Rear airsprings - inflation/control options

[steveG]

I've been doing a lot of reading here on airsprings for the back of a Defender, and providing I can get my engineer to play nicely - intend on fitting them to a future 130 project.
Seems those who have them fitted are generally happy, but I haven't found too much on how people are controlling them.

What is everyone using - manual inflation through schrader valves, manual control valves, or some sort of automated levelling system?

For manual inflation are you just levelling by eye/measurement or some other method?

Also, if you've changed systems for some reason (or would like to) what are the reasons?

Steve

[DiscoMick]

I've been planning to copy several people I know and just get the airbags for the rear with valves for pumping up using an external compressor, as this could be good when towing the camper trailer.
While the automated systems are good when working, I'm the kinda bloke who likes to keep it as simple as possible, so I think just having a compressor in the tool box is less likely to fail than having it permanently mounted with lines running around the vehicle, but I could be wrong.
Be interested in what others think about this.

[130man]

Hi Steve, I use a Schrader valve mounted near each spring and out of the path of dirt. Easy to reach but out of immediate sight behind the mudguard on the aluminium tray. I have an electric air pump in the cabin and the hose easily reaches both rear springs and it takes very little time to change the air pressure in each spring. I judge the height of the spring by sighting across the top of the tyre to the spring bracket on the chassis. Simple and straightforward. It must be done with the vehicle on a level surface or it is not accurate. Measuring the air pressure in each spring is another way to do it but does not allow for unbalanced loading of the vehicle. I connected the air spring to the Schrader valve with a short length of half inch air line, which I reckon will be quite stone resistant. Cheers, 130man.

[isuzurover]

I have a Sanden OBA compressor which is permanently on [connected to pressure switch]. This is connected to air tanks and a feed for the [rear only] air springs comes from there and goes to each rear spring via a separate [manual] needle valve / pressure regulator.

[LoveMyV8County]

I had the Schrader valves protruding from the crossmember below the 110's rear door, and just used an external compressor when required. With the heavy LPG tank on one side I used different pressures in the two airbags and levelled by sight like 130man. Simple is reliable!

I also carried a bicycle pump in case of emergencies, such as when the air line at the servo let all the air out the bag and refused to put any back in, but it is bloody hard work to pump them up manually!

Chris

[steveG]

I have a Sanden OBA compressor which is permanently on [connected to pressure switch]. This is connected to air tanks and a feed for the [rear only] air springs comes from there and goes to each rear spring via a separate [manual] needle valve / pressure regulator.

Not sure I understand how that works. Could you explain a bit more?

If initially inflating/setting the bags, do you have to open the needle valve and then set the pressure with the regulator, then close the valve?

Or is it a case of setting the regulator for the required static pressure (height) and the needle valve acting as a restrictor to stop pressure from bump compression etc venting through the regulator?

Steve

[isuzurover]

Not sure I understand how that works. Could you explain a bit more?

If initially inflating/setting the bags, do you have to open the needle valve and then set the pressure with the regulator, then close the valve?

Or is it a case of setting the regulator for the required static pressure (height) and the needle valve acting as a restrictor to stop pressure from bump compression etc venting through the regulator?

Steve

What I use are basically mini versions of industrial compressed air regulators. I only ever have to touch them if I change the vehicle load significantly, or want to load stuff on the roof more easily.

So the air tanks may be normally at ~100 psi and the air springs may be ~50 psi (for example). I can dump all the air from the air tanks and the air springs stay inflated.

The regulators do vent a small amount of air on compression, but only offroad-cross axle type situations. If anything this would improve articulation slightly over a schraeder setup.

[steveG]

Ahhh - that makes sense.
Still not sure what the needle valves are for though, and whether they are on the tank or spring side of the regulators.

Your system sounds very simple but also aligns well with the Vicroads modification guide for replacing coils with air springs which has specific requirements about:

• receiver for continued supply to springs if compressor fails
• indicator to alert driver of compressor failure
• preventing the ride height of an individual axle/wheel from being adjusted whilst in motion

I was initially thinking about just the manual schraeder valve setup for simplicity, but a setup like yours would make it much easier to achieve the requirements without having to argue technicalities.

One of the features I want to have is have some sort of dump/squat function to enable lowering the vehicle out from under the camping pod I'm planning to build.
If I've understood correctly that could still be done with your setup but would ideally need either the pressure in the tank drained first or some sort of shutoff valve in the regulator supply to save having to dump the entire system air volume out of the "squat" valve.

Steve

[isuzurover]

...


One of the features I want to have is have some sort of dump/squat function to enable lowering the vehicle out from under the camping pod I'm planning to build.
If I've understood correctly that could still be done with your setup but would ideally need either the pressure in the tank drained first or some sort of shutoff valve in the regulator supply to save having to dump the entire system air volume out of the "squat" valve.

Steve

It is just a simple twist of each reg to dump all air from the springs and squat the rear down to the bump stops. The tanks remain full.

[steveG]

What pressure rating are your regulators?
150PSI supply pressure rating would be plenty high enough for the actual supply, but is there a need to use something with a higher rating to cope with the pressure coming from the air spring compression over bumps etc?

Steve