Air Bags - What Do They Do?

[mrxlh]

Hello and welcome to the forum. Just a reminder that installing air bags will not increase the towing capacity of your Dodge or any other truck.


While that statement is true, it is only half true.

Air bags will not increase the payload capacity of the rear axle of the tow vehicle, however they can be used to get your pin weight correct and transfer weight (nose down) back to the camper axles.

In essence, air bags work very similar to a WDH.

[SteveC7010]

In essence, air bags work very similar to a WDH.

Sorry, Ryan, but you are not correct here.

Weight Distributing Hitches use the fulcrum and lever principle to transfer tongue weight back to the trailer axles and forward to the front axles of the tow vehicle. Properly installed and adjusted, this will level out both the trailer and tow vehicle. It will also correct the imbalance of weight ratio between the front and rear axles of the TV caused by the extra weight of the trailer tongue on the rear of the TV.
http://www.etrailer.com/Merchant2/graphics/00000001/pics/f/a/FastwayE2WeightDistribution.jpg

Air bags simply raise the rear end of the tow vehicle. There is neither lever nor fulcrum to transfer weight forward or backward. They will level out the tow vehicle, but the weight remains where ever it is.

Air bags can not improve the weight carrying capacity of a truck because they do not bolster springs, axles, frames, wheels or tires. All they do is raise or lower the rear of the truck in relation to the ground.

[mrxlh]

I have had air bags on my trucks for 5 years now. You are incorrect.

There is no difference between a WDH and air bags, the only thing you are physically changing with WDH and air bags is the height between the axle and frame. Thus leveling the vehicle and trailer. Which no matter how this is achieved, you still transfer weight to the front of the vehicle and to the axles of the camper.

If your assesment was correct, simply airing up my air bags would have not changed the tension on my WDH. However it did so much that the tension was not there at all, hence no longer the need to use them.


As far as your statement about air bags not increasing the capacity of the springs, that is dead wrong, so much that most newer semi trailers do not use springs at all any more and use strictly air bags.

The secondary reason for air ride suspension in class 8 trucks (primary is much better ride) is it is far easier to change ride height of individual axles to achieve correct axle weights than it is to slide axles and hitches around.

[SteveC7010]

edit - back in the game.

[JimEli]

FWIW, air springs using air pressure height control to compensate for loading is exactly how the suspension on a semi rig works.

[Bob Landry]

Steve is correct. Airbags do nothing more than raise the rear of the TV for asthetic appearance and to keep the rear from botoming out with heavy loads. They do nothing for weight distribution forward or to the rear. A trip to a Cat scale will verify this. Hitch your trailer and weigh the front axle with no WD, airbags deflated, then inflated. You are doing nothing to alter the weight on either axle, you're just making for a cushy ride.
As far as the big trucks, air suspension can lessen the rough ride for the contents in the trailer, but I fail to see how changing the height of the load shifts ant weight or has any effect of the load on the axles.

[Festus2]

"Just a reminder that airbags will not increase the towing capacity of your Dodge or any other truck" (Festus2)


While that statement is true, it is only half true.

Air bags will not increase the payload capacity of the rear axle of the tow vehicle, however they can be used to get your pin weight correct and transfer weight (nose down) back to the camper axles.

In essence, air bags work very similar to a WDH.

In two provincial government publications, both issued by the Ministry of Transportation in BC and Alberta in their Recreational Vehicle Towing Guide it states:
"Adding components such as air bags or overload springs does not allow these ratings (GVWR and GAWR) to be increased or exceeded". (p.7)

To me, this means that regardless of whether the weight may be transferred from one place to another, the weight is still there. Just because some of this weight may or may not be shifted to the rear camper axles, does not mean that this weight has been reduced and you can now therefore increase your payload.

[SteveC7010]

I have had air bags on my trucks for 5 years now. You are incorrect.

Your usage of air bags is noted, but your understanding of what they do is still not right.

There is no difference between a WDH and air bags, the only thing you are physically changing with WDH and air bags is the height between the axle and frame. Thus leveling the vehicle and trailer. Which no matter how this is achieved, you still transfer weight to the front of the vehicle and to the axles of the camper.

Here, you are confusing changing height of the rear of the tow vehicle with weight distribution. It's all about the weight on each axle. Raising or lowering the nose of the trailer/rear of the TV does not change one pound of weight on any of the axles. There is no weight transfer along the frame of the TV to the front axle.

If your assessment was correct, simply airing up my air bags would have not changed the tension on my WDH. However it did so much that the tension was not there at all, hence no longer the need to use them.

When you aired up, you changed the dimensions of the triangle created by the weight arms, the chains, and the A-frame of the trailer. Of course the chains came loose. What you fail to consider is that when you did that, you also removed several hundred pounds of weight from the front of the tow vehicle and from the axles of the trailer. By inflating the airbags, you disabled the WDH, returning full tongue weight to the hitch ball.

Now, before you try to tell me I am wrong here, this is easily proved. Put your rig on a scale with the WDH fully engaged and then air up, loosening the chains. The scale can't lie - the weight on the rear axle of the tow vehicle will increase and the weight on the trailer axles and the front axle of the tow vehicle will decrease.

Here's the kicker. Without the fulcrum and lever action of the WDH, there is no weight transfer forward or backward from the hitch. The WDH systems use the same principle as a wheel barrow. Lift the handles and weight comes off the rear stands and onto the carrier and the front wheel.

There is not a single WDH system on the market that does not use some form of the lever and fulcrum principle to do its job.

You want to really prove this to yourself? Hook up your trailer and TV without any WDH and put the rig on a scale, measuring the weight on the front axle of the TV, the rear axle of the TV, and the trailer axle(s). (Trailer singles or tandems doesn't matter as it is a single unit.) Then air up and read the three weights again. There won't be any difference, guaranteed.

As far as your statement about air bags not increasing the capacity of the springs, that is dead wrong, so much that most newer semi trailers do not use springs at all any more and use strictly air bags.

The secondary reason for air ride suspension in class 8 trucks (primary is much better ride) is it is far easier to change ride height of individual axles to achieve correct axle weights than it is to slide axles and hitches around.

I will concede that airbags will give some increased capacity to the spring portion of the suspension. But what they will not and can not do is increase the payload capacity of the vehicle. That is not determined just by the springs (and airbags) alone. Axle strength, frame strength, wheel and tire ratings are all portions of the ratings. If you increase the spring capacity, you are still limited by what the wheels and tires can bear. The wheels are usually stronger than the tires so the load ratings of the tires ultimately set the max. That fact alone tells why DRW trucks have much higher ratings than SRW's.

So, no amount of airbags will increase the payload capacity of any given vehicle beyond the load ratings of the tires.

[CarKath]

I have to jump in here. You guys are so off base on so many levels. Your all hung up on GVW's. Important ......yes. But lets look at this from an angle that may help everybody come together.

I will use example numbers and senerios.

For example- total gross truck can carry including 5th wheel trailer= 24500lbs

Truck total carrying capicity/gvw= 10000lbs lets say 4000 front and 6000 rear axle.

total trailer can gross=15500lbs basically 7500 each axle.

Going by total achievable gross for truck and trailer......... it does not work.
10000+15500=25500lbs

It does work however if you stay under the total achievable weight.

Not as hard to do as one may think.

The sticker on door post tells you exactly what your truck can do.

Sticker on your trailer tells you your axle weights as well.


Now let me say this. I was personally legal by virtue of what my TV can do.

But I was over on TV gross. I was 10200 instead of 10000 as per spec.

I was able to move this weight and under 10000 on truck. I am also 3000 under total gross TV can handle.

To say total weight is all that matter is wrong. It is all about where it sits and what total your truck can handle.

In your truck...........I mean specs for exact truck you have.......... not a generic I have a dodge 2500. That truly means nothing....... configuration of that tv means everything and it capabilities.

regular cab? extended cab? quad cab? all have different gvw's. Let's all compare apples to apples and let's all stop the blanket statements on gvw issues. It all about configuration.

Bottom line.........your TV determines your total gross. TV and 5th wheel trailer or TT. there are different gross weights for both

From there it comes down to axle weight and where and how you move it to where it needs to be.

Edit: just to add. My truck is stock. I have no after market systems installed. Weight can be moved in other ways.

[hankaye]

Howdy All;

My impression on air bags is they soften the bumps when ya drive.
With or without the trailer attached.
Most Semi trucks have air bags. They don't increase the weight for anything. They help improve the ride for the cargo and oh, yea. the guy up front as well...

hankaye

[JRTJH]

Against my better judgement, I can't resist commenting on the speculations of those who believe that helper springs or air bags "increase" their payload. Whether it is by "transferring weight" or by "lifting frames" or by "adding to the WD hitch angle" It's simply stated that air bags soften the ride but do NOT increase the GVW rating of the vehicle or the axle on which they are installed.

The Firestone Ride Rite installation manual has the following warning:

For your safety and to prevent possible damage to
your vehicle, do not exceed the maximum load
recommended by the vehicle manufacturer (GVWR).
Although your Air Helper Springs are rated at a maximum
inflation pressure of 100 psi, this pressure may allow you
to carry too great a load on some vehicles. It is best to
have your vehicle weighed once it is completely loaded
and compare that weight to the maximum allowed. Check
your vehicle owner’s manual or data plate on driver side
door for maximum loads listed for your vehicle.

I'd think it pretty clear when the manufacturer of the product states "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW" that they are saying: "AIR BAGS DO NOT INCREASE GVW"

Firestone does not compromise and say that if you have a 3/4 ton truck that has the same axle and brakes as some other vehicle that "it's OK" to fudge, they simply say "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW"

Seems pretty clear to me, crystal clear even....

Let the flames begin <sigh>

[Jim W]

I agree with the above poster 100% and have stated the same information from time to time.
What is lacking in a lot of people lately is common sense. Maybe this has to do with no shop classes in High School any more. I do not know why but it is becoming this way more and more.
Jim W.

[msp2jxr]

Both sides of the the issues on air bags have their merits. Try this as an example... Take a see see saw and put a weight on it and level it. It will take minimal FORCE to keep it level and can even be balanced in some applications.. If the balance becomes to far off center the force it takes to keep it from going down or up becomes greater, the weight is still there. Your trailer wheels and your truck is NO different. If your trailer is off balance your TV WILL work harder... your suspension will be either bottom out easier or be over sprung putting more FORCE on the wheels. Do not get Force and weight mixed up. Do not over think this.

[smiller]

I'd think it pretty clear when the manufacturer of the product states "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW" that they are saying: "AIR BAGS DO NOT INCREASE GVW"

Firestone does not compromise and say that if you have a 3/4 ton truck that has the same axle and brakes as some other vehicle that "it's OK" to fudge, they simply say "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW" Not a flame, but really, of course they say "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW", that boilerplate is always going to be present on any aftermarket towing equipment. It's meant as legal protection and often has little to do with anthing else. Even if a manufacturer had engineering data that suggested otherwise they would still print "DO NOT EXCEED THE VEHICLE MANUFACTURER'S GVW" on every piece of paper they could. It's just the way business is done.

That said, yes, it is always good advice to stay within ratings and the above is not meant to imply that you should ignore them, but life is a little too complex to be dictated by legal boilerplate. If it were otherwise I'd never touch a ladder! :D

And to the original topic, no, of course air bags do not do a thing to increase load capacity. I'm not sure why anyone would imagine they would.

[mrxlh]

112 gallons of fuel and 100 gallons of water center of gravity moved 3 inches in either direction from level changes your pin weight and your front and rear axle weight, end of story. Add any grey water or fuel in the fuel station in the rear and it gets even more benificial to level out the TV and the Trailer.

I have yet to come across a WDH for a 5ver yet, so I guess my air bags will just have to do.

[fireidiot]

Sorry to resurrect an old thread.

I am considering adding air bags to my 1500 Sliverado Z71 for my TT. My question is, if adding the bags will raise the rear end of my truck, does my Equalizer WDH need to be adjusted?

I just changed over to a new TT recently and I am unsure if my WDH is set up correctly due to rear end sag. I am going to check the hitch again, but was thinking about adding air bags to soften the ride a bit. If I get on a real bumpy road, the ride gets a bit rough.

[CarKath]

Airbags will not correct an overweight problem. Nor add to your GVW.


I don't know if your trailer is heavier than your truck can handle, but it sounds like it.

What trailer did you buy?

I am confident others will be able to add here once more info is given. Explain your exact configuration and I am sure you will get your solution

[rhagfo]

Sorry to resurrect an old thread.

I am considering adding air bags to my 1500 Sliverado Z71 for my TT. My question is, if adding the bags will raise the rear end of my truck, does my Equalizer WDH need to be adjusted?

I just changed over to a new TT recently and I am unsure if my WDH is set up correctly due to rear end sag. I am going to check the hitch again, but was thinking about adding air bags to soften the ride a bit. If I get on a real bumpy road, the ride gets a bit rough.

The answers to your questions would be Yes and Yes. If you inflate the bags and raise the hitch the bars will need to be retensioned. Otherwise you have shifted more weight to the rear axle even though it sits higher. In inflating the bags you have reduced the amount of tension on the bars, and therefore reduced the amount of weight moved to the trailer axles and the TV front axle!

[fireidiot]

The answers to your questions would be Yes and Yes. If you inflate the bags and raise the hitch the bars will need to be retensioned. Otherwise you have shifted more weight to the rear axle even though it sits higher. In inflating the bags you have reduced the amount of tension on the bars, and therefore reduced the amount of weight moved to the trailer axles and the TV front axle!

Thank you! That's kind of what I thought. I have an appointment next week to have my dealer look at my hitch.

[CampDestinations.com]

I'm an advocate of using airbags, but know they don't increase any of the weight ratings. One thing I have noticed though, measured through the use of my Sherline tongue scale (everyone should try to get one of these,) is that if I raise or lower the height of the trailer hitch by only 2" in either direction, the weight at the hitch varies by as much as 150lbs. Airbags help me "tune" the weight I put on the hitch ball before I even apply the WDH. For me, the biggest benefit of the airbags is the reduction of body roll and sway in my 1/2 ton.

[richf28]

I too have airbags on my half ton. I can tell a difference in the amount of sway since I installed them. I have tried different presdsures and have actually been able to see the difference in handling with even a 10 lb change in pressure.

[azlee56]

this is interesting. I read you all and then ask the bf (he hauled for oil companies) what a "payload" meant because when I talked to truck drivers I thought it meant something else and the bf assumed you all meant the gross weight on axles. For the life of me I am not getting this stuff. I sent my weights to one of you in a private message but never heard back but I am a little timid putting it out there for all to mull over. BF says we are good and so does all the friends, but I get nervous on stuff.

Keep up this debate, maybe all this will sink in my head yet!!! :banghead:

[azlee56]

ps. I am really impressed what the air bags did on our truck, but man if you aren't towing it makes a ride stiff.

[SAD]

...I sent my weights to one of you in a private message but never heard back but I am a little timid putting it out there for all to mull over....

A little timid? It's not like it's your social security number and date of birth.. If you've got questions about your weights, post 'em up!

[CampDestinations.com]

ps. I am really impressed what the air bags did on our truck, but man if you aren't towing it makes a ride stiff.

Deflate them. You don't need lots of psi in them when not towing or hauling. Some do have a minimum psi, like around 10psi, but that shouldn't make the ride very stiff.

[rhagfo]

this is interesting. I read you all and then ask the bf (he hauled for oil companies) what a "payload" meant because when I talked to truck drivers I thought it meant something else and the bf assumed you all meant the gross weight on axles. For the life of me I am not getting this stuff. I sent my weights to one of you in a private message but never heard back but I am a little timid putting it out there for all to mull over. BF says we are good and so does all the friends, but I get nervous on stuff.

Keep up this debate, maybe all this will sink in my head yet!!! :banghead:

I have posted my numbers in a couple of threads, I run about 900# over GVWR but well under GAWR, so don't be bashfull

[azlee56]

I leave the airbags for him to mess with, so he knows what is going on with them at all times. Right now they are aired up because we just came back from a trip. Glad he didn't take the air out because I went and got some bricks that is super heavy. We keep about 7lbs in it when we aren't pulling (I think is what he said).

Ok, here it goes.....now if you will be so kind and tell me how you all get from these numbers what is safe and what is ok but remember to stop in time. ;)

2008 3500RL Montana
shipping weight 11920
carrying cap 3560
hitch 1980

Truck ford 2000 250:
7.3l 3.73 tranny
gvwr: 8800
rear gawr: 6084
front gawr 4550
Towing package
drive 60mph - 65mph only and on flat land

[azlee56]

lol, I'd probably be more at ease pasting the other stuff. I cringe when you all tell ppl not to pull with their vehicles and they just spent a wad of money on the trailer! That is the timid part....but that is ok, I can bear good or bad news. honest :-)

[jsmith948]

azlee 56

Relaaax! we are all friends here! "bouncey:

[rhagfo]

I leave the airbags for him to mess with, so he knows what is going on with them at all times. Right now they are aired up because we just came back from a trip. Glad he didn't take the air out because I went and got some bricks that is super heavy. We keep about 7lbs in it when we aren't pulling (I think is what he said).

Ok, here it goes.....now if you will be so kind and tell me how you all get from these numbers what is safe and what is ok but remember to stop in time. ;)

2008 3500RL Montana
shipping weight 11920
carrying cap 3560
hitch 1980

Truck ford 2000 250:
7.3l 3.73 tranny
gvwr: 8800
rear gawr: 6084
front gawr 4550
Towing package
drive 60mph - 65mph only and on flat land

So if you were to scale it with the trailer attached, you are likely well over GVW, but likely within GAWR.
As stated earlier while 900# over GVW with three adults and two dogs, I still am over 1,000# under my rear GAWR.
As I stated in an earlier post I believe that the stock 235 HP rating of my 2001 Cummins has a lot to do wit the 8,800 GVW of my truck.

[azlee56]

been away to the mountains for a couple of days. I sighed a breath of relief, but what you all said that insurance companies can deny on the load stuff really sent me to thinking.


I do like the airbags (back on topic), I had gotten those bricks and so he could reach to unload them he let the air out of the bags (not all the air) and said it dropped the truck like 3 inches. I didn't realize those bricks were that heavy. Heavy yes, but not that heavy.

[TDF5G]

This what I found on the Air Lift website, They claim air bags do distribute weight and increase spring rate.

Air Lift air springs help:

Eliminate squat – Proper weight distribution to all tires eliminate squat and improves steering, braking and tire wear.

Improve headlight aim – Only level and stable vehicles provide safe and proper headlight aim which is critical for driving safely at night.

Increase handling and ride quality – Air Lift’s progressive spring rate absorbs road bumps and keeps your tires on the road for better handling.

Reduce bottoming out – Air Lift air springs restore normal ride height, reducing suspension wear and eliminating bottoming out on road bumps.

Control sway & body roll – Air springs increase spring rate and vastly improve vehicle stability. When towing a trailer, the air springs maintain your vehicle’s height which reduces trailer sway. Less roll and sway means a safer and more comfortable ride. This is also critical for motor homes or pickups with slide-in campers. These types of vehicles have a high center of gravity and a large surface area, and are heavily impacted by strong winds.

Now this is me talking; If you raise the rear of a 4 wheeled vehicle (truck, car, van, bus, motorhome, tractor, lawn mower, atv, golf cart, kiddie car, etc,) by whatever means, such as a WDH, air bags, a jack, a crane, or laying under the bumper and bench pressing it yourself, it seems to me that you will lower the front of the vehicle. Wouldn't that shift weight from the rear wheels to the front wheels?

[SteveC7010]

Raising the rear end with air bags does not change the amount of weight on that axle. It also does not change the weight on the front axle. It only levels out the vehicle.

[rhagfo]

I have had air bags on my trucks for 5 years now. You are incorrect.

There is no difference between a WDH and air bags, the only thing you are physically changing with WDH and air bags is the height between the axle and frame. Thus leveling the vehicle and trailer. Which no matter how this is achieved, you still transfer weight to the front of the vehicle and to the axles of the camper.

The statement above is totally wrong.
The spring arms in a WDH work much like lifting the handle on a wheel barrow, you are now sharing the weight that was on the legs, between the handles and front wheel.

The best demonstration of this I have ever seen was back in the late 60's when they installed a WDH on an Oldsmobile Tornado, then removed the rear wheels and the WDH held the rear of the car in the air.

If your assesment was correct, simply airing up my air bags would have not changed the tension on my WDH. However it did so much that the tension was not there at all, hence no longer the need to use them.


As far as your statement about air bags not increasing the capacity of the springs, that is dead wrong, so much that most newer semi trailers do not use springs at all any more and use strictly air bags.

Not increasing the springs, they don't increase the GAWR nor do they add to the weight the axle can carry.

The secondary reason for air ride suspension in class 8 trucks (primary is much better ride) is it is far easier to change ride height of individual axles to achieve correct axle weights than it is to slide axles and hitches around.

Steve is correct. Airbags do nothing more than raise the rear of the TV for asthetic appearance and to keep the rear from botoming out with heavy loads. They do nothing for weight distribution forward or to the rear. A trip to a Cat scale will verify this. Hitch your trailer and weigh the front axle with no WD, airbags deflated, then inflated. You are doing nothing to alter the weight on either axle, you're just making for a cushy ride.
As far as the big trucks, air suspension can lessen the rough ride for the contents in the trailer, but I fail to see how changing the height of the load shifts ant weight or has any effect of the load on the axles.

All air bags do is level and soften (smooth) the ride. They do NOT move weight around, nor do they change the GAWR of the truck.

[TDF5G]

OK, if airbags level out a vehicle, that would mean the rear is raised and the front is lowered. So how would that not move some weight from the rear axle to the front axle? Or are you saying the front is not lowered after raising the rear and the front stays at the same height as it was before?

[sagebel]

I use my air bags to level the truck once loaded +1" and then hook the trailer and set the WD bars. Keeps the headlights on the road and takes out any bounce/seasawing. It would be interesting to see if any weight is transfered front to rear with the bags inflated. If I have time I'll try it the next time I am at the scales.

[Jim W]

OK, if airbags level out a vehicle, that would mean the rear is raised and the front is lowered. So how would that not move some weight from the rear axle to the front axle? Or are you saying the front is not lowered after raising the rear and the front stays at the same height as it was before?

You may need to do some physics to understand this correctly.
Remember Newton's third law: For every action, there is an equal and opposite re-action.
What this means is when towing a trailer there is the mass of the trailer (pin weight, tong weight) which is pushing down on the rear axle, springs, wheels and tires. The Air bags are supplying and equal and opposing force in the opposite direction to provide equilibrium with all components. The rear axle, springs, wheels and tires are still supporting the same mass of this trailer, but using air bags to help support this load. Since the springs are flattening out in support of the load that is being placed on them. Springs will collapse when loaded but will supply an equal force in the opposite direction. They are just compressing to support this load and this is why the vehicle will sag.
Make sense to you?
Jim W.

[Jay D]

I would think that some weight would move!!!! I work on a race car and with the car on the scales when ever you turn any of the 4 springs up or down (raise or lower the chassis) you could see on the scale the #'s (weight ) being moved to the opposite side. LF - RR and RF - LR or both rears would move weight to both fronts and same would go for the fronts. Does that make sense to all. Jay

[rhagfo]

I would think that some weight would move!!!! I work on a race car and with the car on the scales when ever you turn any of the 4 springs up or down (raise or lower the chassis) you could see on the scale the #'s (weight ) being moved to the opposite side. LF - RR and RF - LR or both rears would move weight to both fronts and same would go for the fronts. Does that make sense to all. Jay

If you are only changing one corner, then you will move weight as the diagonal wheels act as a pivot point, but if you raise both on either the same end or side you will not likely see any weight movement, unless you raise it several feet.

[Jay D]

No even a turn or two would so

[TDF5G]

To JIM W yes that helps to understand it better. thank you

I think you're right, but if you were to raise the rear of a vehicle past level then I would think that would put some weight on the front wheels (and some to the trailer), not a considerable amount but some weight.

I too thought about race cars a few days ago as JAY D did. Crews make many adjusments to suspension components to move weight around and improve handling, a race car has to weigh a certain amount, but that's another discussion.

After thinking this over and doing some experiments I might not be taking in to consideration the hitch weight of a trailer possibly, I must be thinking about a vehicle with no trailer. I do understand the way a WDH hitch works. It's just the air bag thing I'm still working on.

I'm not really agreeing or disagreeing with anyone here, I'm only trying to understand it. Just because someone states something does not make it true. So I'm doing my own research.

Thanks to all the replies, this is interesting. I'm sorry to get away from the original post here. I don't believe an air bag increases the GVWR or GAWR of any vehicle. I do believe an air bag helps spring rate (compression) but not load capacity. I'm just curious about the weight distribution.

[christopherglenn]

Adding air to airbags in the rear suspension will raise the rear of the truck (duh), and if not towing, thats about it. With a trailer attached in the bed (5er / GN) you get about the same result. With a trailer attached to the bumper / reciever hitch the weight is well behind the axle, and raising the rear axle will do little to nothing to the front axle - unless you have WD attached. Raising the rear with WD attached will unload the wd (as noted on page one, air up and the WD goes slack). A similar effect happens crossing anything that raises the rear axle above (an imaginary line between the front and trailer axles). Think a speedbump, or cresting a hill with either the front or trailer below the other axles. When this happens the front axle unloads (the weight is behind the rear axle, and without working DW it is no longer shifted off the rear axle), as well as shifting back the weight that the WD transfered to the trailer axle. The WD acts like a spring (it is a spring, or two) allowing it to streighten out unloads it.

[TDF5G]

Yes I see what you're saying. I do understand the WDH as I said before.

But now I'm thinking of gravity. If you parked a truck and trailer on a hill, say going down hill, wouldn't there be more weight on the front axle than the rear? And vice versa if going uphill. The rear would be higher that the front. I'm not talking about a tremendous amount of weight but a few pounds would transfer from one axle to the other wouldnt it? Just due to gravity.
I think it would be like two guys lifting a log, the lower end would be heavier.

[happytrails]

I have air bags and I didn't put them on to try and get within my payload that I am very likely exceeding. I keep about 40PSI in them when hauling. In reading about WDH I know/read that some of the tongue weight (which adds to payload) is shifted back to the trailer and from what I read it is around 30-33%. I don't know if that is accurate, it's just what I have read. From what I understand if I have a tongue weight of 1000# then about 300# is transferred back to the trailer thus leaving me with only 700# as payload. If what I have read is wrong please let me know and give me a good source where I can read up on it.

Once I added the air bags I DID have to adjust my WDH. What the air bags did for me, and what I wanted them to do, is take out some of the bounce. I travel a lot of back roads that have a lot of swells and dips and the truck was bouncing A LOT. Someone recommended air bags so I got them and they were right; not nearly as much bounce.

If by some crazy miracle they did actually move some of the tongue weight back to the trailer it probably didn't make a difference because I still have to use a WDH to finish the job. The other part of the WDH for me is SWAY CONTROL!! Even if the air bags could completely do the job of the WDH you still have to have some sway control don't you? My WDH has provided me with fantastic sway control as I have not noticed any sway even when trucks pass me up.

All I can say is my combination works well for me and so far I feel VERY comfortable that I can easily maintain fantastic control of my rig under normal and some stressful driving conditions. Oh and a great feature that I had only read about in my truck manual (until last weekend) that is on my Tundra is that it has it's own sway control and IT WORKS VERY WELL! (real bad road condition) When it went off it sounded like anti-lock brakes which is essentially what it's doing but just applying braking to different wheels to get the back end straight again. Keeps the tail from wagging the dog. Thank you Toyota, you probably saved my truck and trailer from running off the road.

[scrnt]

for those of you that have air bags what on compressor do you use? what size i am looking at the air lift 5000 bags.

[rnkburg]

I had there compressor on a previous vehicle, it didn't last very long. I did like the gauges and controls in the cab though. This round I am not using a mounted compressor just fill/ check when I need to. Plus i ran out of mounting room under hood

Sent from my PC36100 using Tapatalk 2

[happytrails]

I don't have on board compressor. We camp quite a bit so I leave mine at 40 and I use some of those caps you can get at auto parts stores that have different gauge level numbers and will be green if good or red if bad. I just check to make sure they are ok before I leave. One thing I can tell you is that when I was constantly checking my bags I was somehow loosening the needles to a point where they started leaking. It took me a little bit to figure out where the leaks were but now that I know I keep a needle tool in my truck and some spare needles. The gauge caps I bought also keep a good seal on them so they are less likely to leak too.

[Jim W]

I would think that some weight would move!!!! I work on a race car and with the car on the scales when ever you turn any of the 4 springs up or down (raise or lower the chassis) you could see on the scale the #'s (weight ) being moved to the opposite side. LF - RR and RF - LR or both rears would move weight to both fronts and same would go for the fronts. Does that make sense to all. Jay


Jay

With a race car they are designed to support so much weight on each corner (tire and wheel along with the suspension components) correct? Now each corner is supported by a coil spring attached to some component at that corner. When you adjust the spring to collapse it or extend the spring you are changing the load that this spring will support( spring rate) in so doing you are transferring the remaining weight to the other corners to be support.

With air bags these are not collapsing or extending the leaf springs on the truck. Therefore they are not changing the spring rate so the load they support (leaf spring) has not been transferred to another part of the truck. They are just supplementing the added force to carry this load on the leaf springs.
Jim W.

[Jim W]

for those of you that have air bags what on compressor do you use? what size i am looking at the air lift 5000 bags.

I bought the system that Air Lift offers the Air Lift Sure Set system No. 25004. The compressor is mounted on the inside rails of the frame by the transmission. In this way the Air tubing runs are not too long. The kit includes the compressor, tubing, controller with gages, manifold with transducer and all of the wiring for the install.
Jim W.

[christopherglenn]

If you are going to manually fill the bags, any compressor that will hit 80-100 psi will work. The higher the psi rating, the less air it pumps per cycle of the piston. In a pinch you could inflate with a bicycle pump.

I will give you that a SLIGHT ammount of weight can be shifted to the front axle (due to gravity) by lifting the rear. Attach the trailer (no wd) with the airbags empty, put detail tape vertical above the centerline of the rear axle. Inflate the airbags to where you want it, and put a second piece of tape vertical above the rear axle. The wedge between the pieces of tape would be moved from behind the rear axle, to in front of the rear axle. The huge distance between the axles, a few percent of the weight of the wedge actualy shifted from axle to axle. As far as weight shifted on the trailer, same deal, raising the tounge / pin 4 inches - 20 feet in front of the axles - with 10 feet of trailer above the axles, you would shift 2 inches of roof from behind the axles to in front of the axles. Unless there is an AC there, there isn't much weight to move, and 20 feet from the tounge / pin you would see an even smaller percentage change up front.
Once you put WD on the effect from gravity is unimportant, a few lbs shift from gravity VS hundreds of lbs from the springs in the WD.

[rhagfo]

I would think that some weight would move!!!! I work on a race car and with the car on the scales when ever you turn any of the 4 springs up or down (raise or lower the chassis) you could see on the scale the #'s (weight ) being moved to the opposite side. LF - RR and RF - LR or both rears would move weight to both fronts and same would go for the fronts. Does that make sense to all. Jay

If you are only changing one corner, then you will move weight as the diagonal wheels act as a pivot point, but if you raise both on either the same end or side you will not likely see any weight movement, unless you raise it several feet.

Let me clarify the above statement.

1. To all those that believe that lifting the rear will transfer weight to the front, for the discussion here no! I absolute measurement yes, but the amount in the amoutn of lift we are discussing would likely be less than 5# on an 8,000# truck.

2. To the statement of weight jacking a race car 100% true, but only because corner to corner you now have a pivot point involved.

Say you add two turns on a spring on the right rear of a race car the left front will see increased weight, because you have created a pivot between the left rear and right front!

If you lift both rear corners the same the pivot point is now between the two front wheels, so there is no weight added to the front axle, we are talking inches not feet here.
Now if you lifted the rear of the truck say three feet, then weight would start to show up on the front axle.