Air bags for load management

[njtaco]

I have to say I still don't get why this would be a significant effect.

...SNIP...

What I will concede is that too much tongue weight will make the front end and steering lighter than it should be, and that airbags won't cure that problem in the slightest. But I can't see them making it worse.

Michael,

Many of my experiences are with tongue weights in excess of 800 lbs at times, with and without weight distribution gear, so perhaps my analogy is skewed to my conditions. I agree that air bags are not THE solution either, which is why I suggested shocks in my earlier post. I should not have typed "unloads the front of the truck" as an absolute, as every situation is different.

I think we agree on the physics of this, I just presented it wrong. Another difference is you remember the math behind it...I've forgotten too much from HS and college

Bob

 

[michaelgroves]

I think we agree on the physics of this, I just presented it wrong.

Quite - i think the part we agree on is that air bags are a bad idea if they're intended as a way of dealing with excessive tongue weight. I was just clarifying that I was also agreeing with Dave - other things being equal, the problem shouldn't be significantly worse with airbags either!

Actually, I think the only good solution to high trailer tongue weight is to move it - either redistribute the trailer weight over its own axle/s, or have the towing ball closer to the towing vehicle's rear axle. (I suppose fitting a really heavy winch on the front bumper might help also! )

 

[xcmountain80]

Physics or not my front (different than what is being asked about) doesn't unload in the front when the bags are inflated. It really helps in the sense of ride quality. GIven that this is a pickup with leaf springs I'd say get a custom leaf pack from deaver springs and be done with it. Forget the bags just go with the springs. I know those trailers aren't to evil in weight you could also look at a product called super springs which I use on my wife's explorer. They are an additional spring that bolts to your existing set and helps even out the load.

Aaron

 

[Hilux_Max]

Guys,

I need some real world experience in relation to airbags here.....I have 2 inch raised/reset factory leaves on the back of my hilux and a 1 inch block below them for that little bit more height. When empty, the hilux is great and I good very good rear flex when offroading, but the downside is when Im loaded up with camping gear the rear of the hilux sags abit too low for my liking. i dont want to get heavy duty springs at this point in time so I bought a pair of good quality airbags for the rear to suit the height increase, and aid with the increased load when camping.

Now heres my dilema....

My neighbour who has a suspension business and who did my suspension setup says that if I fit the air bags to the rear, that when my rear suspension is flexing that I'll tear them.You know, when they are fully extended?

Could somebody explain to me the possibility of this happening? Especially when the hilux is empty? I have had them for ages and am too scared to fit them and I cant get a decent 2nd or 3rd opinion from anywhere.

My other option is to sell them and fit an add-a-leaf for added capacity. I dont want to get a complete heavy duty 8leaf pack or something like that because tis my daily driver aswell and dont want an unladen rear with such stiff springs.

thanks guys

 

[Tucson T4R]

I run inner coil air bags on the rear of my 4Runner. It has worked out great for me. Unloaded I keep them arounf 5lbs, when packed up for camping with the 2000 lb Kimg Kamper hooked up, I run the bags at 15-20 lbs.

I have the air line plumbed to tie thebags together, that way when flexing slowly off road the compressed bag can shift some air preasure over to the bag being extended. This only aplies to slow flex situations and doesn't shift air fast enough to effect higher speed flexing.

Bottom line, I've been usiung them now a couple years and love the set up. No problems.

 

[Dave]

Hilux_Max, would limiting straps be an option if the droop in your suspension exceeds the limitations of the bags?

 

[spencyg]

Now heres my dilema....

My neighbour who has a suspension business and who did my suspension setup says that if I fit the air bags to the rear, that when my rear suspension is flexing that I'll tear them.You know, when they are fully extended?

A good question....one that I also have. I just installed my bags yesterday and while I was taking it for a test drive I was wondering what happened if the axle tops out and stretches the bag. The bags are securely bolted top and bottom, so there is no place for stretching. The material seems extremely rigid which makes me think it won't "stretch" well. I think the only thing to do is run it and see what happens. At the end of the day, they supplement an existing system, so if by chance they fail, it isn't the end of the world. I can certainly see some upcoming carnage if the axle drops away, but it may not be an issue. I'll be sure to report if/when something happens...

Spence

 

[ntsqd]

In extreme articulation an air spring mounted outside of the leaf springs will see slightly more extension than the spring itself. Inboard mounted air springs will see less extension than the spring.

Roger Brown's technique for "driveway articulation ramp" should work well for this investigation, so long as your ramps are suitably rated for the vehicle's mass. Recommend that one end of each rear damper be removed so that they do not act as an artificial limiter.
http://4crawler.com/4x4/CheapTricks/Ramp.shtml

By doing this on a piece of flat ground you can work up to the vehicle's maximum articulation. With care in how you block up the ramps this can result in it being safe to crawl under the vehicle. Then you can place the bags in the expected location and see if there is a problem or not.

 

[madizell]

If you have enough load in the bed to drop the rear 2 inches, even if some part of that is the tongue weight of the trailer, I would not think it excessive and would not expect to find controlling the load a problem with standard suspension, which makes me wonder just what you are experiencing. If the bobbing is up and down versus side to side, I would have to ask if the bobbing is road induced, or if it bobs around even on relatively smooth flat ground.

Side to side shifting is usually tongue weight imbalance, and you would need more tongue weight. The same condition can also contribute to up and down bobbing, but the shift is more circular than linear. Usually if you have something between 250 and 500 pounds of tongue weight, you have plenty, depending on how much the trailer weighs altogether. If you have a 1,500 pound trailer and the tongue is light enough for you to lift bodily (and easily), it is probably too light. If the tongue weight takes your truck straight toward the road, it is probably too heavy for the vehicle as built.

If this is just a case of once you hit a bump it just keeps on bouncing, you need more damper. Change to adjustable shocks or another shock with more damping.

However, since you are only dropping the suspension by 2 inches fully loaded, I think heavier springs or air bags are not the answer. It sounds to me as if you are carrying the load, just not controlling it. Try loading the truck without the trailer attached, then attach the trailer and see how much of that drop is attributable to load and how much to the trailer. If the trailer makes a good part of the difference in compression, I would look at an equalizer hitch, which will bring your trailer load back toward level and help support the weight of the tongue. That alone should take care of the bobbing all other things equal, but if it doesn't, trade up your shocks.

 

[Ron B]

Hilux_Max, would limiting straps be an option if the droop in your suspension exceeds the limitations of the bags?

I second this -- I had to do it in my truck when I went to a bag suspension (a little different application being independent suspension, but same problem).

 

[michaelgroves]

I have the air line plumbed to tie thebags together, that way when flexing slowly off road the compressed bag can shift some air preasure over to the bag being extended. This only aplies to slow flex situations and doesn't shift air fast enough to effect higher speed flexing.

I did the same thing as an experiment, and didn't like it at all! Although part of my rationale for fitting airbags inside the rear coils was that I could pump them up when on the road, and get rid of the anti-roll bar altogether.

This worked absolutely fantastically (full articulation when the bags were deflated, much less body roll when inflated), but when I interconnected the bags, the body roll became worse than ever, especially on a slow, sustained corner. (I guess the air had time to move from one bag to the other).

Off road too, it didn't seem to offer any net advantage - the benefit of one wheel being forced downwards when the other is pushed upwards is offset by the fact that the inflated bags reduce overall axle movement.

 

[madizell]

I can't imagine a situation where having the bags tied together would actually be a benefit. Off road, it could only be a detriment. At most, if you build an inter-tie, at least install some kind of solenoid to you can open and close the link, and I would leave it closed most of the time, especially in irregular terrain.

 

[michaelgroves]

I think the idea is that, on severe undulations where the vehicle would get cross-axled, as one wheel takes the weight and gets forced upwards into the wheel arch, the air gets pushed into the opposite airbag, and pushes that wheel firmly down onto the gound.

 

[ntsqd]

I think the idea is that, on severe undulations where the vehicle would get cross-axled, as one wheel takes the weight and gets forced upwards into the wheel arch, the air gets pushed into the opposite airbag, and pushes that wheel firmly down onto the gound.

Some of the Toyota IFS crawler guys have taken to using air shocks (the old fashioned kind, not those used on current comp rock buggies) plumbed together to create a forced articulation system. Those that have done it swear by it for crawling.

Except in certain circumstances I can see it not being terribly desirable for Overlanding.

 

[xcmountain80]

I second this -- I had to do it in my truck when I went to a bag suspension (a little different application being independent suspension, but same problem).

Yeah thats what I need I keep breaking the nipples on the bags from to much flex. I have limits up front in order not to pull the cv's out.

Aaron