I just joined this group and having read the existing posts I haven's seen this one. What can be done to tame the 21,000 lb air suspension on the freightliner when it is running bobtail and light (12,000 w/trailer)? I tried talking with Freightliner service but they didn't seem to want to help with the problem. Onexman..I know you work with volvo but air suspension is air right? any help out there?

trowe,
I have absolutely no experience but have spent a large part of the last several years studying this and other sites.. the term PING TANK seems to come to mind.. a rigid expansion tank hooked inline with your suspension.. it will not decrease your weight carrying capacity appreciably,but will make the ride softer.. as I understand it a small air tank (maybe 10 gallons)like the portable ones used to air up a tire, with the largest diameter connections practical is what you want. search on this site and google on the net and you will find a lot of information. here are a couple of links
oo landline

in my search I found this very good article by our pioneer Larry Z.. the interesting thing is that Warpath's avatar has changed to the new one.. I was kinda hoping for the nostalgia of the old one that was on there the first time I read it.LOL
Larry Z's article

BOTH links referenced above have a LOAD of good info that many of us would do well to review (or peruse for the first time). I even picked up a few more pointers that I either missed or forgot about (probably the latter). GOOD STUFF!
Gary

Thanks guys. I'll follow the links and get educated. Hopefully I can solve my problem. My co-driver will thank you forever if I do.

Lots of interesting information, but one that I'm wondering about (because I had considered doing it too), is the suggestion on OO Land Line of using one of the fuel tanks for water. Is that really practical? 120 gallons of water is going to weigh 1000 lbs. With both tanks full you will be fairly well balanced, but as you use water or fuel your center of gravity is going to shift significantly. I have seen a lot of discussion of front/back weights. How much thought has everyone been putting into side to side or corner balance?

Since it wouldn't actually be possible to reuse that fuel tank anyway (for fresh water, I suppose you could clean it and use it for gray), I thought about selling off the 120 gallon tanks and installing a pair of 75s instead. Even at a total of 150 gallons, that's pretty long legs when you're used to stopping every 300 miles or so.

I think you are overstressing the effect of a single 150 gal.(give or take) tank on the center of gravity. Around here there are a BUNCH of trucks running single 100-150 gal. tanks. The only thing countering it on the other side is the battery box. They have been running this configuration (usually pulling a 6000 gal. milk tanker trailer on dairy pickup duty) for about 20 yrs now, so if there are any negatives to this setup, either they don't care, or there aren't any. I wouldn't worry too much about it.
Also, even if you like to stop every 300 miles, it's still nice to know you don't have to fuel up every second or third stop. I think a 1500-mile range is kinda cool, and a 150 gal tank would be no sweat for a Class 8 pulling a 5er.

.....my 300 gallons gives me the opportunity to cash in on discounts and cheap prices....also to know that I will sleep all night without running out of fuel or weather out a storm in cool/ warmth without any thought of having to shut down the Onan generator....that my batteries will be ready in the AM when I start up the tractor engine...that anyone in the tractor will be cool/warm all nite-should they not wish to sleep in the trailer....That I can give assistance to a fellow RVer should he not be checking his fuel levels as much as necessary. That I am self sufficient no matter how bad the local situation is-that I don't have to stop in places that are weird/dangerous.....these are a few of the benefits of mass fuel tanks......and I can cheat now and then using some heating oil or Military fuel.....geofkaye

Spoken like a true gentlem- uhhhh, acquaintance.......

Gary, not sure, that's kind of why I asked. I do know that truck manufacturers relocate tanks to shift weight towards the rear. That, of course, is primarily an axle load issue. I suspect it also improves braking when running bobtail. On a toter configuration 1000 lbs could be 7% of your weight. I can't believe you wouldn't notice a difference in handling. For a conversion it's not as significant, as long as your do your homework on the rest of the design.

Geof, if you're driving every day, having $600+ tied up in your tanks is no big deal. For a casual RVer, I might not use 600 gallons in a year. So I only have to buy fuel twice a year? In between trips that fuel is going to be sitting there. That's not good for the fuel. I might save a few pennies on cheap fuel (right now there is a 10% difference in the highest and lowest prices at Flying J, and I happen to live in one of the lower states), but having my money tied up costs in other ways. Not to mention how volatile fuel costs are right now. Even with just a pair of 75s I could drive from KC to Vegas and likely have fuel to spare. 1500 miles gives me more than enough time to pick the right place to buy fuel.

Gypsy-
Keep in mind that just 'cause you have the capacity, doesn't mean you always have to use it all, all the time. Short trip (200 mi+/-), put in approx. 50gals.; long trip (1000+ mi), feel,uhh,fill 'er up!
I think you get the idea. It's better to have it and not need it, than to need it and not have it. Have fun!
Gary

....Gypsy....I hold a total of 449 gallons in 4 vehicles or $1059.19 worth of fuel if I fill them up all at the same time[$2.359]....[I just don't pay my employees for a week!] I shift fuel from one tank to another and from vehicle to vehicle....I try to buy as much fuel at as a cheap a price as possible whenever I get the chance....I add a little heating oil at $1.75 a gallon now and then as well as pump out some of the surplus fuel from the Army vehicles that come in with fuel in them.....we treat all our fuel with PowerService conditioner in the white bottle.....so far so good and we are looking in to re-refined oils from a supplier in Kentucky....for both "heating and off road fuels".....Bio is an option that Lykin's Oil has available and there are several others....I spend a little time each week on the fuel issue so it does pay dividends.....speaking of dividends....my 9600 shares of ExxonMobile is more than $60.00 a share on Friday.....huummm.....geofkaye

...._one_ other_ thing_....I have electricity if the power goes out....for more than a week+ in my house and there is the issue of heat and A/C also....[course my neighbors will be scratching at the doors.-the same ones that took me to court last Tuesday]....or I can just stay in the trailer for two weeks and be warm or cold-just NO cable tv and NO computer....might have to learn how to read books again [or run a rather large bill with the girlz].........geofkaye

Gary, my main reason for changing tanks is the original tanks will eat up all my basement storage. https://www.truckhome.com/infopop/emo...icon_smile.gif I don't want to hang out past the rear axle more than 6', so it's going to be a little tight under there.

And since I'll be changing a lot of the original factors the engineers used when they designed these trucks, I explore what effects changes will have. I'm shooting for a 25,000 lb conversion compared to the 80k the truck was designed for. There is a good chance I'll also be removing up to 600 lbs from the rear by changing out the duals for super singles. To be honest, I'm considering changing my mind on using aluminium for the RV frame because I'm worried I might not have enough weight to soften the suspension. IE. the whole ping tank problem that started this thread.

And FWIW, I think a poly tank would be a better solution for fresh/gray water anyway. It can be formed to use space that otherwise might not be useful. I'm hoping the numbers work out to fit a pair of 120s behind the rear axle, partially pushed up between the frame rails. There's no way you're going to put potable water in a used fuel tank, I'd even be hesitant to use a new one if I wasn't sure I could get it clean. And if you use it for gray it's going to be a pain to dump unless you move your toilet and black tank near it.

-lee

....potable water in a aluminum tank will be a problem....TASTE....but if you were to line it with a plastic bladder maybe you won't have that problem/or maybe you are just switching it to another problem....also there is the freezing issue. I drink only bottled water when I'm camping....I had travelers diarrhea in Fla. one year for the whole Christmas vacation because of bad water in the water system on the island-I was told!....Also! Liquid has a movement issue you also have to take into consideration....sloshing can cause loss of control if far away from the axel and/or will act as a counter weight....Ever drive a tanker?....or a sewage truck half full?....interesting!....There are fiberglass tanks made currently-I don't know the manufactures name- that make fuel tanks for off road equipment that are not standard shapes and fuel tanks for boats that are different sizes and shapes[TEMPO] available from any marine dealer....just a few options/suggestions off the top of my head...HTH....geofkaye

BIG 10-4 on the sloshing liquid issue. Ever seen a milk truck when it stops? These tanks have NO baffles in them, or else they would have a load(like 6000 gallons)of partially-churned butter when arriving at the milk plant. When the truck pulls into our dairy farm to pick up the milk, even with the maxi's set the truck "rocks" back and forth for a few minutes. Probably not as scarey with 100 or so gallons, but I'm sure still a force to be reckoned with.
Just my .02.
Gary

Hello Trowe....If you want to Tame the Air Suspension on your Truck contact : Don Yale at Donvel...Web: https://www.donvel.com....He help Tame my Peterbilt....He works mostly with class 7/8 Trucks, but he also does some MDT's.....Great person to deal with and very conscientious.....He is located in Gladewater,Tx......Don's system works and it does not change the original Suspension Parts...He can help you with the Front Steer Axles, Cab Air, Rear Air Suspension and Air Ride Seats......Hope this Info Helps.......Jim

Now we can link to Donvel....(I didn't think you would mind).

Thank you Gary. I had heard of Donvel in relation to front suspension but didn't know how to contact them. Thanks for the info. I'm going to Texas for the winter so I'll contact them while I'm down there.

thom

Hey man, thank "jauth 1" one notch above. I just edited out the accidental "tail" that got stuck on the end of the address as he posted it. Glad to help, though. I hope you get all the info you need on air suspension foibles. I found the site rather interesting myself....

I just had the Donvel Air System installed at his shop 2 weeks ago.....I am a Happy Camper...It does Tame the Truck Ride....It will Never Ride like a Caddy...But it is not bucking me out of the seat when we hit a big dip ,railroad crossing or going over a bridge.....Big Improvement....A very Conscientius and honest person to work with....If you are not happy simply return and he will refund your money......We did a before and after test on a road by his shop...so you can tell the improvement right off the bat.....We also added Motion Controls on the Cab Air and the Rear Air bags of my Class6 Peterbilt.........Jim....Ps.Thanks for fixing the Post.......

Glad to do it! Actually I was curious to check out the site myself, and figured that was the best way for myself and others to do so. Thank you for the link!

Hi gang. I just received a "kit" from Donvel. It includes air bag suspension add ons for the steer axle and a set of control valves for the existing rear air bags and all the air line valves and gauges needed.. As soon as I can get to a place to do the modification I'll come back and let you know how it rides.

......excellent!....I'd always interested in suspension upgrades....geokaye

Is this Donvel's own kit or are they selling the Brock's "Add a Ride" kit? Sounds like a good deal either way; I'm just curious as to whether there was another player in the front air-ride market besides Brock's.

All I know is that the parts have a Donvel label and a patent number along with a statement that other patents are pending. I'm not familiar with Brock products. I got the valves installed on the rear and the front airbags installed except for the airlines. So far the process has been pretty straightforward except that two of the bolts in front are tough to get nuts on inside the frame. That might be different on other model trucks. The air fittings are push-on. Another couple hours to get the air lines run thru the firewall and mounting the gauges and I'll be ready to roll. It might be a few days until I can get back to it.

I have since checked the Donvel site; it is a different product than Brock's. The Donvel setup acts more to stabilize than to soften the ride like Brock's does.
On Brock's setup the rear of the front spring is disconnected and an airspring is installed between the rear of the spring and the frame, thereby relying on the airspring to fully support the load and apparently really smoothing the ride.
The Donvel system on the other hand is installed WITHOUT disconnecting any part of the existing spring, but instead uses an airspring to help stabilize the ride rather than soften it.
Each company is attacking a different issue:
Donvel- instability
Brock's- Rough or stiff ride

I hope this helps to explain things a little. It looks like either product should do what it is designed to do.

Gary

Here's an update. I got the parts installed. I found I need longer fingers and a wrist that bends in a few more places. The hardest part of the install is getting the nut on the bolt inside of the frame behind the exhaust on the curb side. I only had about 100 miles on the set-up when I blew one of the four airbags. The are Firestone products so I think I just happened to get a bad one... that would be typical for my luck. Anyway, the ride is definitely improved. I want to get a few more miles under my belt before making a full endorsement but first blush seems to indicate it's going to be money well spent.

.....we used to use that air springs on the back/front of stock cars for "wedge" adjustments it was easier that way instead of cranking up/down on the frame bolt to add/subtract wedge to the passengers side.....It was a good system and some even added a adjustment valve on the inside of the cab to make things work faster....I assume things are different now....we used actual car frames unlike stock cars now....we could adjust wedge and leed with a 3/4 inch air wrench or a rachet and air chuck depending on how far things were out......then again we races on dirt....not blacktop.....geofkaye

Here's an update on the blown airbag. I sent an email to Donvel on Sunday night about the bag. Monday morning I get a phone call from them. The bag will be replaced under warranty, no questions asked. As soon as I can stop my trip long enough to get the bag delivered I'll have it in hand. So far so good. They didn't even ask for the bad part to be returned. Maybe they will in the new shipment. It wouldn't surprise me if they did.

....didn't Firestone have a recall on some air bags some time ago?.....I don't know where to start to look....geofkaye

I don't know about any recalls. When I got the blown airbag off of the truck I discovered that it had contacted the exhaust and melted. A closer look during my installation would have caught the small distance. I have wrapped the exhaust with two layers of heat insulation tape so that should solve the problem. Donvel replaced the bag but requested that I return the old one. I did that with a letter of explanation about the installation. We'll see what they have to say but I don't expect to hear any more since nothing was said in their instructions about the exhaust being a problem. I now have a few hundred more miles on the Donvel system and I am pleased. I would recommend them for softening the ride. It's still a stiff suspension but the jolts are softer and don't rattle your teeth so much. It ain't a caddy after all.