Air bag suspension w/leaf spring mains (pics?)

[1x1_Speed_Craig]

Hi all,

I'm just finalizing an order with Martyn at AT for some Firestone air bags and upper mounting brackets, among several other things.

I'll be using the air bags for the suspension, and will main leafs from a set of new stock CJ-7 front springs to locate the axle only (I also plan on adding shocks). I also have CJ-7 main eye hangers and shackle mounts, but am open to doing something different if needed (read on...).

I have seen several people suggest using the "dummy" leaf spring to locate the axle, but have not been able to find any photos of such a set-up.

Does anyone have pics of a trailer running this air bag/leaf spring combo?

I mainly wondered about the following:

1. With a 2" budget boost and 31" BFG KM2s on my tow vehicle (and trailer), I planned on running spring-under on the trailer to best match the ride height. I may have to run spring-over to allow the air springs enough space for the full range of travel. I'm also wondering if the stock-height leaves will be adequate.
2. I'm wondering about clearance for the air bag diameter (mounted just inboard of the frame rail) between the leaf spring/U-bolt spring plate/etc. when compressed.

Any ideas, thoughts, and most of all PHOTOS are greatly appreciated.

Thanks,
Craig

 

[elmo_4_vt]

I haven't seen any pictures of that exact setup either. However, I think it would be hard to even use pictures as a basis for your build. If it's a custom setup like you'll have, it's very unlikely that you'll find something close enough to copy off of. At least in my experience, you'll just have to dive in and start taking measurements, probably make a mistake or two, and just keep going to fix things until they work correctly. At least that's usually what happens to me.

-

 

[dieselcruiserhead]

Pretty simple just 1 or 2 leafs to place it and that's it, with the airbag above. I was at harbor freight the other day and there was a very light duty trailer there with a single leaf that was brand new, nice and short. That would be a nice setup I figured for an airbag setup..

 

[1x1_Speed_Craig]

I haven't seen any pictures of that exact setup either. However, I think it would be hard to even use pictures as a basis for your build. If it's a custom setup like you'll have, it's very unlikely that you'll find something close enough to copy off of. At least in my experience, you'll just have to dive in and start taking measurements, probably make a mistake or two, and just keep going to fix things until they work correctly. At least that's usually what happens to me.

-

I get that...just trying to minimize the trial & error. I'm a planner by nature, and like to think things through thoroughly before executing.

Pretty simple just 1 or 2 leafs to place it and that's it, with the airbag above. I was at harbor freight the other day and there was a very light duty trailer there with a single leaf that was brand new, nice and short. That would be a nice setup I figured for an airbag setup..

It's really not that simple, though. See the bracket/air bag photo above. The diameter of the airbag will increase as it compresses, and clearance is needed to ensure the sides of the air bags don't get ruptured on the nearby leaf spring components. The assumption is that the airbag mounts will be welded to the side rails (vs. a crossmember). A crossmember mount may be feasible, though...again, I'm looking for design input.

I have seen a lot of people here suggest the idea of using this set-up, but it seems as though it's mostly general opinion vs. proven execution. I just want to get it right the first time, and want to consider any potential pitfalls before starting to assemble.

Craig

 

[Bullseye240]

The diameter of that bag will not incerase much as it compresses. Best bet is to put it between the main leaf and the frame. If the leaf is under it then it cant hit it.

 

[LandyAndy]

Some useful info on this site from the loooooow rider boyz.... :sombrero:

http://www.airbagit.com/category-s/1881.htm

Cheers,
Andy

PS... Why not just make a set of trailing arms, as per the AT trailers. It's only a bit more tube & some bushes. That's what I'm doing for my trailer, enough info & pic's available to guess't'mate a design that'll perform just fine.

 

[StumpXJ]

Not sure of any trailer pics out there, however you should find plenty of pics from the lowrider truck guys as noted. It truly is simple. I understand wanting to plan it out, but sometimes its easier to just get under there and see what will work. When you get it figured out, build it to suit. Unless someone has the exact trailer as you, it wont do much good. You have the concept, you just need to make it happen.

As for clearance, I made top brackets very similar to what you just ordered, and dont have any clearance issues, but I am running a trailing arm (similar, as it also has ubolts, plates etc). For the bottom brackets, I made something that looks very similar to a spring perch, only taller. Its welded straight to the axle, and the bag is mounted there, between the frame rail and axle. I also run the same firestone bag that Martyn (AT) uses. My ground clearance with 31 inch tires is 25" to the bottom of the frame rail. Not sure what numbers you are shooting for, but that seems to be a common number.

If when you get the parts you run into clearance problems, the crossmember point you made would negate any issues there, as you can move it as far in as needed. To echo what bullseye said, the bags dont get much wider that what you see pictured. You are never supposed to run less than 5psi in them, so they hold their shape.

One last thing to note, be sure to set your shackle angle with a "normal amount" of air in the bags so its at your normal ride height. I run usually 45-55psi in my bags, but it will obviously vary greatly. The other good thing about running a single leaf for locating the axle? If you ever damage a bag or air line, you will likely still be able to limp it to a repair place or home. My trailing arm set-up is a little different.... I have to rely on bump stops alone.

Here are a few pics of my set-up as I was building it, maybe something here will help?

here is one at ride height, just to give an idea.

~ James

 

[indiedog]

I would think the best arrangement is to have the bag directly over the axle so that it's a direct transfer of forces into the bag. If you fix the bag to the spring then the spring is doing a lot more than just locating the axle. I would also avoid mounting the bag forward or rear of the axle as that will make the axle twist also putting more forces into the springs.