Defender Airbags v coils. Final verdict

The pressure resulting in air springs when they are compressed or extended depends greatly up where the static ride height was, and the air pressure at static height.

When an air spring is anywhere close to full extension, they don't like much pressure. With no cross linking that problem won't occur, because the pressure drops as the trapped volume increases during extension.

The issue with cross linking is the the compressed side air spring increases the pressure in the extended side air spring. That would be ok for limited axle articulation but bad for the life of the bellows for large articulation. IMHO don't do this.

Forced articulation (linking front and rear) would be good, but simple ways of doing it are difficult when payload is so variable.

Quote:

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Originally Posted by Dougal

Sproklegrommet - Self Leveling DIY Air Suspension

Anyhow, at dougals rate it will be 2056 before he tries anything:D

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2020 easily. I don't apologise for having a life competing for my time and money outside rovers.[/QUOTE]

Dreams are cheap:p

I'm not all that clever, but I've actually tried most these ideas in the real world

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Originally Posted by rick130

I don't think anyone would have stressed them anymore than Tony/Rangierover in his 120.
It's his farm hack, do anything, load anything in any conditions vehicle.

How is it going ?

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IIRC Tony had a bellows fail due, it appears, to being pinched between the spring perch on the chassis and the bottom plate of the airbagman spacer.

I suspect (from seeing the photos) two issues with how the air spring was mounted that contributed to the failure:

(1) the design of the spacer is not good IMHO. Its width is approximately equal to the diameter of the end closure crimped to the bellows, which leave a gap between it and the spring perch where the bellows was being forced when the air spring was fully compressed (axle on bump stop).

(2) the edges of the plate were not rounded off, leaving an edge that wore the bellows. IMHO the plate should extended right across the inside of the perch so there are no gaps or edges to abrade/pinch the bellows, just a flat surface to roll on.

Firestone recommend a minimum pressure when the air spring is fully compressed, and I do wonder if all of the air may have been dumped when the airsprings were lowered to the bump stops.

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Originally Posted by Bush65

The pressure resulting in air springs when they are compressed or extended depends greatly up where the static ride height was, and the air pressure at static height.

When an air spring is anywhere close to full extension, they don't like much pressure. With no cross linking that problem won't occur, because the pressure drops as the trapped volume increases during extension.

The issue with cross linking is the the compressed side air spring increases the pressure in the extended side air spring. That would be ok for limited axle articulation but bad for the life of the bellows for large articulation. IMHO don't do this.

Forced articulation (linking front and rear) would be good, but simple ways of doing it are difficult when payload is so variable.

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The main point, being don't fully extend or pressurise your bags at full suspension travel.

Interestingly the stock RRC bags only have ~165mm of stroke between fully seated and bulged (vehicle on bump-stops, level ground) and fully extended (vehicle on trolley jack, wheels in the air). At high ride height it sits level 45mm below full extension and 120mm off the bump-stops.
P38 bags are allegedly shorter again.
The L322 has something like 11 inches of front suspension travel and more in the rear.

The challenge is to fit longer bags without them fouling anything else.

Thanks everyone for the feedback.

So this is a go ahead for me - I am only doubting the controlling system now.

Ive had a few quotes returned to me and to say that Im not very impressed with figures is an understatement.

Saying that though, Airbagman's level of knowledge shown, along with the very personalised email was pretty satisfying. Im not quite ready to outlay the $ yet, at least until I know how I will control it.

AccuAir's e-level system was mentioned in one quote. Does anyone have anything to say about it?

Part numbers for Air Bagman AB0051.
Firestone part number: W01-358-5422
I would look at Air On board for tank and pump and control valves. at least their tank has a drain port on it.

Albert posted that Airbagman use Firestone W01-358-5422 air springs. So I pasted some comparisons from a catalogue - first pic.

The top air spring shows some details for the W01-358-5422. It uses a 1T14C-3 bellows with an internal bump stop, and a 3.62" high piston. IMHO this is a good candidate for the rear of a Defender.

The next air spring uses a 1T14C-7 bellows without internal bump stop, and the same piston. Note the difference in max height is 4" = 7" - 3" (see where -3 and -7 are in the bellows number). Also note the difference in minimum height, due to the internal bump stop. For our vehicles, you should use the external bump stop and not rely on the internal. For no internal bump stop, the external bump stop should be set to limit the minimum height similar to if it had an internal bump stop.

The last air spring is what a few members have used with success. The difference in maximum height is due to the -7 bellows and a taller piston. The difference in minimum height is due to the taller piston.

All 1T14C-? bellows are similar apart from height (the -? part). Internal bump stops and differences in the closure plate at the top, which were changes made to suit different customer's installations (these are replacement air springs for OEM's). The -? can be -1, -3, -5, -7, -8. IIRC, one member here, cal415, is using -8 bellows in the rear of his 130.

The next 2 pics show the problem Tony had with the bellows pinching at the top.

The last pic relates to my earlier post about not to cross link air springs, it is the data sheet for an air spring with the 1T14C-7 bellows and 3.82" high piston. The shaded area on the left, from 17.4" to 20" is marked do not use in this area without consulting Firestone Engineers (or such like). At these extensions Firestone recommend very low loads on the air spring, and hence low air pressure. In this range the bellows is unrolled or close to unrolling from the piston and the effective area is diminishing quickly. The air springs that Land Rover use in RRC and P38 are a different style and construction to these Firestone air springs.

Thanks John.
So next question.

At full axle articulation, how much spare capacity do you need in the bag over the same length on a completely straight extension to account for the angle of the axle?

Is it enough to make sure the longest diagonal doesn't exceed the normal max length?

[QUOTE=Bush65;1938321]Albert posted that Airbagman use Firestone W01-358-5422 air springs. So I pasted some comparisons from a catalogue - first pic.

The top air spring shows some details for the W01-358-5422. It uses a 1T14C-3 bellows with an internal bump stop, and a 3.62" high piston. IMHO this is a good candidate for the rear of a Defender.


These are the ones I have,I got the airbagman kit and onboard control kit.

The kit also came with 25mm spacers for the external bump stops.

The backup and support from the Airbagman was fantastic.

The posts by Bush 65 on Chooks Defender 110 regarding rear suspension heights helped solve my initial handling problems(I was setting the rear ride height too high)

Jim.

The other big question is what shocks should I be using?
I have a set that came with the 86 county, +2" dobinsons. I have a fair amount of wieght onboard and it has a fair bit of wallowing and a good dip will keep it bouncing a few times. Not bad but I think it should be better with stiffer shocks?
Any thoughts