Rear Airsprings (replace coils with full airbags)

[Jetboy]

Hmmm - Funny how things change over time:

When Land Rover started putting air suspension in their trucks all of the off-roaders started modifying them back to springs - - -

Probably a good idea. Especially if you rely on lucas electronics for keeping them inflated.

I'm kinda skeptical about this myself. I've decided to wait and order the correct Toyota hose adapter rather than tap the existing housing. I called the manufacturer and spoke with them regarding the materials used. They informed me that the top cap part where I would cut into is made of plastic. After measuring, there is not enough material to tap a 1/4 NPT, so I'm stuck moving down to 1/8" NPT. I'm not confident there is enough depth of material there to provide a good reliable seal. Bummer. Waiting a week isn't the end of the world. I'd rather have it correct than fast.

 

[CO-Cygnus]

CNG Conversion... why?

 

[Jetboy]

Update: Put the air springs in. Had a few issues here and there. First problem was lack toyota oem air tube. I ordered one and got the wrong one. I received the one I ordered, but it wasn't the right one. Apparently there are a few different ends, so you need to make sure you get one of the two that actually goes into the spring, not one of the other 5 tubes that go different places.

BUT... if you're reasonably handy you can make up your own end. It's 5mm OD plastic tube. So... in the USA the closest thing you'll find is 3/16 fittings. Ace hardware has a lot more than a HD/Lowes kinda place. The portion that goes into the air spring is a tube section with a flange about 3/4" back from the end. A 3/16 compression band with about half ground off then used in a normal compression fitting will compress the band onto the 5mm toyota tube and makes a perfect end to go into the OEM airbag end.

The lower mounts are self explanatory. The crappy part is that it turned out to be way too tall. At the low end (40psi) I was still about a 2.5" lift. My goal was to be OEM height at low pressure and 3" high at high pressure. So... I'm making some new much lower height platforms - but I can still only drop at the most about 1". Maybe 1.5. So my low height will be about 1" high of the OEM springs. Of course with no pressure it'll be more like 2" low of oem height, but you can't really drive like that. It will be nice for hitching a trailer though. No need to use the tongue jack.

You can see the rest in the pics. I'll put some other pics in tomorrow once I get it dropped down where it needs to be for my goals.

 

[Jetboy]

Update. Today I made the new base brackets. The good is that they sit about 1.25 inches lower. At 50psi in teh airbags it's perfect height wise for what I wanted. I can drop another 3ish inches down to the bump stops if I want, but they're too soft at that level for me.

The downside is that I had to make them a simple single plate rather than a double level plate with an internal level. In the first version I could bolt them down to the axle so it couldn't come apart. In the second version there's no space for the bolt to hold it down in the middle.

I'll run them like this for a while.

In a perfect world I'd have a negative air spring to make a better balanced spring rate. They're soft enough I'll need a firmer shock to balance the softer spring rate.

 

[Antman]

 

[Jetboy]

Update: I took a trip to moab with these air springs. I can report that they work fantastic in the dirt. Unfortunately prior to my trip I had planned to install a wireless control box. Basically a home-brew compressor with a manifold, solenoids, and some circuitry for a delay timer so the two sides would have a few seconds after the height adjust to balance pressures, but my wireless relay board was the wrong one and I ran out of time to get another before I left, so I didn't have any on the fly adjustment.

Flex was much like coils - except the springs are just too tall. I'm really frustrated by that issue. They're no more than 1" spaced off the OEM height, but they are probably over 2" taller than I want. I can't really drop the rear down much below what would probably just be OEM height and it's sitting on the stops. In the pic below I'd really like to have at least 2-3" further drop down. GRRRR. So do I replace with generic springs or start cutting up the OEM spring mount on the bottom to get them to fit correctly? Not sure.

Otherwise they've been great. Ride is good. Adjusting up to tall height was great for Moab trails where the rear bumper likes to drag a lot.

Here's a high/low set of pics. My high limit is the shocks. I think the springs would actually go another 4-5 inches up if I had no shocks on. Not sure why you'd do that, but they have a ton of travel range. The front springs are currently about +2" from OEM. I'll drop them back to OEM height whenever I get around to it. I just jacked it up for Moab. Otherwise I prefer to ride low around town. They're adjustable coilovers so it only takes about 20 minutes per side to adjust the collars. The front is next on the list for coilover airbags.

I had to take my wife's scooter to get safety and emissions testing done. Yes -really... for a 150cc scooter. I hate these hitch carriers, but they do work.

 

[Jetboy]

Update:

I punctured one of the air springs this weekend. Not sure how. I've been running stock rear shocks and finally put in some long travel Fox shocks. During the re-inflate something happened that I cannot totally figure out I just heard the rush of air. And... there's a hole the size of a pencil through one of the air springs.

So out they came and in went the coil springs.

I think I'm near my end of this idea with OEM air springs. I think I may look at firestone or Goodyear bellows type air springs for a better replacement setup.

I don't know that I'd call it a total failure - but certainly didn't live up to what I had hoped for in terms of long term reliability. I suppose you could say I'm figuring out what everyone else already has...

 

[Doc_Fry]

Though I plan on doing airbags for when towing the boat. I am not planning in going as far as you.

Looking at putting in some firestone tyoe assister airbags that go in the sorings and are manually inflatable. But yhe benefits for me are when I have the rear loaded out when traveling or when I am towing my boat.

Costs for the assistance airbags are like $120.

 

[Jetboy]

I did not like the ride of the firestone airbags I had in my last 4runner. The design of a single bladder with no bellows or sleeve mechanism results in a support that is pretty stiff even at the minimum 5psi. I was looking for something better. For towing they work great. For the rest of the time I wasn't thrilled.

I still do think airbags have potential. I haven't found anything sharp that would have caused the failure. I think it probably was a tear from the bag its self folding incorrectly and then ripping as it was re-inflated trying to expand.

For best ride and adjustability I'd really like to have air springs with a negative chamber as well. So I can both adjust height and spring rates independently. That would require a piston type spring rather than a bag style air spring. And the problem becomes where to mount it and how to make it fit.

 

[FinnJ]

Has anyone done this? The only similar swap I've seen is this guy: Airsprung CNG äFJii - Toyota FJ Cruiser Forum

That’s me.

I've been running stock rear shocks and finally put in some long travel Fox shocks.

What FOXs did you put?

I think I'm near my end of this idea with OEM air springs. I think I may look at firestone or Goodyear bellows type air springs for a better replacement setup.

I don't know that I'd call it a total failure - but certainly didn't live up to what I had hoped for in terms of long term reliability.

Sorry to hear, mine GX470 bags have been fine for 5 years/75k miles now.

Did you ever measured the lowes/highest heigth of the GX460 bags?

 

[FinnJ]

What FOXs did you put?

I think I found it: http://www.toyota-4runner.org/2681620-post18.html
Looks like you have a similar setup, FOX 2.5 Factory series coilovers and 2.0 Performance series rear shocks.

I think the same way, rear FOX 2.0 shocks feel stiffer than fronts. Not a well matched pair. Now looking some better, maybe ICONs would work better. Any experience of Radflow or Fabtech with a progressive springs? (like airbags are)

I had Bilstein 5100 before, but then I didn´t had FOX´s coilovers. Then it was ”ok”, but now the front FOXs are much better.

 

[Jetboy]

That’s me.

What FOXs did you put?

Sorry to hear, mine GX470 bags have been fine for 5 years/75k miles now.

Did you ever measured the lowes/highest heigth of the GX460 bags?

I think the air bags are pretty well designed and durable. I don't know the max height of the GX460 bags - but I can measure them. I still have them in my garage. I might put them back in at some point in the future. What I can say for sure is that they have more than enough height to max out the extended length fox shocks. I think they have about 12 inches of travel, maybe more. They have a lot more than any coil spring that fits in that location. The limiting factor is the shocks and the suspension link geometry.

The other big downside is that the GX460 springs lack any internal bump stop. I did not ever install an alternative bump stop. I wanted to run near stock height on the highway and the lack of bump stops along with my 2" lifted mounting bracket meant that I couldn't really do that. I would bottom out frequently. I would ideally like to go back to a tipple bellow style air spring in the future that has an internal bump stop and the ability to compress a little further than the GX460 spring.

I don't know how much KDSS factors into my ride issues - the GX all have KDSS, but they use a complex self leveling system to adjust side to side. My system was passive leveling that used a solenoid to adjust side to side leveling by balancing air pressure with a delay relay - so when you'd adjust height, it would then open a valve between the left and right side air springs for 6 seconds to balance the pressure. The same when you lowered it. With KDSS it never sat very level because KDSS ends up needing about 200lbs more on the passenger side to balance the KDSS cylinder force.

My other crazy idea is to swap in GM autoride rear shocks. They are off of an option called the Z55 autoride - they are a combination of air shocks and magnetorheological shocks. And they happen to also be almost exactly the proper length to fit in a slightly lifted 4runner. I don't know enough about the magnetic function, but the intent would be to install a small dial on the dash with my own electronics to adjust dampening on the fly. And then also rely on the shocks for height adjustment along with relatively soft coil springs. I think that combination might work really nicely. https://www.ebay.com/itm/2000-2006-...d=381601610109&_trksid=p2047675.c100005.m1851

For now I'm back to 2" lift Dobinson springs.