how well do bags handle?

[(joey)]

i have come across a few handling threads lately and since im doing a bag setup i was wondering how do bags handle?and what air bag setup people have for handling?

[blitz'd]

That is like asking how springs handle. It is all dependant on how it is put together. Bag placement, shocks, sway bars, bag type, etc. They can handle just as good as anything with the correct setup.

[robnolimit]

Good answer. An air bag is infact an "Air Spring" in it's purest form. If the bag is mounted correctly so that it is in it's "sweet spot" at ride hieght, and the correct bag is used (load rate), so that the air pressure at ride hieght is in the 80 - 100 psi range, then you can have great handling with a bag. We build all of our performance air suspensions to use a 3/8" spacer in the bag mounting, so that we can add, or subtract spacer thickness to 'tune' the effective spring rate at ride hieght. After that, it's all shocks, swaybars, and set-up.

[(joey)]

thanks guys.thats what im looking for.i knew the bag was like a spring but was not sure what the compression and rebound was like.if it would act like soft rate spring or hard?or if diving into a corner would cause the rubber on a bag to expand under pressure.also wondering where to mount the bags in the rear,arms inside the frame or out side of frame?how to run the bags for cornering?enough pressure so the bag doesnt bottom out when the body rolls or just enough so it bottoms out at a certain sweet spot?should have explained more in my first post.

[robnolimit]

Joey, what are you building? yr, model, motor/trans.....

[(joey)]

67 gmc short box swapping onto a shortened 01 sierra frame/running gear.4.8l with some goods and after all the bugs worked out a single or twin turbo.i plan on using a t10 trans.minor upgrading the stock disc brakes in all 4 corners to start off ...im just trying to plan out the suspension so i can tackle it after the body is finished.

[N2TRUX]

Originally Posted by (joey)

67 gmc short box swapping onto a shortened 01 sierra frame/running gear.4.8l with some goods....

Oh I gotta see this. You can't just throw that out there and not show us build pics.

[SBTork]

^^ yeah really, we need more than that. Pics pleez

[(joey)]

im going to start up a build thread real soon.i had the project for 2 years and it got set to the side for quite a while.i started back at it again with bigger and better plans.i already have the 01 sierra and im deep into the body mods/repairs of the 67 right now.

[steppside69]

Any teaser pics? Eric

[67cheby]

i would like to jump in with a question along these lines, mine is a 67 chevy swb, dropmember up front with sway bar, rear PB 4link bags behind the axle on the outsides of the frame, and a KP components watts link, my question is do i need to run a rear sway bar also to make it corner better ??

[N2TRUX]

Originally Posted by 67cheby

...., my question is do i need to run a rear sway bar also to make it corner better ??

Maybe, but you should consider something that is fully adjustable. From what I have been reading, adding too much down-force on the rear can be more detrimental to a neutral truck that too little.

Something like this is what I have in mind...LINK

[67cheby]

something like that was actually what i was considering, i know so little about setting up suspensions, i guess one of my other questions is does the watts link in some sort act as a sway bar ?? or does it just center the rearend

[stich626]

Originally Posted by robnolimit

Good answer. An air bag is infact an "Air Spring" in it's purest form. If the bag is mounted correctly so that it is in it's "sweet spot" at ride hieght, and the correct bag is used (load rate), so that the air pressure at ride hieght is in the 80 - 100 psi range, then you can have great handling with a bag. We build all of our performance air suspensions to use a 3/8" spacer in the bag mounting, so that we can add, or subtract spacer thickness to 'tune' the effective spring rate at ride hieght. After that, it's all shocks, swaybars, and set-up.

well thats great.. at ride height you have your spring rate.. but unlike a spring the airbag looses rate a the wheel drops and gains as the wheel goes up.
as the bag opens up (wheel down) the psi drops (correct?)
how do you tune for that as no road or track is glass smooth

in the rear under brake'n the spring rate would be nothing like it's ride height at stand still.. with all the weight moving toward the front wheels..
how does one tune for all this..

[tcb-1]

actually my "old" rig handled MUCH better on air than with the KYB's, CPP springs, and a meaty front sway bar.

[robnolimit]

Stich, you are correct. Mant have tried to make a perfect spring, which would have an increasing spring rate as it compresses. Variable rate springs have not been so successfull due to the pre-load at ride hieght. With air, as you compress it at ride hieght, the effective spring rate rises, and thats a good thing. As you unload it, it becomes softer. Years ago we tried to add small tanks plummed into the bags, to act as a resivour and add to the volume of air, and reduce the change in pressure as it is compressed. It works great on a spring rate gauge, until you bring "time" into the equation. Real time testing showed that even with 1" line, by the time the pressure equalized, the bump or turn was over. Start tuning by choosing the correct bag, one that will be at 80 - 100 lbs at RH, with the bag in it's posted sweet spot. Minor corrections can be made with shim spacers, usually 1/4" alumn. and air pressure.

[robnolimit]

Maybe, but you should consider something that is fully adjustable. From what I have been reading, adding too much down-force on the rear can be more detrimental to a neutral truck that too little.

Something like this is what I have in mind... LINK

Hey guys, I'm going to talk about this in the "make it handle" thread. I need a day or two to figure out how to make the concept easy to understand.

[stich626]

Originally Posted by robnolimit

Stich, you are correct. Mant have tried to make a perfect spring, which would have an increasing spring rate as it compresses. Variable rate springs have not been so successfull due to the pre-load at ride hieght. With air, as you compress it at ride hieght, the effective spring rate rises, and thats a good thing. As you unload it, it becomes softer. Years ago we tried to add small tanks plummed into the bags, to act as a resivour and add to the volume of air, and reduce the change in pressure as it is compressed. It works great on a spring rate gauge, until you bring "time" into the equation. Real time testing showed that even with 1" line, by the time the pressure equalized, the bump or turn was over. Start tuning by choosing the correct bag, one that will be at 80 - 100 lbs at RH, with the bag in it's posted sweet spot. Minor corrections can be made with shim spacers, usually 1/4" alumn. and air pressure.

so ,I guess what I'm asking. is is there a wayto make shims that you can pull/add out like a spring rubber. at the track to play with the spring rate and not take all day to get in or out..
or is this going to require adjustable spring cups.. (upper and lowers) to adjust the spring rate without changing the ride height

[N2TRUX]

Originally Posted by stich626

....or is this going to require adjustable spring cups.. (upper and lowers) to adjust the spring rate without changing the ride height

It seems that an adjustable cup might be a good resolution to your concerns. If you add a threaded rod to the bottom of the cup, you could adjust it "X" amount of turns up or down to accommodate the spring rate for the track you are running.

[Navy Mechanic]

Let me know if I should start a new thread with this question.

67 SWB. Truck was lowered when I bought it and best guess is a 4/6 drop. I have air bags on the rear only and am having some issues. Got a slow leak somewhere. The culprit is probably the cheap plastic lines which come from each side and meet at the rear roll pan in a junction and fill valve. I also can't get the rear level. No matter what I do the driver's side is 3/4"-1" higher than the passenger side. Last but not least is I can only service to 30 psi max without getting an unacceptable rake angle. First time with air bags but believe psi should be higher? I know, lot's of questions...sorry.

I've seriously considered going back to springs via a cpp kit. Looking for opinion/advice on whether to stick with bags or go with springs and why one would be better than the other. Thanks.

[robnolimit]

Stitch, when I set up an air ride suspension, I build my mounts/cups/plates to about 1/2" too far apart. Then, I put in two 1/4" aluminum spacers. I like to put in a piece of allthread, maybe 1 1/2" long, and then a nut & washer for the lower bag mount. Spacers are 3 1/2" dia. aluminum, 1/4" thick, with a 1/2" wide slot to the center. Then I can add or subtract spacers without takint the lower bag mount bolt out. Just loosen the nut, let the air out, and slide in, or pull out a spacer.

[robnolimit]

Navy, Try a few things first. Seporate the two bags. Pull out the "T", and get another shrader so you can fill them seporately. Are the bags a "double bellows" type? if so they may be too stiff. I like to use a 9000 slider bag on the rear of these trucks. Once the bags are seporated, unbolt one side of the panhard rod, and put the same air pressure in each side. bounce it around and check th eheight. then adjust to get it level. If it's more than 5 lbs difference, there is another problem to find. Once it's level, bolt the panhard back in, test drive it and let us know.

[(joey)]

thanks for all the info guys.the thread is going the direction i hoped it would.anyone have pictures of adjustable cups?any suggestions on what shocks to run with bags for handling?

[Navy Mechanic]

Robnolimit-

Thanks for the advice. I'll give it a try.