setting the ride hight with air bags

[sqweaka]

hi all, ive installed 6" firestone airbags in a xjs front clip on my 49', because of the pivot point of the A arms on the jag clip ive 12" of lift from the floor to full lift... on the rear im installing a home built four link setup with firestone sleeve type bags which have a 6" lift but because they will be closer the the axle it will only lift by the 6"
the four links need to be set level at ride hight, question is what is the inflated hight i should set the rear bag at... if you see what i meen
if its got 6" of travel do i set it at 2 thirds of its travel to allow both up and down movement as you travel down the road

[dsraven]

set the truck on stands at ride height and block it there. some guys actually weld up some dummy shocks to keep it at that height even if it gets bumped etc. get the pinion angle set up and wheel alignment set close. make sure all axles are parallel etc, with a fully adjustable 4 link this can be critical. check the specs on the bags to see if they have internal snubbers and at what height the snubbers touch-if equipped. then decide from that info what you will do for set up of the bag. are you looking to lay it on the rockers or just wanted air bags for ride quality and adjustment? I would personally have more travel for the axle going into compression, over a bump, than under extension. remember to check if you will need a c notch for the axle and ensure you have travel for the shocks as well.

[dsraven]

got a pic of that set up? that may help.

[sqweaka]

no pics at the minute...i want it lay on the ground when air'd out yes, ive notched the frame at the rear to clear the axle, the bags dont have any bumpstop built in to them.
most of the builds ive seen, seem to have the bags fully inflated at ride hight, but does that not give a hard ride and does it not do harm to the bags as there is no room for them to rise any further over uneven surfaces!
should they not be slightly under inflated at ride hight, if so by how much

thanks ian

[sqweaka]

heres a link to the bags i have for the rear...

http://www.truckspring.com/suspensio...rite-9001.aspx

[lolife99]

Go to the air bag manufacturers website.
They will give you the measurements you are looking for.
With the Firestone F9000 sleeve bag below,... you would set your upper and lower bag brackets 8.25" apart at ride height.
(4-link bars parallel to the ground with the pinion angle set)

[Valarius_Starchaser]

Extended Length (IN):8.37 inches
Ride Height:6.38 inches
Maximum Diameter:5.70 inches

That was kind of right on the page you linked....

The fronts should have the same info

[e015475]

I'm no expert, but here's what I did/am doing.

I'm using Slam RE5 bags on the rear, not Firestone, but they should be similar.

At the normal ride height for the truck, the upper and lower air bag mounting plates are parallel. (front and rear)

The travel of the airbag is 5", and at the normal ride height it can compress 3" and extend 2"

The motion ratio of the rear wheel to the airbag is about 1.25:1 giving me a overall suspension travel in the rear of a little over 6" - about 3.75" up and 2.25" down

For the front, I'm using Slam RE6 bags, The Jag front has a motion ratio of about 2:1 and the bag stroke is 8", so there's a little more flexibility.

The bag has an internal bump stop at 2.9" and will be spaced between the pocket in cross member and the lower control arm so it hits the bump stop with the front cross member about 1" off the ground. If I have a total failure of the air system, I want to at least be able to move the truck, with the air bag fully deflated and resting on the stops. (the rear end is the same way except the limit is set where the half shaft will hit the frame rail)

At normal ride height, the Jag's front cross-member is a little more than 6" off the ground, so the movement of the air bag between the loert bump stop and the normal ride height will be 2.5" [(6" -1")/2=2.5"] At the wheel, the suspension will move 5" up from the normal ride height (2:1 motion ratio)

So if the total stroke of the front airbag is 8" and 2.5" is used in compressing the it, there is 5.5" left for downward movement - which is 11" of wheel travel downward - much more than is needed. I figure I only need about half of that or about 6". So for the front, the bag will compress 2.5" and extend about 3" for 5.5" of bag stroke total. At the wheel, there will be about 11" of travel (5" up and 6" down)

Planning on experimenting with the factory Boge shock and see where it limits the downward travel and if I can use it - I don't want the front suspension hanging from the air bags when the truck is jacked up. If the Boge doesn't work, a lot of KYB shocks have limit stops in them and perhaps one of those will work.

Jeez, I hope all this rambling on makes sense. Like I said, I'm no expert and would like to hear about others air bag setups too.

Phil

[e015475]

I thought this air bag set up for a Jag IFS was well thought out. Look at page 14

http://www.jalopyjournal.com/forum/t...451036/page-14

Phil

[sqweaka]

wow thanks for that phil on my jag set up on the front ive left the factory upper bump stops in the arms and when you jack the truck up it his these before the bags are fully extended,
i think the front set up will work fine on mine, as you say you have much more suspension movement because of the pivot ratio,

lolife99 that image only shows a total travel of 4"... that cant be right?

[lolife99]

Originally Posted by sqweaka

lolife99 that image only shows a total travel of 4"... that cant be right?

I quickly pulled that pic off the internet.

Like I said,... go to the Manufacturers website.
Get the info you need.

THis pic was pulled off of RideTechs page about Firestone air bags,...

[sqweaka]

sorry keith.. thanks for the help here, been googling and i cant find a firestone web page showing the spec of bags... ill keep looking
just had a quick measure of the bags i have
fully extended 12"
deflated as in the pic's above 7"
completely sqwashed 4.25" (but i dont think they are ment to go that far down in operation as the bag is all deformed and out of shape)