Ask them to browse the shelves and tell them what you are doing, you'll find it.

I have used those "lowrider" air bags you are talking about for exactly that, we used to do air ride suspensions. Those are way bigger and stiffer than you need for a cab.

[TNTBOSS]

Thanks Hot Rod! I'll do that. Any idea how many bags are usually on a class 8? Wondering how many i will need.Thanks again.

[Kenn]

My truck uses two small (4" D x 6" ? tall). It is an old Peterbilt and it pivots at the front of the cab on large bushings. The cab is only about four feet long and the travel is around 1 1/2". Are you going to make the cab and all of the body ride on air? I have seen trucks on the freeway with long sleepers that move with the cab and they have much more travel than mine. Good luck and put some pictures up as you go.
Kenn

[hot rod]

I am not familiar with the way they mount, or how many, as my experience on that lies with the lowriders. I found out about the cab air bags digging through the local semi place looking for odd sized air bags for custom suspensions. Small world.

Kenn has some good pics there and brings up a good point I had not thought of. The body will need to be securely mounted to the chassis in some fashion that keeps it from moving front to back and side to side, as the air bag gives no help in keeping the body located, but must still allow it to float up and down. The solid hinges on the front of Kenn's cab keep it located while only the back floats. You'll need to fabricate something very sturdy as that moveable mount is the only thing keeping the body on the truck. And you'll need a solid stop (like the shock in the photo, when it is fully extended) that keeps the body from moving upward too far on a bump and tearing stuff up. Also, keep a good inch clearance in all directions that could rub on the bag, you'd be surprised how much those things can balloon under compression.

And the more I think here, more things come to mind. If your body can move, any connections like wiring (easy) and plumbing (maybe a little harder) must also be built to flex as well. I don't know how much of that you will have with your type of build, but something to think about.

[40's rock]

I have a leaking bag on my rear axle. Unfortunately, International only has parts listings back to 1991, even on their tech line.
I will pull them off, match the width, height and rating...hopefully it will be an easy find.
Anyone have advice on which MFG to use? Tips?
I plan on using the take off bag that doesn't leak as a jack for my trailer. I will install some sort of quick connect valve (tire valve perhaps?)

[40's rock]

Well, it put up a valiant fight....but finally removed 28yrs worth of corrosion and crud...and one blown air bag.
Based on the dimensions, Firestone has a bag that matches every dimension, bolt, air line, etc. but is a little taller. So I am replacing both rear bags (the functioning one was apparently replaced less that 28 yrs ago..)

This is the good one, actually more of an airspring.

[coal]

You will need a torque rod to stabilize the cab side to side movement. Any cab sleeper air bag should work, get the mounts too, fittings etc and a levelling valve. Prob also have to build a subframe under the whole unit front to back.

[40's rock]

I am not adding air bags, I am simply replacing one that is close to 28 yrs old and another that is somewhat newer that are already on the back/RV portion of my rig.

It appears everything on the truck was well thought out/shop built....after 28 yrs, mostly parked, things need maintenance.

As a side note, http://www.fsip.com has a complete listing of all Firestone air bags, complete with PDFs and dimensions.

[philadelphia]

Originally Posted by TNTBOSS

Hello, I am converting a GMC Topkick, I am making more of a lounger than a MH. I am using a Chevrolet Suburban, adding it to Quad cab of the topkick making a 6 door suburban on the topkick Chassi. I would like to use air ride on the body to gain a nicer ride than the topkick can give on its own. My question is what type of bag do i need? The truck has air brakes so the supply is not an issue. I have looked at some for as little as $79 each on "lowrider custom truck sites" Can these be used or is there a better bag or air spring to use?

The larger the diameter the bag the less pressure it will need to support the load..Meaning the smaller bumps will be isolated better..Dont go too large as it will make the ride mushy when the bag is installed at the perfect ride height.

ON my build i have thought of four corner air bags with a simple 3 link suspension to support the cab and sleeper.That with dual watts links to support it from side to side movement and after that i would have needed two anti sway bars as well.

I opted for pivots up front and bags out back with a panhard bar.Im quite happy with it and the truck rides just as well as a late model caddy.

I used two double convoluted 8" diameter bags and 14-16 psi seems to be the sweet spot.