Rear "Helper" Airbags for pulling trailer- Issues and possible fix.

WhiteH2O

Observer
I drive a 2006 Lexus GX470. I just got back from Utah where my set-up was Iron Man springs and struts with Air Lift bags in the springs hooked up to my stock air system (stock GX has rear airbags with height sensors). It was set to give me about a 1/2" lift from stock with no load, and hold the height with the Turtleback Trailer attached.
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I was climbing a steep hill (the hill between the 4 way (by Sunset Pass) and the Flint Switchbacks in the Maze), so outside pressure was being reduced and therefore the pressure in the bag was probably increasing. I thought the stock system would be able to monitor and adjust accordingly, but BOOM!!! It took my wife and I a while of sheer panic that I blew something more important, but no fluids leaking, no flat tires... Must be the rear airbags? Yep, whew!
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Anyways, I need to rethink the system. It was a great idea in theory, but was a little lacking in practice.
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I'm thinking of putting in the Coil-Rite airbags and just simply connecting them to an air valve so I can manually adjust them and scrap the stock compressor system. I always carry my compressor for airing back up, so I could adjust them, but I'm assuming I would have to adjust them a lot when on trips where I change altitude a lot (like in Canyonlands, Washington Mountains, Montana- so nearly all of my trips). Should be fairly set and forget for trips around home, I think.
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So what are other people doing to control their air bags? Has anyone tried to do a manual system like I'm thinking about? If so, how much of a pain is adjusting them to changing altitude? Any other options I'm not thinking of?
 

Martyn

Supporting Sponsor, Overland Certified OC0018
We set up manual systems with all of our airbags. The height sensors don't work well off road due to constant terrain changes. Set up each air bag with it's own air line and filler valve. Fill the bags based on the height you require not by pressure. A small on board compressor, or 12 volt plug in will do the trick as the volume of air is low.
 

WhiteH2O

Observer
Thanks Martyn, its good to get input from a good source such as yourself. This is how I will set it up from now on.

Do you ever have any issues with elevation/pressure changes? Like do I have to carefully monitor ride height, or should it be more set and forget?
 

1stDeuce

Explorer
Most likely it wasn't the pressure increase that blew them. (It's not that significant, even going from sea level to 10,000 only changes pressure by 4psi...)

With lift springs, it's likely you just need a taller set of bags. The bag is supposed to support the weight mostly on it's ends, and just be contained by the coil spring. The material they use doesn't really stretch much, so if your bags are too short, you'll need to run a LOT more pressure to get any height increase out of them.

I was using bags with 1" taller coils in my TJ, and instead of cutting the jounce bumpers down some like the instructions said to do, I left them stock, so the bags could push up at the ends. The other thing that happened to my setup was that occasionally as the suspension moved, the house would pull off the barb on the bag, or the barb would pull right out of the bag! Psssshhhhhhhhttttt!! It sounded just like a speared tire and scared me a couple of times. :)

Any idea how much pressure you were running to get 1/2" of lift out of them? It should have been ~15-20 based on what I saw with my Jeep. If you blew one due to high pressure, it's a sure bet the bag was too short. You might look into the bags for a Tahoe, which were similar in dia, but a couple inches taller.

I do like the idea of having the factory system run the air... What does it do if you cross up the truck and stop though? It might just need a pressure limiter so it can't get past ~50psi or so... You should not need more than 50psi...

Good Luck!
 

kojackJKU

Autism Family Travellers!
1stduce. He had them hooked to the lexus air compressor, and it just kept pumping. They are not made as replacements for the stock lexus bags. I think it was the air pressure (not ambient), that blew them out.
 

WhiteH2O

Observer
Thanks 1stduce, that was helpful. They were shorter than I thought they should be, and I had large hockey-puck type spacers in there to try to fill up the gap, but I bet you are right about them being too short still. I'm thinking I should go measure the gap in the spring and find the right sized airbag for the space. I'll look into the Tahoe bags, that seems like a good bet. I never actually thought about 0'-10,000' being only 4psi, but that is an excellent point. I liked the idea of the stock system running them also, but there are known issues with the sensors and the entire system really. I think I'm better off just going full manual like how Martyn runs his.
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I had this system in for a few months prior to this trip, and while I think that, especially with the knowledge of how little ambient changes with elevation gain, it was the set-up of the bag that blew them, I don't think the stock compressor just kept running (the sensors were set to the height I wanted and they were tested multiple times). Others have had the same set-up with better success, although I don't believe many have kept that set-up long-term. The stock system should cut off the compressor when the sensors see that the rear is at the right height. I think possibly that I as climbing a large hill, putting extra weight back onto the rear shocks could have also had something to do with it. I don't know what pressure I was running, but when it pumped the bags up from deflated, it didn't seem like much (it was quick and the pump is tiny). I would guess under 20psi for sure without the trailer to get the 1/2", but it sounded like a lot of air when it blew.
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Either way, I think having the correct sized bags set-up to a fully manual system is the correct long-term solution here. Thanks everyone for the input.
 

Martyn

Supporting Sponsor, Overland Certified OC0018
As a guide line helper after market helper bags that fit inside coils should be 1" shorter than the length of the coil in it's normal position and close to the internal diameter as the inside of the coil.
 

1stDeuce

Explorer
Yeah, I got that you were using the factory setup, and I like that. If it does occasionally wig out, you could always just put an air pressure relief valve in the plumbing so it cant' over-pressure the bag... Hopefully a very situation specific instance of it trying to correct for a terrain isssue... Does it control both bags together, or independently? Ie what does it do if you cross up the rear? I would assume it just averages the suspension heights and more or less does nothing... If it pressures them independently, and starts pressuring the "stuffed" side, and bleeding off the drooped side, it's garbage anyway, and you should just go manual.

Good luck with the longer bags!
Chris
 

kojackJKU

Autism Family Travellers!
I would just set it up manual anyways. Its easy to adjust then, You don't have to worry about HOW it's workin. A set it and forget it kinda deal. Mine work great this way.
 

Triplesnake

Adventurer
When I installed Air Lift bags on my R51 Pathfinder, I set them up with manual, individual valves for each bag. They have been very low maintenance like that, but I've only had to adjust them a few times to tow our trailer locally. Adjustments are easy since they are low pressure and volume. I routed the two valves to the back of the truck near the trailer hitch and just use a manual bike pump and a digital pressure gauge.
 

1stDeuce

Explorer
Wow, I just found the sticker for the bags I put in my TJ... they have a max pressure of 35psi, and a min of 5psi. I believe the stock lexus air system runs air shocks, not bags, and is therefore likely capable of at least 100psi. If so, it would easily be capable of blowing one of these low pressure bags... kojackJKU's suggestion to just set it up manually is probably the best plan at this point. You could add a small tank and turn the factory compressor into on-board air to fill them with, and even add the gauge and up/down switch to make them controllable from the driver's seat.

If you four wheel much, I'd also recommend connecting them together on one fitting. That will allow air to transfer between the bags, and won't limit articulation as much. Plumbing them individually is much better for stability though, so if stable towing is the concern, then having separate fill lines is indeed better.
 

kojackJKU

Autism Family Travellers!
In a coil spring, they don't limit articulation much. My tires will limit articulation before the air bags come into play.
 

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