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Air bag suspension chat


KKtrips

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the crown sits on about 70PSI at the front and 30PSI in the back for ride height. works well at these pressures.

the shocks are fairly aggressive but its not bouncy in any way. the only time it feels bouncy or nasty is when its right up and has heaps of air in the bags, like 80-90PSI.

 

im running firestone convolute bags with internal bump stops. same front and back. i needed something that could handle the angle changes that my suspension geometry dictates.

note with the firestone internal bump bags - Ride Tech list them on their website as being internally bumped, firestone will confirm this over the phone but they wouldn't give me any literature to say officially that they are designed to be used in this way.

this could cause you many issues come cert time if,

A ) you plan to use the bag as a bump stop

B ) your certifier wants manufacturer documentation to cover the bag being used as a bump.

 

i was lucky in that the certifier was happy to use the Ride Tech information as gospel. 

 

 

the slam spec bags have internal bump and are most common so certifiers know the name. 

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  • 2 months later...

That's not great if you have an engine-driven compressor is it?

 

Will check with cert man tomorrow.

 

Actually the rules let you be adjustable up to 20kmh or so IIRC, but I don't have an easy way to detect that, and don't want to get into building a speed-sensitive switch right now.

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This is what (some of) the rules say (from the pdf on the LVVTA website which ought to be up date) . I understand that people used to use the park brake warning light, but that isn't allowed anymore.

 

An air-bag system fitted to a low volume vehicle must be designed and installed in such a way that either:

 

(a) the air-bag system is only able to be operated whilst the vehicle is stationary; or

 

(B) the air-bag system can be operated whilst the vehicle is in motion, provided that:

 

(i) the ride-height of any part of the vehicle is electronically prevented from being adjusted or changed when the vehicle is being driven over a speed of 20 kph (12 mph); and

 

(ii) the vehicle automatically reverts to its pre-determined correct ride-height when a speed sensor determines that the vehicle is traveling faster than 20 kph (12 mph).

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I just put a switch in mine so that it would adjust in park, its just a switch on the firewall with a tab welded to the shifter arm

 

most cert guys aren't keen on ones that will let you adjust your height in neutral or the hand brake as it's pretty easy to just slip it into neutral or put the handbrake on a click and flick switches at 100kph etc

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This is what (some of) the rules say (from the pdf on the LVVTA website which ought to be up date) . I understand that people used to use the park brake warning light, but that isn't allowed anymore.
 
An air-bag system fitted to a low volume vehicle must be designed and installed in such a way that either:
 
(a) the air-bag system is only able to be operated whilst the vehicle is stationary; or
 
( B) the air-bag system can be operated whilst the vehicle is in motion, provided that:
 
(i) the ride-height of any part of the vehicle is electronically prevented from being adjusted or changed when the vehicle is being driven over a speed of 20 kph (12 mph); and
 
(ii) the vehicle automatically reverts to its pre-determined correct ride-height when a speed sensor determines that the vehicle is traveling faster than 20 kph (12 mph).

 

 

ay yep, all that sounds familar now that i read it again.

you could put a switch in the power feed that allows it to work only when the key is on "acc" and then with the simple flick of that switch you could have it working whenever the key is on and the motor is running. you know, if you had to have it working in two different ways for some reason...........

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Talked to Andy Smith today - he said linking it to the Neutral/Park switch will be OK. I'll wire it legit for the cert. Since I'm fitting a fancy ECU controlled one it might be nice for it to work while driving though.

 

I'll need to add a relay to the neutral switch circuit as the switch is just wired in series with the starter switch, which isn't very convenient.

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Hey just bought myself a 2000 range rover for towing duties as the air suspension is notoriously unreliable I've ditched it for coils. The ride now is not harsh but firm would this be calmed down by a set of new shocks? I'm guessing that airbags run different valving in the shocks. Kinda considering going air shocks in rear too to level it up 2 steps forward 1 back I know but on some level it does make sense.

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So, this is fully compressed bag at the rear. Am I going to have problems with the bag touching the flat mount plates?

 

At ride height the mount plates are parallel, but the angle changes a bit as the suspension moves up. It's only tacked for now, so I can change things if needed.

 

p1070459.jpg

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I just changed a set of bags which were set up pretty similar, after 2 years they were showing signs of chaffing and they would have popped.

I guess even when aired out they still have a bit of relative movement, or maybe it's from bottoming out when driving. It would be nice if the bags were designed so they couldn't wrap up past the mount face.

They don't seem to care too much about a bit of displacement at ride height so maybe the answer is to set them up parallel at bottom, or put a disc spacer under mount to give it some clearance.

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Cut the mounting plates so they are the same size and shape as the plates in the airbag. Then space them off so the bag can wrap around slightly if it wants.

If the bag touches the plate while aired out it's no problem, but it can not touch at any point while driving or eventually it will wear though. Make sure the plates are smooth and painted.

Ideally the top and bottom plates of the bag will be parallel at ride height. Some bags have an internal bump stop but I believe most don't, therefore you want to run a bump stop so when aired out the weight of the vehicle isn't on the bags. Having the plates crash into each other is obviously not what you want.

It's not the end of the world if you have to run the airbags offset at ride height. The bags will come with specs on how much is permissible under specific conditions etc. You may want to run them so they are slightly offset at ride height and slightly offset in the other direction at full slam if your suspension setup sees a lot of angle change from one extreme to the other.

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  • 7 months later...

That sounds a lot better than having variable resistors on lca's and letting electronics do it.

I would rather do it manually. Who cares if it takes a bit more flicking switches, it's mean.

lol the 5 years ago me is an idiot.

I should have been banned.

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