Air Bags Over Coils

[SUMOTOY]

C/O issues - the numbers are in - long and nerdy

I know I shouldn't, but one more post, in case anyone other than Sumotoy is interested - the way factory air systems generally seem to be, you are limited to how fast you can go at max height.... Toureg...

WE:
Amazing you mentioned the Toureg, now you're well into my comfort zone, cuz I work on those in my shop and have the parts program for it as well. IFS? No, it's a multilink modified dual wishbone design, very much like the newer audis since 1998, and has a lot of height correction and antiackermann built into it. Although VW markets it well with all those stats you mentioned, if you read the reviews or drive one, it becomes obvious many folks equate ground clearance with articulation. Let's keep it on the 80, since after my measures today, I believe you too have also equated clearance with articulation.

Me and the boys tossed up my 80 to start taking some actual measures of the rods links, etc. After starting to gather data, a more obvious problem caught my eye. I believe the target is to increase ground clearance and articulation on demand with the coil over setup. Baseline = 0 (stocklike truck handling and height) Full battle regalia = +6in

The first problem I see is in the actual hardware. If you delete the internal spring bump, at rest on a stock truck, you have and overall curb weight resting height of 12 inches between the upper and lower spring mounts. That means to put in the aforementioned coil over in the truck, your maximum overall dimension of *all* components can't exceed 12inches. Ok, let's figure 3-4 for the bag hardware, maybe 1-3 for the perches and mounting. That leaves you with a 8in spring maximum, or more likely a 10in spring compressed at ride height.

Ok, now we have stock ride height. Let's go up 6inches and see what happens. At just under 4 we lose the rear swaybar, cuz it hits the axle. The front bar will also see interference at the front under articulation, so ditch that too. We also start to see a variance of 5/8 bumpsteer issue with the drop link in the front, that's also starting to laterally twist the control arm mounts front and rear. Pinion angle differences start to get dangerously high, because the rear upper links pull one way and the lower links pull the other, and the yolk angles gets severe. Ok add those CV axles from Slee. Now the brake rod is now at min bias to the rear brakes, because it's at the end of it's travel. Not sure the solution there on an adjustable suspension. Manual rear bias valve?

Where this coil over setup really starts to get interesting, is to the point I've been trying to get to all along: What's the target? I think it's extremely important that we clearly define that, because there is a big difference between lift and articulation. On a c/o bag setup (my design or the one pictured) you can only claim lift, not articulation. In fact, I'd conclude from just the measures I started taking, articulation would actually either stay the same or get worse than stock as you raise the 80 with that C/O setup. You have attained lift, as in water crossing, you haven't attained articulation, as in rock climbing. If you could quickly control the upside bag, maybe. I don't see that in the design, this design applied specifically to an 80 is a clearance setup, not at all an articulation setup.

Lift the 8in linear rate spring 6inches from stock, the numbers seem impressive. You have a theoretical 9inches of upward travel on either side of the front axle, and almost 11inches of upward travel on the rear. In reality tho, a lot of factors will affect that travel, the only one that really matters tho, is the above installed C/O. A 10 inch linear rate spring will hit spring bind at ~1/3 of it's length. That means that you will get about 3inches of upward travel on a 6in lift. you also have to tether the drop, cuz you can't have the spring leave the perch. Further reducing articulation. Yuk. Find some other spring? Ok, but to maintain stock ride height as a baseline target you are severely limited in what you can do there.

The ironic reality of this reduced articulation is pointed out in the offroad reviews of the Taureg air suspension. Even with a multilink suspension, lift conversion of a traditional suspension design for now is really only lift, the guy with articulation still wins. And if air lift is air lift, save 2400USD and call Airlift for the inserts. Or, seeing that you have to buy almost all the same Slee goodies to go up 6inches, why not just get the lift kit and get the articulation. Then you don't have to figure out how to move bump stops up and down with lift to control articulation.

Pick the poison, lift or articulation. If it's the former, no fancy hardware is necessary. If it's the latter, the fancy hardware might never find the target.

I have more measures of roll couples, cog, caster, bumpsteer front and rear so I can plug a truck into my car suspension program, but I really don't think it's necessary. I come to the conclusion that the C/O setup above creates more problems than it solves. YMMV, but there's a lot of old tech design in that 80 that prevents a lot of the new tech from meeting the minimums for a dual purpose variable ride height 80. My measures support my earlier conclusions on these components.

After staring at the insert setup I have on the truck, I think my next project will be to ditch the 113k shocks and drive around on just bags and springs. There's already tether holes right about where I need to put stop cables.

Nerd cap on

Scott Justusson

 

[SUMOTOY]

I've heard that the air lift folks are happy to help you find some that fit. They'll be for some other aplication - like a Ford van or super duty or something else that has tall springs.

I heard that too, in fact I was the one that wrote it up, including what mods are needed to do on the fronts. It's actually shorter than the rear, but it is a stock Airlift application. It does require that the spring bumps are removed and modified. Search the archives, it's one of my first tech posts. I believe the tech writeup was deemed 'worthless' within a few replies on the thread cuz it had no pics attached. Glad to see renewed interest, and I did post a pic fairly recently of the front bags installed.

SJ

 

[Walking Eagle]

WE:
Amazing you mentioned the Toureg, now you're well into my comfort zone, cuz I work on those in my shop and have the parts program for it as well. IFS? No, it's a multilink modified dual wishbone design, very much like the newer audis since 1998,

Remind me never to let you work on any of my cars. IFS - is Independent Front Suspension, unless there is a Dana 44 hiding under there somewhere, it's certainly not a solid axle. If it's not a solid axle it's IFS!

I don't see that in the design, this design applied specifically to an 80 is a clearance setup, not at all an articulation setup.

Did you bother to read any of the posts that it is forced articulation? Did you bother to look at the pictures of the FJ55 that show forced articulation?

I come to the conclusion that the C/O setup above creates more problems than it solves. YMMV, but there's a lot of old tech design in that 80 that prevents a lot of the new tech from meeting the minimums for a dual purpose variable ride height 80. My measures support my earlier conclusions on these components.

I've come to the conclusion that you are an idiot. What part of the suspension having a maximum compression and max droop and adjusting the ride height inbetween those don't you get. It doesn't create any issues that aren't there running through the normal travel anyway.

After staring at the insert setup I have on the truck, I think my next project will be to ditch the 113k shocks and drive around on just bags and springs. There's already tether holes right about where I need to put stop cables.

This confirms my conclusion.

The moderators are going to lock this thread anyway I'm sure

 

[Walking Eagle]

is this some sort of bizarre courting ritual....?

More like the Jerry Springer Show - you really don't want to spend any time on it, but once you've seen it, it's hard to turn away. At least untill that 400lb woman flashes the audience.

 

[SUMOTOY]

Remind me never to let you work on any of my cars. IFS - is Independent Front Suspension, unless there is a Dana 44 hiding under there somewhere, it's certainly not a solid axle. If it's not a solid axle it's IFS!

The marketing boys at vw/audi would have siezures about now. I meant to point out that it's a whole bunch more than IFS (ala IFS toyota), it's a multilink suspension IFS with a lot of engineering designed into it.

Did you bother to read any of the posts that it is forced articulation? Did you bother to look at the pictures of the FJ55 that show forced articulation?

Forced articulation happens on any airbag system. Is it more or less than an airbag insert vs a short linear rate spring. You can come to the conclusion that it can raise a truck 6in, as can an airbag insert. Both will force articulation to some extent. I suspect if one wanted to design more articulation into an insert, one could put the same pneumatic "accusump" on an insert system. But the advantage of spring length (drop) still goes to the stock spring in the stock truck.

I've come to the conclusion that you are and idiot. What part of the suspension having a maximum compression and max droop and adjusting the ride height inbetween those don't you get. It doesn't create any issues that aren't there running through the normal travel anyway.

I come to the conclusion that easy fixes never are. Coil overs are fantastic in a truck if you can run a long spring, or if you need to run them for space reasons. Compared to a separate spring/shock arrangement, they need a lot of spring length and shock travel to gain the advantage. Like you might find in this dual rate setup:
http://4wheeloffroad.com/techarticles/55358/

Put that on an 80 WE, you win the game in lift, articulation *and* dual rate/progressive spring. Otherwise, you have to consider lift and articulation on a 12in overall length. Given a 12 in overall length of a coil over in a stock 80, have you given thought to how much drop you can actually have? Think actual shock rod length inside that 12in strut.

The issues may present themselves in a stock truck, but it's the action of lifting the truck alone (no articulation at all) that we are speaking to. Minimally, you would have to disconnect the swaybars to go up 6inches from baseline. So, we ditch the bars. What does one do about brake bias? Are we speaking to lift or articulation? 2 different concepts. I'm not smart enough to see them as the same? Forcing articulation only requires air (bag insert, bag top, airlift shock). "Down" articulation is strictly a function of shock travel. How much of either relies on a lot of other variables.

Remount the whole kit and kabootle, and put in a really long spring, you can speak to articulation. Right now, you only speak to lift.

SJ

 

[Walking Eagle]

The marketing boys at vw/audi would have siezures about now. I meant to point out that it's a whole bunch more than IFS (ala IFS toyota), it's a multilink suspension IFS with a lot of engineering designed into it.

So, what you said was wrong - again.

Forced articulation happens on any airbag system. .

WRONG!!!! - yet again. If you have your inserts installed like Airlift says to - isolated from one another they are no different than a spring. Forced articulation only happens if you have a system plumbed and controled to do so. Unless you have a control like this

http://www.chassistech.com/AirbagDemo.html

or one of the game pads, or switch boxes that gives you control over individual corners - you don't have forced articulation.

Remount the whole kit and kabootle, and put in a really long spring, you can speak to articulation. Right now, you only speak to lift.

SJ

What kind of idiot would try to put a coil over where the current shock is or where the current coil is - I"m not sure which you're trying to get at, but it's going to require custom mounting - that's already been covered.

 

[Project FJ80]

Well, for what its worth, I am a diesel mechanic, and work on lots of onroad/offroad trucks that haul dirt/rock for landscaping.
The newer and nicer trucks run an airbag suspension. It gives you a smoother, quiter, less bumpy ride. It also lets you haul well over 80K lbs of material. with that being said, the Tractor/truck its self runs springs for the front tires, and you can occasionaly find bags on the rear, but they are a set ride hight. the Trailer runs airbags only, no springs... why? because theres no drive lines, only axles. Think about it... if you try raising your truck 6" with airbags, whats going to happen to the rest of your geometry? everything will bind, or drive shafts will fall out. The Reason why air bags work so well on Trailers, is because theres nothing to bind, no drivelines, no links, only Air brakes, plastic air lines, and airbags.. when you start up the truck, the airbags fill raising the rear suspension. There is no shocks or springs or anything else. When you go air suspension, you eleminate everything else.
on a stock LC, a 1-2" airbag lift option would be ok. anything more would require the removal of shocks, fabrication for the bags to go, an air compressor, air tank, air controll devise, and a set ride hight. if its not a set ride hight, it wont be very streetable, unless you only have a 1-2" change of hight.
LandRover uses airbags, with a fancy computer connected to it (for over 90K)
and ive always read that airbags are superior in ride quality, vs shocks and springs.
I can take picturs and post them if you would like, and if you were to drive a simi that is weighted with 30K on the rear with springs, then drive that same truck with airsuspension, you would never want to ride in the one with springs again.
Just my 2cents.
-Ron

 

[alia176]

For what it's worth, I just read the article on Four wheeler of the year, which happens to be the 06 100 series LC. One interesting note to point out is that the testers didn't care for the "high mode" on the Range Rover Sport. They mentioned that the ride is too stiff on the high setting, whereas, the 100 has a much better ride.

I can concur on the harsh ride quality of the RR on high setting but never been in a AHC suspended 100. The bags in the RR are pumped to a very high press for offroading and the occupants are beaten to death to some extent. It seems that the AHC on a 100 and on a 470 are totally different breed from the usual air suspension antics. They're pushing hydraulic fluid around the circuit to raise/lower the vehicle.

I'm enjoying this debate immensely. Please keep it up and leave the personal attacks out of it. You're an "idiot" type of comment is a little juvenile for this eclectic crowd; afterall, this is NOT Discoweb!!

Cheers,

Ali

 

[SUMOTOY]

From the horses mouth

Right, wrong, opinion... How bout some reality. Here's the notes I took from my lengthy conversations with the Universal Boys. Again, I'm only looking at WE original "option" in terms of the percieved goal: Stock ride height >6in lift.

First, the *only* thing you get in the FBSS kit is a set of 4 bags designed to run with an *existing* coil over setup. IOW, you own the coil overs, and you replace the helper spring with the airbag in that coil over setup. It's a 4-10inch adjustable donut with a hole for the strut tube. The donut goes *under* the upper spring perch, so the collapsed and extended spring/shock dimensions include the bag dimensions

I gave universal the application and the goal, they said, nutnuh. The problem (as I posted before) is that with a 12in coil over setup, you are using up 4inches of that for the airbag itself (that's it's minimum collapsed length). Which means exactly that the maximum main coil length is 6inches on a stock truck mount. They also doubted you will get all the 'advantage' of 6inches of lift, because of the overall short stroke of a 12 in shock. They also indicated that this is designed to be a replacement in an existing coil over, not really a coil over conversion, but it can be done. Rubicon is working on specific kits for the short dimension setups (like the LC), but currently there is no 2.5in spring application available (min for the big truck).

The picture shows a coil over setup with the airbag installed in it. The concept is to remove the helper spring, and insert the airbag in place of it. This allows a longer main spring, and gives adjustable ride height and progressive spring rate to the airbag coil over setup. It's just a direct replacement for the helper spring. Specifically, it's design is to replace the upper half of the setup on this pic
http://4wheeloffroad.com/techarticles/55358/

As I also suspected, the spring rate increases with ride height increase. In terms of articulation, "forced' articulation can use the exact same controller on 4 airbag inserts, the effect is the same. Again, you can claim to have more ride height ability with the airbag over the coil, but you can't claim (yet) to have more forced articulation. In fact, an airbag in a spring vs on top of it, will allow more forced articulation on the stock 80. Add in a standalone shock with 8more inches of travel, I'm still not with the conclusion that this setup has any advantage in articulation, maybe in absolute ride height, but 6inches of travel on a 12 in shock sounds... Optimistic, even to Universal.

There is a lot of demand for this type of setup in the guys that already have coil overs, and universal is developing a 2.5in coil over setup for the bigger trucks. Given the technical discussion I had with these boys, I'd be real interested to see the comparo of a airbag over coil adjustable suspension vs an airbag in coil adjustable suspension.

For now, suffice it to say, you can save a lot of money with Airlift bag inserts, and until someone proves otherwise, the same FBSS controllers on an airbag spring insert to a stock truck, should yield more articulation, and ride height. The limiting factors that need to change that advantage: Coil over location points to give longer effective length at rest, coil over shock extended length, and articulation interference.

What's your goal?

Scott Justusson

 

[SUMOTOY]

What kind of idiot would try to put a coil over where the current shock is or where the current coil is - I"m not sure which you're trying to get at, but it's going to require custom mounting - that's already been covered.

Ok, so this isn't a drop in like universal intended. I understand that now, hopefully others do to. Custom mounting? I see the possibility in the front of extending the overall dimension (with possible tire interference under max articulation). Given the goal of stock ride height, some more detail on the rear mounting might be a bigger problem.

I'm up for seeing if this could work. Right now this setup has created more problems on the 80 chassis than even universal can solve. I think the concept is awesome if you are already running a lifted truck with all the Slee stuff on it, then it makes sense (put coil overs in it to give it +5, add the slee drivability toys, then have the ability to raise +6 over that!) That sounds impressive and a much more practical solution to the 80 chassis in terms of fitment and articulation (but I'd read Christo's thoughts on 'too much' lift before I went up 11inches). I think the goal of stock height to +6 with this coil over setup is overwhelming and beyond the boundaries of the loosest definition of "stock" height truck.

Mercy

SJ

 

[SUMOTOY]

Around the water cooler at Universal today

A couple of interesting tidbits in my conversation with Universal Air:
* Universal is new to the truck 'lift' bag market, their main business is... Lowriders. ...Go figure
* I accused the tech guy at Universal of doubling the existing inventory by hitting the market with Lowrider in Reverse Theory (LIRT). He laughed and said he was sharing that one at lunch break...

SJ