Got a 55 Buick with Firestone bags in back, right in the same location as the original coils, lowers down great but rides like shit ! Lot of trampolining (sp?) going on. Tried playing with the air pressures, put in a set of good gas shocks still seems to have way too much bounce in back. Had to stretch the bag slightly (deflated) to reach the mounting plates when installing. Will adding a spacer cup better the ride ? Thanks Pappy
How much pressure are you running? Is the spring mounted on top of the axle? If so you only need about 30-40 lbs. to make it ride smooth. You need a good set of shocks with airsprings.
It sound to me you are running a lot of pressure to get it up high enough to drive. First off what Firestone bag are you running? This goes for what ever bag you are running. Make sure the listed ride hight is the same as the ride hight of your bag when you hve it where you are going to drive it most. Also try to get the baggs lined up a little better.
What is the Bag Diameter..5" 6" ? Reason is...thants a pretty heavy car...I think Firestone bage are too thin anyway.You may be running too small of a bag.
Running about 35 pounds to get to ride height. Bag alignment seems to be nuts on (Buick used rear coils in 55' so I was able to remove them and place the airbags in their location by adding a bag platform to the rear axle in the same spot as the coil, and used the upper coil spring mount to locate the upper bag) Used a system from MIC on the coast, Firestone 2500 bags in the rear. Diameter inflated looks to be about 6 in.Using top quality gas shocks. Almost seems to be too much air in the back, giving that bouncing effect. That is why I wondered if adding a spacer to the lower mount would compress the bag slighty at the lowered height, and require less air to get to ride height. What do you think ? Pappy
I bagged a '53 buick skylark a few months ago, and I installed firestone F9000 bags in the back, in the original coil mounts. And the 2500 bags in front. And it rode pretty nice.
[ QUOTE ] Had to stretch the bag slightly (deflated) to reach the mounting plates when installing. Will adding a spacer cup better the ride ? Thanks Pappy [/ QUOTE ] It is crucial to install the bags at the correct height, I would start by either putting in spacers or even relocating the mounts. May also need heavier shocks...
So how much different are the F9000 bags and do they maount the same as the 2500's. Also where did you get them ? Pappy
The F9000 bags are taller, and have a lower weight rating. You have to think of an air bag as a spring. And they have weight ratings just like springs. Sure they are variable, by changing the air pressure. But they are not infinately variable. You have to pick the right bag for the application. And as someone else mentioned, they also have there installed heights. The 2500 pound bags you have in the rear, have an installed height of 4.5-5" and a weight rating of 2140# @ 100 psi. The F9000 has an installed height of 9-9.5" and a rating of 1500# @ 100 psi. And it also offers about twice the lift as the 2500 bag. If you are running the 2500 in front, consider the front is usually the heavy end of the car, and you have the air bags mounted somewhat in the middle of the front control arm. So there is also mechanical leverage working against the bags. But in the rear, it is the light end, and in this case, there is no mechanical leverage, so the bags are at a 1:1 ratio. So why old you want the same bag in the rear, as you would the front ? Would you put front coils in the rear ? No. So you need to go to a lighter weight air spring in the rear, and it needs more lift, to equal out with the extra lift the front gets becasue of the mechanical advantage the control arms give.
MP48, So what your'e saying is that I have the equivalent of a heavy weight front spring in the rear, where I actually need a lighter weight spring, or bag in this case. Sounds like the added length will solve the initial install problem without having to add a spacer to the bottom mount. Now, does the F9000 mount in the same fashion as he 2500 or do i have to fab up new mounts? And, where's a good source to get these F9000 bags (read lowest price!) Thanks Pappy
Yep, you understand it exactly right. I haven't mastered picture posting here, or I would show some pics. Maybe I will try later. I get my bag stuff from www.innovativeairsuspension.com The F9000 has the same single bolt lower mounting, but has the wider 2600# bolt spacing on top. You could probably just drill a couple new holes into your existing mounts.
When you say "top quality gas shocks" just what do you mean? Unless you come back with names like KYB or Bilstein, they are not really top quality. Most aftermarket shocks like Monroe or Gabriel have low rebound dampening for coil and leaf spring supsensions. Going with shock like the Bilstein will greatly improve your ride but you aren't likely to shell out $500.00 for a set of "top quality gas shocks." Some of the aftermarket adjustable shocks are adequate at dampening airsprings but most people set them as soft as possible and leave them at that, waste of time and money. Airspring height greatly effects the ride quality. If you don't have a load vs pressure vs height chart you are shooting in the dark. If you ask the manufacturer of the airspring they should be able to provide you with one. The 2500 pound bag, 6.4" in diameter lists out like this using the information you provided: 6" loaded (ride) height at 40psi will give you 566lb force at 309 lbs/in spring rate. That means you are carring 1132 pounds above the rear axle. that sounds about right. What doesn't sound good is the spring rate. Stock is about 120 lbs/in spring rate, so I would say what you are experiencing is an over sprung condition. If you really want this thing to ride nice I would suggest converting to a tapered sleeve bag like th 110/70 series bag (I belive the 9000 bag mentioned earlier is one of these type). These bags will maintain the load rating at the same air pressure but drop your spring rate down in half. That puts you right where it was stock! Your quality gas shocks won't be overworked either!
Without sounding like a DICK,....Ditch the Firestone bags and go with "Slam Specialties" bags.The come in size ranges from 5 to 9 inch diam.You can get pressure ranges from 180 to 1200 psi ranges.Plus they have a Double wall which helps Eliminate the "Trampoline" effect.I have heard Nothing But Bad about Firestone bags.And also what the others said...Get better shocks...Just make sure that they Will Not Top or Bottom out....i had to put a Rancho RS 5000 shock on my Buick, A 4W drive application. Just my $.02 Check these guys out www.fbimini.com
Please explain this, because it makes it makes as much sense as bacon flavored icecream...... [ QUOTE ] Plus they have a Double wall which helps Eliminate the "Trampoline" effect. [/ QUOTE ] I have only heard bad things about Firestone from guys who improperly install their product or abused it from overloading or too much air pressure for the job. Now if your goal is to hop a car like a lowrider competition I could see a need for double wall this and that but otherwise it just adds to wall stiffness and increaces spring rate. Just the opposite of what this guy needs, and by the sounds of it the exact reason you needed to put 4X4 shocks on your car!
I used Firestone first off.I did not like them because they had too much "Bounce"I dont by any means "Hop" my car like a "Lowrider"Thats Not what Im trying to say.I just think that the Stiffer bag Offers a Better ride for heavier car.Thats all.I only used the 4X shock because the bags I installed Turned out with a 11 inch travel from Bottom to top.And That is NOT overexpantion.Im sorry for the Confusion and I hope this will help clear it up.
Hmmm, just wondering because in the airbag control post put up by Empire you stated you used compressed nitrogen to inflate your airspring system and it wasn't fast enough for you. And by the bragging about getting 11 inches of travel I can tell that is very important to you, not necessarily ride quality. I am happy for you because you found your ZEN place in the world. A 55-56 Buick is indeed a fairly heavy car compared to a mini-truck but I have the spring books and charts that tell me how heavy a car is and how much spring rate the original designers specified for the apropriate ride quality. Over the rear axle the Buick weighs 1100 pounds of sprung wieght and requires 120 lbs/in of spring pressure. The entire car is very close to 4000 lbs total, not any heavyier than a modern mid-sized car today. IN this particular case the guy is complaining about a ride that is too stiff, oversprung, but in his own words. [ QUOTE ] Lot of trampolining (sp?) going on. [/ QUOTE ] Adding a "stiffer" bag is only going to make the situation worse. Adding a stiffer (read: more heavily dampened) shock absorber will cure the effect stated but add to increased ride harshness. Most people are convinced through clever advertising that an air spring suspesion is a cure all for bad driveability charicteristics, riding on air! In reality modern OEM type air spring systems are far more complicated than what we use in hotrodding today and still suffer from inherent design flaws, but the public wants them anyway. Audi, Mercedes, Lexus etc offer true active and semi-active hydraulic systems that have been proven to be better performers in real world situations but they are far less popular than the air spring systems. All of which are far more complicated and less reliable than good old coil springs and conventional dampers. Of course no one is willing to leave that stuff alone. Check these out: Delphi Magneride Bose Suspension systems Mercedes Active Body Control Liquid Spring Technology <<< this is cool stuff right here I myself am convinced that the Ford Explorer/Firestone flap a few years back was accelerated by the use of an air spring system on those trucks. And as I stated earlier because of the low frequency nature of the air spring over a coil or leaf (or active suspension) the suspension was not capable of keeping the wheels on the ground and causing the driver to lose control and thus, roll. Have fun!
I was just trying to help by stating my opinion..You're obviously Much more Knowledgeable in this Field than I.I respect your Knowledge.Again.I was just trying to help.
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