Adding Airbags to AHC (1 Viewer)

[TeCKis300]

Picture is probably too subtle to show but it's part of the why - adding airbags creates the ability to level the vehicle side to side and front to back for backcountry car camping. In the pic, I have the right side jacked up 2" with about 25 PSI in the right rear bag. Secondly, while AHC has been tremendously robust putting up with a sensor lift and 2000lbs payload, it couldn't hurt augment the system. I had Airlift airbags sitting in my garage meant for my previous LX470 that I never installed, so figured I'd give it a try with nothing to lose.

For more context on numbers, I tow a heavy trailer (8000lbs, 1200lbs tongue). The LX is rated at 1385 lbs payload and I'm way beyond that with scales showing 2000lbs payload and 1700lbs on the rear axle alone. AHC has been great over the thousands of miles I've towed without complaint, while tailoring just the right spring rate and damping at all times, without sacrificing clearance or sagging as it's constant height regardless of load (to a point). Not unexpectedly, at those weights and particularly when the trailer tongue is down grade, I cannot get into high mode as the system probably detects over threshold AHC pressures, which this airbag mod may be able to remedy.

The system now has 3 forms of payload support. Stock AHC uses tender coil springs paired with hydraulic shocks. Adding airbags creates a tailorable 3rd load support systems. The goal is to transparently relieve some load from the hydraulic system. Without interfering in its ability to maintain great ride quality on road, or hampering articulation off-road.

I only just threw it in and haven't driven much yet, but I'll report back whether I've met these goals.

 

[TeCKis300]

As I installed this more as an experiment, I wanted to minimize mods that were done to the vehicle. The airbags I'm using is Air Lift 60728, meant for the 100-series. I believe they are shorter in free length than what is normally spec'd for the 200-series. Diameter fits correctly in the coil. Shorter works to my advantage IMO.

I didn't cut the stock jounce limiter aggressively, and only took one segment off (of 4). Fully installed, this shorter bag still has 1/2" free length clearance as full droop per the installation guide.

Here's the stack up. Note I also have a 30mm spacer at the top to augment AHC for weight and sensor lift, so I'm not reliant on the airbags at all. They are supplementary which is the way I want them as airbags can have limitations for full articulation, both in compression and extension.

Here's where I ran the airlines. There's a convenient bracket for the tailgate torsion bar (LX only) that already has to available holes. I believe this bracket also exists for the LC? Bent the bracket down a bit to have a better angle to fill. And enlarge the hole just a tad with a stepped bit and the Schrader valves fit nicely.

 

[grinchy]

If nothing else you’ll be able to regain effective spring rate for factory coils and augment to your new post mod base payload. I’d be interested in what constant non towing psi you choose to run, as well as feedback on if 0 psi vs say 3 psi makes a difference to comfort or ride compliance when not towing.

 

[Moby]

Helper bags are great, thinking of this for my 200 as well. I ran rear air over leaf bags on my FJ-62 so that I could pull a leaf out of the OME pack for unloaded comfort and maintain support when loaded just like you. Was working on automated leveling with my CarPC and Phidgets board (for the sensors and valves) when the truck was destroyed. Now you can just buy auto levelings systems. But they are way more money than they should be in a complete kit.

 

[TeCKis300]

Posted install notes to the second post.

 

[rmtannerjr]

We tow very similar loads and after my camper purchase I knew my AHC needed help. My daily truck weight is just at 8000lbs but haven’t weighed with the trailer as I don’t think I want to know.

I have 270k miles on my 2011 LX with no AHC service as of yet. I went with an Airbag Man setup from Australia as even Slee didn’t have a suggestion.

I have a Black Series HQ17 off-road camper. About identical weight loaded that you have. And with the Slee rear tire carrier, 24gal aux tank, full drawers, and high lift, even the Airbags and a nice Blue Ox WDH aren’t doing the trick.

My only ideas now are to swap for LC springs if possible, or shed some weight by relocating the tire and jack to the back of the camper when needed. (That camper has two spares that are hardly both needed in the states anyway)

Let us know how it works out with a load as I may just need to finally do an AHC fluid change. Preventative maintenance has usually been a waste of time and money on these rigs for me.

 

[grinchy]

I may just need to finally do an AHC fluid change

Yes, it’s past time.

 

[TeCKis300]

Leveling working out great to get that last fine adjustment. Slammed AHC in low for ease of access and aired up the right rear to about 40psi for about 2". The flexibility of the suspension is awesome, and it's always worth the extra bit of effort to level out the car for sleeping comfort. In contrast, friends were stacking RV legos and rocks, and of course giving me a good ribbing about the robot car that just dropped itself 4" and is level with a quickness. Lucky for them I had dinner responsibilities that night, and with a gang of hungry kids, I got to cooking while they continued setting up before sundown.

We tow very similar loads and after my camper purchase I knew my AHC needed help. My daily truck weight is just at 8000lbs but haven’t weighed with the trailer as I don’t think I want to know.

I have 270k miles on my 2011 LX with no AHC service as of yet. I went with an Airbag Man setup from Australia as even Slee didn’t have a suggestion.

I have a Black Series HQ17 off-road camper. About identical weight loaded that you have. And with the Slee rear tire carrier, 24gal aux tank, full drawers, and high lift, even the Airbags and a nice Blue Ox WDH aren’t doing the trick.

My only ideas now are to swap for LC springs if possible, or shed some weight by relocating the tire and jack to the back of the camper when needed. (That camper has two spares that are hardly both needed in the states anyway)View attachment 2603702

Let us know how it works out with a load as I may just need to finally do an AHC fluid change. Preventative maintenance has usually been a waste of time and money on these rigs for me.

I've yet to run it with my trailer but I've got few thousand mile trip coming up this mth. Thanks for sharing your incredible rig. Pretty shocking weights and I scale my LX in at 8000lbs while towing. You're at 8000lbs before hitching up! Incredible that anything stock will tolerate that kind of load, and it speaks volumes to how incredible AHC is to even hang in there. 270k miles no less!

I think you've got the right setup there for airbags. Could combine them with front and rear spacers to preload the coil springs and help AHC a bit. I do agree you may be heavy enough to warrant normal LC springs. Let us know how it all works out.

 

[tbisaacs]

We tow very similar loads and after my camper purchase I knew my AHC needed help. My daily truck weight is just at 8000lbs but haven’t weighed with the trailer as I don’t think I want to know.

I have 270k miles on my 2011 LX with no AHC service as of yet. I went with an Airbag Man setup from Australia as even Slee didn’t have a suggestion.

I have a Black Series HQ17 off-road camper. About identical weight loaded that you have. And with the Slee rear tire carrier, 24gal aux tank, full drawers, and high lift, even the Airbags and a nice Blue Ox WDH aren’t doing the trick.

My only ideas now are to swap for LC springs if possible, or shed some weight by relocating the tire and jack to the back of the camper when needed. (That camper has two spares that are hardly both needed in the states anyway)View attachment 2603702

Let us know how it works out with a load as I may just need to finally do an AHC fluid change. Preventative maintenance has usually been a waste of time and money on these rigs for me.

Would love to see more of this truck!

 

[rmtannerjr]

Well to be honest, I wish I were more forum involved. Love this place, but like most of y’all I’ve got a long list of hobbies and a couple of young kids that demand my time.
Tbisaacs, I know you’ve ask before and sorry I haven’t delivered.

The spacers are a good idea, my brother has a new heritage LC I’m hoping he will upgrade the suspension soon giving me his springs.

Back on topic of AHC, the bags really actually help in my day to day driving, and I really am not sure how I’m any heavier than the rest of the rigs fully outfitted. Need to get some true axle weights but we take it easy. I imagine if I throw the heavy Tepui back up on the rack, the bags would be a huge help at camp like you said.

The WDH made all the difference in highway stability and did allow for “Normal” height but you go off road and if forced to remove them, it struggles to stay in Normal even with the bags (30lb max for some reason).

I added insult to injury when upgrading my propane to dual 40lb tanks up front on the camper.

I don’t mean to hijack so these pics are to show the bags are keeping it in normal. Couldn’t hit “High” and I could have used it as you can see.
Our first real Moab/Colorado camping trip was pretty awesome from Louisiana last Fall. If only Texas wasn’t so damn big we’d go more often!

 

[TeCKis300]

About 800 miles in, fully laden with the camper, and airbags set at 10 PSI in normal position.

Impressions are this is pretty awesome. Not much perceptible difference in terms of control, ride comfort, or stiffness, as AHC has always adapted for these concerns nicely. AHC in itself is likely a progressive spring rate as it does seem to adapt to even 2000lb payload with solid support and control. I can only really tell the airbags are in play as I can't as readily get into L with them inflated and no trailer on. Yet I can comfortably get into H when necessary even with the trailer on.

I've come across some pretty gnarly tertiary roads where it can't make up if it wants to be flat, rolling humps, or side to side camber changes at all sorts of intervals. AHC has always done well handling and damping these oddball roads even at higher freeway speeds. Was worried airbags may change how the system dampens these conditions but the control is still compliant and tight. Another quality I admire is the systems ability to seemingly never bottom out on g-outs, something you'd think would be a common occurrence hucking 2,000lbs on the rear axle. Even as good as stock was, it's perhaps here that the bags did help tighten things up a tad, without impacting ride quality.

The adjustability of the bags is great as I can air them down once unhitched and maximize articulation for off-road exploration. Throw AHC in L, and let the air out.

 

[1world1love]

I really need to get weighed. I can’t believe you guys are pushing 8k. I joke about it but I have never thought that I was that high when fully loaded. I guess you guys have a 24 gallon LRA which is going to add a good 170 lbs, but still.

With front and rear bumpers, swingouts, roof rack, drawers, a family of four, and all our s**t loaded in the back and in a roof box, and 20L of water and 4 gallon rotopax, and my AHC doesn’t sneeze. I do think it is time for some spring spacers though.

 

[Bomar]

With airbags and towing does your truck still lower at 60+mph (whatever the speed is)?

Is it less disruptive during the drop if it happens?

 

[TeCKis300]

With airbags and towing does your truck still lower at 60+mph (whatever the speed is)?

Is it less disruptive during the drop if it happens?

Must have missed this. Lowering at freeway speeds works as normal, without any noticeable difference.

The only things I have observed with too much spring rate in the rear (i.e. pressure in airbags), is that the rear will take much longer to get into low (if at all) with no load. Which makes sense as AHC is attempting to dump all pressure to get the rear down with something else holding things up. A follow-on side effect is that it takes much longer to get to Normal height. I suspect it's due to the AHC dumping all pressure and volume and fully relaxing the suspension spheres, including the 5th accumulator. So when trying to return to Normal, it doesn't have the benefit of pressurized fluid in any of the spheres, including the 5th accumulator. I've also noticed AHC will dump more fluid into the fluid reservoir to the extent it may actually spit out the reservoir vent.

Solution is not to use excessive air pressure in airbags. Or too much spring rate with aftermarket springs (for a given load).

For my setup, I use only 10-18psi in the bags.

 

[Bomar]

Thank you for the answer.

I don't think currently I need airbags but will look into in in future.

 

[radman]

@TeCKis300, do you think it would be possible to get the bags in with full droop (and not removing the springs)?

 

[TeCKis300]

@TeCKis300, do you think it would be possible to get the bags in with full droop (and not removing the springs)?

Yeah, I actually think that's possible. Will need to cut the bump stop and route the airline but if you can manage that with the spring in, it's very possible to squeeze the airbag in.

 

[radman]

Stupid airbag question if the day:
Does the airbag affect the spring rate by expanding horizontally into the spring, or does it actually provide vertical lift? Or both?

 

[TeCKis300]

Stupid airbag question if the day:
Does the airbag affect the spring rate by expanding horizontally into the spring, or does it actually provide vertical lift? Or both?

The horizontal expansion probably doesn't provide appreciable spring rate. As expanding the spring diameter actually tends to reduce rate, yet the minor engagement by the coils on the bag sidewalls might tend to increase rate minimally... about a wash. Most of the increased rate will be provided by the ends. With coils constraining airbag volume upon compression, increasing the progressive rate.

 

[radman]

The airbags I'm using is Air Lift 60728

Air Lift 60728 vs Airbag Man CR5081HP vs Airbag Man CR5114HP

My understanding is that the Airbag Mans are just rebranded firestone bags with additional sleeves, and the 5081 and the 5114 both specify AHC (100 series vs the 200 series) - with the difference being slightly different heights.

It seemed like the Aussies were being very particular about that height difference, and wanted measurements before recommending one over the other.

My stupid airbag question of the day: does the height really matter for our use case? wouldn't all those bags eventually get to the same height (albeit with different psi)?