The Stovebolt Site Forums The Parking Lot Big Bolts rear air ride

I am lookng at putting rear air ride under my 57 LCF crew cab project. Is there any advantage to looking for front air ride also or is rear going to be enough to smooth out the ride? I have seen some kits out there for front air ride. The rear suspension is used out of an 06 freight liner. I really have no experience with air ride but people keep telling me that it will be a kidney buster when it is not hauling my 5th wheel and it may be a little rough with the 5th wheel. Its a gmc w4500HD chassis that I am using and the rear seems really stiff.

If the bags are a "rolling" style, it will ride fine. If they are still the "convoluted" style it will right stiff. I would think that an 06 Freightliner would be rolling. The leveling valve will determine the pressure to maintian the height. Less weight, less pressure. Got a pic you can post ?

Does your LCF have an air compressor on it? If the suspension is from a class 8 Fliner it will use a lot of air. Installing air ride will help. Air ride on the steering axle is not very feasible. GMC tried it in the 60's and it was a disaster and I haven't seen anything that really works. Putting air ride on the back of the cab reduces the back slap a lot, but it requires a tilt hood such as modern trucks have. An air ride seat with an isolator will help a lot. But for the most part, a short wheel base LCF will ride rough. Most of the kits I have seen don't have a leveling valve, and air must be regulated manually to compensate for difference in load.

I do not have a pic. From what I know it is the rolling style. I wont pick it up for a couple weeks. I am going to use the leveling valve for the air pressure. I am thinking of an electric pump with a tank so I can supply enough air.

The electric compressor should be able to keep up with it, once the bags are inflated. It may take a few minutes when putting a load on. The leveling valve has a built-in delay so it isn't constantly deflating/inflating from suspension movement on the road. You will need to use the panhard bar too to keep the axle centered in the chassis. The compressor only needs about 80psi capability. My Pete will get to 70lbs bag pressure with an 80,000 load, so I don't see yours getting close to that. Maybe 35-40 lbs with the trailer on.

Bigdreamer,
Do I need an air tank or is just a compresser enough. My thought was with tank, I would be more relying on the tank for the pressure changes and the comprressor to keep the tank pressurized. Plus then I could also have some rediculously loud air horn for the idiots that always seem to cut in front of me at the last second.

Yes, you definately require a reservoir.You may have some confusion as to what a leveling valve does based on your statement "I am going to use the leveling valve for the air pressure". It's job is to provide an amount of air to the bag that will maintain a ride heigth and equilize both sides of the axle. When one side is depressed air will flow to that side to increse the heigth. The system pressure is maintained by a regulator and the reservoir will need a relief valve and the lines need a one-way check valve in case of a loss of air. You may be able to get all of that from the f-liner. As you can tell all of them have different functions but it's fairly simple.I don't know about the conventional cab/chassis but I would think they have about the same rear axle setup as the cutaways have. I had a 07' 4500 box van and it rode very well. Surprisingly well in fact. So some of it may be in what your expectations are. Something to consider. The rear springs on the newer trucks are much longer than what your (57'?)LCF was built with. That would be worth investigating if you haven't committed to the air setup. Good Luck regardless and Happy Thanksgiving.

53moneypit, I may not have the terminology correct on the leveling valve...by pressure I meant the amount of air in the bags. This is all new to me so thanks for helping me out on this. My chassis is an 03 GMC W4500hd and the suspension is really stiff in the rear. I will never have a load on it with the fifth wheel trailer like it was intended as a box truck. the tongue weight of the fifth wheel is only around 2000 lbs.

While installing air ride is doable, it would involve quite a bit of work. I certainly would consider softer springs. For air ride you would need an air compressor and a reservoir. The leveling valve maintains constant ride height by inflating and deflating the bags as needed.

And you need to measure to see if you have enough room for everything. I have several F-liner cut offs that I bought for the 3rd members. There's a lot of bulk there to squeeze under an LCF.

At this point Its just a little more fabrication. I am moving the axle back 8" anyhow so I have enough room for the fifth wheel to turn 90 degrees with out hitting the cab. I would of had penty of room but I scretched the cab 38" to make it a crew cab. I will already have all the spring bracects and crossmembers out to move it. How/where could I find info on softer springs? How do I determine what I currently have? I guess I could pull out some of the leafs.

If you have the frame rails stripped, you have done quite a bit of the work. However, you still need to make sure you have room on your axle housings to mount the Airliner suspension and make sure your frame web is tall enough. As for springs, the front springs from a set back axle class 8 truck make pretty good springs for the rear of a lighter truck. They are longer, wider and have only 3 leaves. International 9100, 9200 and 9400 from 2000 on up use front springs that work well for this kind of setup. They use a dry bolt bushing which makes fabricating a spring hanger easy. Pulling some of the leaves of an old shorter spring usually doesn't accomplish much except invite broken leaves.

I used to sell and install air tag axles on grain trucks built by a company in IA called Silent Drive, 712-737-4865.The part that would be of interest to you was a 12V-DC compressor in a steel frame mounted box that proved very successful. Over a period of several years I never had to repair or replace one. It would be perfect for your application. A standard trailer air reservoir is what I used and would mount it on the front crossmember.It was the best setup I ever found for adding an air suspension to a hydraulic brake truck. You may want to give them a call and see if they still offer it.

I had forgotten about Silent Drive. A guy named DeJong started building those things about 40 years ago and it is still a family operated business. I think buying a kit from them would be a lot more feasible than trying to modify a class 8 air ride. They used to be dealers for Link cab air ride. They might offer some ideas about that.

I remember seeing the thread about you stretching the cab into a crew cab. I haven't seen the pictures of how it all turned out, but if those first pictures are any indication of your fabrication skills, in my opinion, you sir can put a class 8 air ride under a Chevette. I wish I had your skills. Keep us up-to-date, as I thought about this exact same swap before I found out how good my truck ran and drove.
Scott

Scott, thanks for the kind words. I have no doubt I can do it either. I Like the idea of spending 1/4 of what it would cost for a "kit". I am moving along good with the cab. It should be finding its way onto the chassis pretty soon. I just finished all the under cab bracing and mounts. Now I am scraping this tar like undercoating so I can get some paint on the underside before it goes on the chassis. check out the progress
http://rides.webshots.com/album/580587250vqfuun

I was away for the holiday and didn't get any email notifications for this thread. Looking at the project as a whole, I would be tempted to remove some leaves and use "leveling" air bags for the extra weight of the trailer. They just sit between the spring pack and frame and only come into play when weighed down. I think it would be a much easier route than fabricating the F-liner suspension to your axle.
It IS gonna look VERY unique when done.

Buggy5872 amazing work on the cab. Can you give me some insight on why you had to cut the roof off on front cab. What did you go back with for the roof? Also when you put the " B" pillar in did you have to put additional bracing in the interior to stiffen the roofline? Look like you are on the home stretch . Good luck in finishing the project

Bigdramer,
My springs pack consists of 6 leaves and 2 overload leaves on top of the springpack that only come into play when it is weighted down. Should I remove 2 to 3 leafs and leave the overload leafs on? Or remove the overload too and get the air helpers?
thanks
Shane

49bourbon,
I used the original LCF cab, a conventional cab and a panel truck. The roof and b pillar is off the panel truck. I flipped backwards the door jamb I cut off the original lcf cab and used it as the back of my b pillar. The inside of the b pillar is what was there from the panel so it is completely boxed in. I also boxed the bottom of the b pillar that is below the floor in between the steps. Under the cab, I continued the c channel bracing that lcf cabs have all the way to the rear mount. I also added a cab support that will mount to the frame in where the two pieces of c channel mate together in the middle of the cab. Not sure I need it because I just have the rear and front mounts bolted to the dolly I made and there is no flex at all in the cab. I even jumped up and down inside the cab and could not get it to flex. I tend to over engineer things. I would be mad if the cab started sagging at some point. let me know if you have any more questions. On a scale of hardness from 1 to 10 I would give this a 12.
Shane

LOL on the difficulty level. What you do depends on what you want for a ride. Are you only concerned about the ride with the trailer on or for bobtail too ? I would remove the overload springs either way and let the air bags support the trailer. They are rated for 3500#. I would still use the electric compressor, reservoir tank and a leveling valve, rather than inflate manually. You will get a better ride. If you want a softer ride bobtail, then I would remove a couple of the main leafs too. All the add on kits I've looked at are the convoluted style and not my first choice. They ride harder than the rolling bag style. You may be able to fabricate mounting plates and use the rolling piston bags, reservoir and leveling valve from the Freightliner instead. The issue with them may be height. They may be too tall to fit between the spring and frame.

thanks for your response. I am looking for a decent ride both ways. I am still undecided as to what I am going to do.

One can just remove stock leaves to get the desired ride, longer leaves in front as has been mentioned before softens ride, Kelderman has air ride kits that can give one ideas for making your own. For occasional use w/ an electric compressor, install a shop air fitting(schrader) to fill up bags if they get totally deflated, or for working on system. I made my own parallel 4 bar system using trailer torque rods, reasonable price, 2 bags off a semi 4 bag system. http://rides.webshots.com/album/581681868MDNTHo

http://rides.webshots.com/photo/2846914230107333904ittnNt