I emailed Steve Szymanski (Industrial Ch***is in Phoenix) about how to calculate airbags for my 1964 Olds Starfire. I got more, but very useful information, than I expected. Had to open my brain back up and get out the thinking cap. As an example, my car is 4400 lbs. Here is his reply: Figure about a 60/40 weight split on your car. That would put 2,640 pounds or so on the front wheels. You could do some math and figure out just how much load is on each spring (air spring) but it's close enough to ***ume each spring is 50% of the distance from the wheel to the control arm bushings, where they attach to the frame. This is kind of a round about way of saying each spring carries the full weight of the car, or together they carry double. It's not really that simple for for the terms of air springs it's close enough. An air spring rated at 2600 pounds each would be sufficient. Check out the Firestone website http://www.firestoneindustrial.com/...ides/airmount/sgairmount_doubl_conv_imp.shtml , check out the chart on the bottom right corner where they pose force in lbs to air pressure and loaded height. http://www.firestoneindustrial.com/pdfs/industrial/datasheets/IMPERIAL_PDF/EMDG_20-2.pdf This one would be 7" tall at ride height and 60 PSI to hold 2590 pounds. And the spring rate would be 534 lb/in. which is kind of stiff but workable. If you watch the tables on load vs air pressure you may be able to dial in the correct parts and set up. Typically if you can achieve ride height with a lower installed height like 6" you can use lower air pressures to hold the weight and have a lower spring rate. This is where the large chart on the right helps, eg. 6" high at 55 psi would hold 2600 pounds (estimated). Stock spring rate was probably around 350 lb/in but kind of soft so an increase in spring rate coupled with a high quality performance shock may be just what you are looking for. Nitrogen tanks are usually for playing with your system. You can use it as a primary source for air but your supply is limited and when you run out and don't have a back up system, you're screwed. Most guys use the nitrogen tanks as a secondary system shut off with a ball valve or some type of shut off. If you do run dual systems, put a check valve on your regular low pressure tank to keep the nitrogen from blowing it up. Steve Hopefully this will help others' decide what bags may be best for your vehicle or at least understand whats going on.
If you read between the lines here, there is information on how to tune an already existing system. By changing the height of the air spring at your desired ride height you can push the spring rate up or down depending on needs.
I have some technical sheets on the Slam specialties bags I will post up once I get them scaned in later tonite.
That would be great info to have. Slam Specialties only quotes what their product is equivalent to, not actual numbers.
??? When I go to the Slam Specialties website, go to compare, it's got all the numbers there. Then if you go click on Air Bags, it says click on the model and it downloads a pdf that has dimensions.
slam specialties bags are the way to ..the way they are designed they take way less PSI to lift compared to a firestone, conti-tech, or air lift brand because slam specialties bags dont expand out like a baloon they only lift all the other bags expand out before going up theres plenty of other reasons to go with slam but thats the main thing about em that i like.. been using em for years never had any problems with em other than normal wear n tear... and they are a local company
Dimensions, yes. Load and spring rates vs air volume and pressure, not so much. I'm more concerned about the math involved and how it is going to perfomr over whether or not it fits the situation.
http://www.slamspecialties.com/compare.html If these perform the same in lb/in as they compare to the other springs then this is a no brainer. But I would like to see something other than max load and how much PSI you can put to them. I'm not interested in hopping or playing, my customer demands that I make the car/truck actually ride well. Example: http://www.slamspecialties.com/air_springs/RE-7.pdf No where on this chart does it tell me what the spring rate is for this spring with say 80 psi and an installed height at 7" and how much force it exerts. The Firestone charts do.
iv never seen any thing like that with the force on the chart.. but for example in a s10 pickup with a firestone 2500 air bag it takes around 140psi to get it to start lifting the truck with a slam re6 bag it takes about 100-110psi to start lifting the truck... dont know any technical stuff on the bags i just know slam specialties is a better product... i know this site isnt about mini trucks & all that i just threw it out there as an example
yea it is... its a huge differance in ride quality too.. its cause the slams dont baloon.. a 7" slam never expands out only up so no psi is wasted.. in my head if it starts lifting the car at 150 psi or 110 psi the force is the same??? its just not wasting the psi pushing outward balooning the bag..
Uh, yeah I read that on their page. It has more to do with the volume of air. A larger volume of air in a smaller space will exert more force but at a higher frequency. The same force spread over a larger area will do more work, it would be real interesting to see side by side numbers at similar load ratings as well as the frequency to determine if the spring rate is higher or lower. They sure seem stiff by the ratings given to fully compress them.
yea the re models are the cheepest ones they make and even they they are pretty hard to compress then theres the rs & es i think somethin like that... iv always used the re7s on most of my projects
Sorry I did not get those charts up last night.. Scanner bit it. I am getting a new one today and will try again tonite.
Slams are the ONLY bags that do not Balloon! Airbagit has a Slam copy that they claim does not balloon out but it still does, just not as much as others. Firestones and conti's are good bags for what they were originally designed for and thats .... Big Rig suspensions. Slam bags are the better ones for getting the ride quality at any given ride height because their spring rates are better. A.R.T has managed to get a good ride out of their products through engineering, thats why you have to get all of thier stuff and thats why its so expensive.
Didnt see this post before, the sheets I have list the spring rates and PSI lift capacity for the bags at 10PSI intervals and the amount of lift you achieve. for example (not 100% accurate but an example) a RE-7 bag would lift 1400 lbs 10 inches at 100PSI. Again that is not accurate but thats kinda how the chart lists it and I dont have the actuall chart in front of me right now.
LOL, do you work for these guys? You sound like an infomercial Does the chart you have list any lb/in rates or frequencies? Load per height and psi are useful, without a lb/in rating it is nearly impossible to judge ride quality and shock valving.
That's an especially huge difference at those specific pressures when you consider which pressure switches guys run. Use a 150 psi pressure switch and you can't even get the truck in the air until the tank is completely full.
In common guy terms (my terms), you should take the time at initial instal to put the largest bag possible. It will take less PSI to lift and ride a lot better with less PSI. I am about to bag my 66 Starfire, I am going to use 2800lb bags because of the weight of the car and the big block. I am going to cut most of the spring pocket out and reinforce it with some 10-12 in pipe cut in half. It will look similar to the ch***is tech spring pocket eliminator kit.
No I dont work "for" Slam, I just sell Air Bag components and strongly reccommend Slams because thats the only bags I would ever use. You will have to see what the charts show tonite. I am away from the shop till 3pm est.
Jimminy Christmas that's a ton of pressure! The most air pressure I have ever needed to achieve ride height on my installs was 80 psi. Most of them would hit the upper stops at 100-110 psi. Sounds as if you could use a bit of re-engineering on that setup.
on my 50 dodge u used re7s in the front & re8s in the rear 7 is a tight fit in the front of he dodge suspension but it works out great cause the bag dosent baloon
HOORAY! How many more times are we going to hear this. You guys made the point, what it has to do with the function is beyond my reasoning. It's not as if this is some huge problem in any of the systems I have ever repaired or installed.
As promised here are the charts on the Slam Bags. Sorry but I lost the one for the RE-7 but here is the RE-6, RE-8 and the HE-6 and HE-7. If they are hard to read or if someone wants a better copy just PM me an email address and I will email you a copy.
I had a full size 05 Chevy silverado with slam bags and my ride hieght was at 95 psi in the front and 60 in the rear. Never had a problem with them, I had Firestone bags on the truck at first but then quickly took them off cause I popped 2 bags and bounced around a lot. Never popped a slam bag didn't bounce around and drove from Virginia to California with them and had them on the truck for 4 years until i sold it
That looks like the same info they have on the website. Thank you for your effort, but the information on frequency and lb/in of spring rate is still missing. I am guessing they don't know, otherwise they would have made this information available.
hmmm, well, what if you tried to calculate the spring rate like a traditional spring from the figures on that chart? It would be nice if Slam Specialties could provide volume figures. Air springs are a progressive spring, so the rate would be inch-for-inch for a particular pressure, because the pressure changes are the volume (deflection) changes. The trouble is it will not be totally accurate because it isnt very likely you can judge the second inch of deflection as the same pressure as your start pressure. Follow me? I'm sure you gain some where around 10psi with an inch or two of deflection but without the proper figures you can't be sure. If you could know for certain the load it takes to compress the spring each inch, you just need to figure it like a combination spring or progressive spring. (Spring Rate of first inch of deflection x Spring rate of second inch of deflection) ÷ (Spring Rate of first inch +Spring Rate of second inch) and that would give you your figure. Too bad they don't have that kinda info available. Has anyone tried to contact the company?
The Jalopy Journal
