Pros & cons of air suspension.

[G-force]

I am planning to build me a trailer, for family RR. I see a few of you have swapped over to air suspension, and this makes me curious. Problems with ride hight vs. load is then adjusteble, but is the trailer smoother along both highway and dirt roads??

I am also taking in to consideration to have independant suspension with the air suspension. Is this the best way to go? Of course, shock absorbers are included in my plans for this trailer.

I am aiming for about 1000-1200 kg fully loaded, and something up close to 4 meters of total lenght. Total hight i transport is close to 165 cm.

The project is based on a Norwegian military trailer, wich was used to transport 960 liters of water in an aluminium tank. The tank is to be removed, and some small changes done to the frame, to fit 33" BF AT on original G-wagon alloys.

Should turn out pretty sweet:sombrero:

Thanks u guys.

 

[Martyn]

Two of the pros as you mentioned are ride height and load adjustability, plus speed of reaction to changes in terrain.

As we know from physics all actions have reactions, so a quick moving suspension in one direction will move as quickly back in the other direction, so good shock as essential, along with bump stops and limiting straps to control the amount of movement the suspension has.

Around 4.5" or 114 mm of travel is more than adequate for most off road situations.

On the negative side, it's just the small things. Micro leaks in the air system is the most common, resulting in loss of air bag height over a few days or a week. As they are low volume systems a loss of a little air shows up. By their very nature it is not a sealed system and it requires periodic inspection and adjustment.

Better add a small compressor to the list.

Not as efficient as the air bag system, is the coil over. The spring ratings have to be calculated based on maximum load, and they need to be pre tensioned, but they have very low maintenance and don't spring air leaks.

If you go with a coil over I'd recommend one with a remote reservoir to aid in cooling. Also have them custom valved for your needs.

 

[G-force]

Both compressor and a small air tank, is integrated in the trailer. Compressed air is so useful in many situasions.:sombrero:

As of leaks, as you mention, i did not know. Is it so, that the air pressure is constant between the air tank, and the air bag? If so, is it possible to integrate an pressure gauge for each of the air bags? This to easyli read out the pressure in each bag.
Or should it always be the same pressure i both bags, regardless of load on the separate sides?
Thanks for the tips. I`d forgot about the limiting straps.

 

[indiedog]

Are each of the airbags independent from eachother? I can see some sense in having them sharing their air so that when one side hits a bump and compresses that air is pushed into the other bag expanding it and keeping movement in the trailer more vertical. You'd have to make sure your load is centrally placed between the wheels maybe as a greater load on one side would push the other side up. Maybe the limiting straps would fix this?

 

[UK4X4]

My small input having built a home made airbag system.

Leaks...I used 316L stainless steel lines with swagelock valves and unions.

I don't have leaks.....mind you they are not cheap if you have to buy them.

10,000 psi rated gear was a bit of overkill:coffeedrink:

My system has one air feed and three isolating valves, so bags can be linked for equal filling then seperated for use.

Shocks- I used some left over landrover bilstien gas shocks- I have found that even fully loaded the trailer suspension is way too active.

I think standard oil shocks rather than gas loaded ones will tame the suspension better, ie the weight of my trailer fully loaded is way less than the rear of a disco 2

Independant suspension - bump steer, my trailer is always shimying around after corners and road bumps at speed.

It does not effect the truck, I can't even feel it, but I can see it in the rear view mirror

Maybe again due to the trailer weight V's shock absorber issue, giving too much movement.

Build time.....standard leaf springs and shocks 1 day

independant arms and air bags....4 day's minimum.

Enjoyment in creating something technically interesting and challenging made up for my time.

Cost 3X the cost of standard springs.

Off road / gravel tracks, the suspensions eats up the bumps brilliantly,
no instant scambled eggs for me.

Changes now after using the trailer for 6 months....change out the shocks for
some sticky oil shocks to increase the damping.

Build is here

http://expeditionportal.com/forum/showthread.php?t=12092&highlight=consolidated

 

[gabepari]

I don't think the air lines are the cause of most leaks. In my experience the air bags leak, just like tires and tubes leak. The rubber is porous, so eventually they will leak down. Not a "con" as far as I'm concerned, as I check my air pressures in the tires regularly since they leak down too.

Gabe

 

[Michael]

I am planning to build me a trailer, for family RR. I see a few of you have swapped over to air suspension, and this makes me curious. Problems with ride hight vs. load is then adjusteble, but is the trailer smoother along both highway and dirt roads??
<snip>

I have a set of Firestone Ride Rite air bags on my 2006 Tacoma. They do a great job of smoothing out the bumps (I also have springs and shocks). I've had no problems at all with leaks. I usually just check them before major trips and typically have to add only a pound or two of pressure. I don't have an elaborate pump system, I just carry a cheapo racing-type bicycle pump, the kind that clips to the bike's frame. A couple of strokes with the pump is usually enough to get them topped off to the 14 psi (ymmv) I normally keep in the bags. From flat to full is only about a dozen strokes, so there isn't a lot of pumping involved at any time. I have them installed with separate valves, so I can balance a load if necessary. The valves are installed on my rear bumper in an easy-to-reach spot. If the bags are all you have installed, they would probably be quite bouncy when carrying the load, so I'm guessing shocks would be a necessity on a trailer. The overall ride on my truck is very solid when I'm fully loaded and I've pump the bags up to maintain rear bumper height.

If you're thinking that having bags plus springs seem like overkill, you should know that the stock springs on the 06+ Tacomas are worthless.

 

[G-force]

Thanks guys, this is great info.

So as i undestand, one of the issues is good oil shock for the trailer. And if i spend the money, i can at least have fewer leaks in the system.
OK, the air ride set up is more expensive than a regular set up with springs, but only marginal here in norway. This is then if you anyway have to buy all the parts.
Though, coil springs are way easier to find in the junkyard, than air bags:bike_rider:
Independant suspension, i want it!! Looks way cool, and takes the bumps better, as i understand.
UK4X4: I like your set up with the different valves. Need to look into this issue, to see how i want this to work.
indiedog: I like this for of thinking, but is this how it works, if the bags "share" the air??
Anyone?

Again, thanks for your input.

 

[UK4X4]

Air leaks...Martyn mentioned days to weeks....mines in the order of months....

Shocks, this is just my idea of whats up with mine..not gospal..Pretty sure Martyn will pipe back up with his input, being the residant expert.

Mine was a garage rumage rather than a designed spring - shock match....

Linking air across the springs, unless you have large air lines the speed at which it transfers from one too another is too slow.

ie standard air bags have a 3/8" npt thread ID of that fitting is in the realms of 6mm.

Yes you can order bags with larger holes, but I was looking for long travel small OD

 

[G-force]

Regarding the oil shocks. I was thinking of using those, because i did not want any "lift" as from the gas shocks. They tend, as far as i have experiensed, to want to stay in the "out" position.
The only thing i want the shock absorber to do, is to limit the movement-speed of the swingarm, so there is no sudden change of ride hight, or swingarm travel.
Maybe do two or three different top mount brackets, so its possible to chose diferent angles on the shock. More vertical, stiffer dampning, and more horisontal, lesser dampning. This to find the best angle at the right load, and then remove the two brackets that are not in use.

This is then tested with water in the 960 liter tank, then filled so the total weight is close to the weight the finished trailer.

 

[Arya Ebrahimi]

Has anyone explored the concept of using leaf springs that are rated nearer to the trailer's empty capacity and then used air-shocks that are used to supplement vehicle suspensions to take up the difference when adding load?

Seems like it would give you the simplicty of leaf springs with the benefits of airbags.

 

[#686 Sahara]

Here's a few photos of what I've done to mine so far. Even with shocks I still get it swaying a little side to side, so I'm in the process of having a swaybar put in to see if that will help. Other than that that you cant beat the ride off road plus since my tent is on top I can adjust each side to level out. And the great thing about independent is the clearance underneath.

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[Martyn]

Both compressor and a small air tank, is integrated in the trailer. Compressed air is so useful in many situasions.:sombrero:

As of leaks, as you mention, i did not know. Is it so, that the air pressure is constant between the air tank, and the air bag? If so, is it possible to integrate an pressure gauge for each of the air bags? This to easyli read out the pressure in each bag.
Or should it always be the same pressure i both bags, regardless of load on the separate sides?
Thanks for the tips. I`d forgot about the limiting straps.

Pressure is not a good way to inflate the air bags due to differences in loading side to side. It has to be done by height.

 

[Martyn]

Are each of the airbags independent from eachother? I can see some sense in having them sharing their air so that when one side hits a bump and compresses that air is pushed into the other bag expanding it and keeping movement in the trailer more vertical. You'd have to make sure your load is centrally placed between the wheels maybe as a greater load on one side would push the other side up. Maybe the limiting straps would fix this?

Bags have to be separate, if they are linked you get delayed compensation and unpredictable movement side to side.

 

[Martyn]

Air leaks...Martyn mentioned days to weeks....mines in the order of months....

Shocks, this is just my idea of whats up with mine..not gospal..Pretty sure Martyn will pipe back up with his input, being the residant expert.

Mine was a garage rumage rather than a designed spring - shock match....

Linking air across the springs, unless you have large air lines the speed at which it transfers from one too another is too slow.

ie standard air bags have a 3/8" npt thread ID of that fitting is in the realms of 6mm.

Yes you can order bags with larger holes, but I was looking for long travel small OD

The stand alone air bags don't leak very much. Issues are with the connectors and the airline.