Air Bags - What Do They Do?

[mrxlh]

Originally Posted by Festus2

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]

Originally Posted by mrxlh

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.


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)

Originally Posted by mrxlh

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]

Originally Posted by mrxlh

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.

Originally Posted by mrxlh

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.

Originally Posted by mrxlh

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.

Originally Posted by mrxlh

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]

Originally Posted by JRTJH

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!

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]

Originally Posted by 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.

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]

Originally Posted by rhagfo

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.

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.