Airbag Air suspension

SkiFreak

Crazy Person
I have seen some trucks being setup this way (normally at the rear), but there are potential issues when it comes to greater articulation, so if you are planning on going down this route you really need to do your research.
 

DzlToy

Explorer
The Isuzu NPR built by Angry Iron for NeverQuit Overland had air bags for load leveling in the rear. The third truck, and last truck built by that shop had air bag leveling on all four corners.
 

Ultimark

Active member
As someone who has fitted air an bag kit to a light commercial vehicle, (Isuzu D-Max cab chassis with a tray at the rear) then used it for the last 14 years; it may or may not be ideal.

I have actually crawled underneath that truck shown in that video, impressive bit of gear, as is the price. But it is what it is. That particular truck has parabolic springs fitted on the rear, I cannot remember about the front but I believe it has parabolic springs on the front as well.

The idea is for the air bag accessory kit to help with corrugations on the roads and to a point, to help with the overall load. The owner is enthusiastic about the kit and reckons that it is much better to drive on sealed roads and dirt roads.

All Terrain Warriors, who originally converted that truck parabolic spring suspension wise, have fitted that air bag kit to their personal Isuzu 75/155 trucks. They believe that if you can afford it, it changes the truck enough to be worth it.

Essentially air bag kits of this nature, are enhancements to the suspension system when you are overloading from a normal load to near the maximum allowable load of your vehicle. If you need to use an air bag suspension kit all of the time, then your standard suspension really needs looking at.

On our D-Max utility vehicle, we put a slide on camper on the rear tray, then pump the air bags up slightly, from normal 0.8 bar when the vehicle is unloaded, to 1.8 bar when fully loaded with the camper. This is the general idea of air bag assistance. If you need air bag assistance all of the time, then this suggests that your base suspension system is not correct.

On our Isuzu 75/155 4x4 NPS, we only have parabolic spring suspension front and rear. I closely looked at air bag assistance, but the changes would only be incremental, not fantastic. Essentially a diminishing returns situation.

Another aspect is suspension limitations from fitting air bags. In the case of the Isuzu 75/155 NPS, I believe there is a reduction in wheel arc travel. Our All Terrain Warriors parabolic spring suspension combined with their supplied aftermarket dampers, allows a 600mm arc of travel. Which really allows the vehicle to work very well in interesting terrain. Our little truck is very comfortable with the suspension system and although there may be an incremental difference in comfort, I wouldn't like to change ultimate comfort for ability.

The below picture, which I believe I have posted before, shows our axles at their maximum articulation, at the same time you can see the chassis twist by the difference between the cabin and the camper. Our spring mounted tray was also getting near it's limit as I could hear it groaning, which it only does as chassis flex nears maximum.

To help you somewhat, an approximate cost of the kit you see on that truck in the video, not installation costs, is this.

Air bag kit for a generic Isuzu 75/155 which may be slightly different depending on any brackets required, $3,000 AUD

The switch kit shown, which enables each individual air bag to be raised or lowered, is somewhere between $800/900 AUD.

These prices are very loose and around a year old. Once an individual requirement is designed for a particular vehicle, then a final pricing can be finalised.

I hope this helps and the translator works correctly for you.

Mick.

Front_Live_Axle_003.jpg
 

DzlToy

Explorer
Do you mean that the distance from the top of the tire when stuffed into the fender well to the top of that tire when it's drooped as far as it will go, is 600 mm? That is nearly 24" of wheel travel which is quite impressive if the airbags are still fitted to the truck and allow this much travel.
 

Ultimark

Active member
No we don't have air bags, they restrict articulation and as a result you get wheels hanging in the air way before you could if you didn't have air bags.

The 600mm of articulation is this: the top of the tyre rises somewhere between 280mm to 300mm and the bottom of the tyre drops the same from its respective high and low extremes from a static position.

I too was sceptical about this relatively extreme articulation on what originally was a Japanese designed and built city delivery truck. Admittedly the NPS is designed with different suspension, transmission and some other pertinent stuff from the original delivery truck configuration; but the changes All Terrain Warriors make, is really a job well done. Interestingly, they are always changing and adding or subtracting components to their list of what is available. The air bag possibility is but one of those changes/additions, which wasn't available when we purchased ours.

Attached is a straight picture of the drivers side front wheel in a static position, note the distance above the tyre to the cabin. Then check where the passenger side front wheel is in the dynamic picture I posted above. Remember these are live axles, so if one wheel goes up, the opposite wheel on the other end of the axle, must go down.

When I was wondering whether or not we could squeeze in an aftermarket Centralised Tyre Inflation System (CTIS) I drove one front wheel up a ramp until the front axle had no more possible movement, then took measurements. The accepted articulation figure I could determine upwards was hovering around 280mm to 300mm, with obviously the drop on the other side being the same. The CTIS hard air pipe runs extremely close to the underside of the cabin, but it just fits; mostly.

On full lock and with extreme articulation, the CTIS hard pipe just scrapes on the underside of the cabin. Both CTIS hard pipes have slight scratch marks, but that pipe is so hard you can hit it with a steel mallet while it is on a steel bench and you are pressed to find where you hit it. It's part of the reason this product is very successful in this country.

I could restrict the steering lock; there is a bolt sitting on the front axle that allows one to do this, but I haven't.

Mick.

IMG_20221113_130027.jpg
 

DzlToy

Explorer
That is how the Yanks measure articulation as well. As I have never heard of 24" of wheel travel on an NPR/NPS, I thought the Aussies may use a different standard. Thanks for the clarification.
 

Ultimark

Active member
DzIToy, I Just had a thought after reading your take on Isuzu NPR/NPS wheel travel, presumably from an American perspective.

All Terrain Warriors (ATW), essentially take an everything approach, which you can have, or you can have a restricted approach. In 2019, which is when we started talking with ATW, there were various options we could get for the vehicle to do what we wished. Our vehicle, is basically an everything approach.

The original reason we were looking at these units was to place our existing slide-on camper from another vehicle, which after 10 years of sand dunes and corrugations had started to fall apart. Having extra carrying capacity and extra room for whatever we wished to carry was going to be a bonus. It also meant that were weren't right on the legal maximum weight limit as we were with our utility vehicle.

The first question they asked was what terrain we wished to travel over, followed by, "are you wishing to tow?" Understanding that we were going to have a vehicle that was designed for 7500kg as a 4x4 from the factory, but were only going to be running at an estimated 6000kg when fully loaded, the suggestion was put to me that perhaps I would be interested in the 17" wheels fitted with 37" tyres. The complete suspension change, which includes an approximate 50 to 60mm body lift, then allows them to configure this extreme articulation possibility.

The downside of this wheel/tyre suspension combination, was a lowering of the Gross Vehicle Mass (GVM) from 7500kg to 7000kg. In general our GVM is always slightly under 6000kg when fully loaded, so the capability of the vehicle is excellent, not brilliant, but certainly has allowed us to travel to some interesting places with relative ease.

As a point of interest, we sometimes run fuel and water quite low, the difference over a weighbridge which happened to be handy once as we did a there and back 15 day trip, was approximately 460kg lighter. Having CTIS fitted to the vehicle allows us to adjust or trim the front and rear axle air pressures to accommodate the change in GVM, which is something we never would have thought of prior to having the CTIS fitted. After refuelling and taking on water, we just press a couple of buttons and we are back to correct pressure for the changed GVM.

Without the body lift, I doubt very much you could still have 600mm of articulation with tyres that are 940mm high by 340mm wide. It really is a marvel how they've done that. So this vehicle is certainly very different to a stock NPS, and way different to the NPR in Australia.

In Australia out of the three Japanese 4x4 light trucks that are available, Canter, NPS and Hino, the Canter is the smallest/lightest and most nimble. The Isuzu 75/155 is larger in most aspects over the Canter and only comes with a single wheelbase option (medium). The Hino is the largest of the three, has unbelievable brakes (all disc) but is almost unseen in this country. I've only ever seen one Hino, a crew cab unit, and that belongs to a niece and her husband and their 4 kids.

Mick.
 
DzIToy, I Just had a thought after reading your take on Isuzu NPR/NPS wheel travel, presumably from an American perspective.

All Terrain Warriors (ATW), essentially take an everything approach, which you can have, or you can have a restricted approach. In 2019, which is when we started talking with ATW, there were various options we could get for the vehicle to do what we wished. Our vehicle, is basically an everything approach.

The original reason we were looking at these units was to place our existing slide-on camper from another vehicle, which after 10 years of sand dunes and corrugations had started to fall apart. Having extra carrying capacity and extra room for whatever we wished to carry was going to be a bonus. It also meant that were weren't right on the legal maximum weight limit as we were with our utility vehicle.

The first question they asked was what terrain we wished to travel over, followed by, "are you wishing to tow?" Understanding that we were going to have a vehicle that was designed for 7500kg as a 4x4 from the factory, but were only going to be running at an estimated 6000kg when fully loaded, the suggestion was put to me that perhaps I would be interested in the 17" wheels fitted with 37" tyres. The complete suspension change, which includes an approximate 50 to 60mm body lift, then allows them to configure this extreme articulation possibility.

The downside of this wheel/tyre suspension combination, was a lowering of the Gross Vehicle Mass (GVM) from 7500kg to 7000kg. In general our GVM is always slightly under 6000kg when fully loaded, so the capability of the vehicle is excellent, not brilliant, but certainly has allowed us to travel to some interesting places with relative ease.

As a point of interest, we sometimes run fuel and water quite low, the difference over a weighbridge which happened to be handy once as we did a there and back 15 day trip, was approximately 460kg lighter. Having CTIS fitted to the vehicle allows us to adjust or trim the front and rear axle air pressures to accommodate the change in GVM, which is something we never would have thought of prior to having the CTIS fitted. After refuelling and taking on water, we just press a couple of buttons and we are back to correct pressure for the changed GVM.

Without the body lift, I doubt very much you could still have 600mm of articulation with tyres that are 940mm high by 340mm wide. It really is a marvel how they've done that. So this vehicle is certainly very different to a stock NPS, and way different to the NPR in Australia.

In Australia out of the three Japanese 4x4 light trucks that are available, Canter, NPS and Hino, the Canter is the smallest/lightest and most nimble. The Isuzu 75/155 is larger in most aspects over the Canter and only comes with a single wheelbase option (medium). The Hino is the largest of the three, has unbelievable brakes (all disc) but is almost unseen in this country. I've only ever seen one Hino, a crew cab unit, and that belongs to a niece and her husband and their 4 kids.

Mick.
First of all, thanks for your comments Mick
Is there no way to separate the tire extension from the operation of the air spring suspension? I'm all ears, thanks.
 

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