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Discussion Starter · #1 ·
after realizing that that i couldn't drop the rear of the car low enough with just cutting the leaf springs, i decided to take them out and put a triangulated 4 link. here is my question, my friend told me that its a much better ride quality when you set it up as a cantilever (instead of just putting the bags directly under the rear end) is this true, has anyone done this. here is a picture of the set up i want to put
 

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cantilever system

The biggest problem with a setup like that is that the further away from your axle that you locate your air bags, the higher the air pressure required to maintain the same spring rating of having them in the stock location, which for 99% of air bag or coil spring setups is either directly behind or directly in front of the axle. If you want to build a setup similar to that, I would recommend putting the bags either immediately behind the axle or immediately in front of it. Another problem with a setup like you have shown in the picture is lever flex, which alters your spring rate as well. The basic purpose for the links is to keep the axle in place within the chassis, and not as part of the sprung suspension.

Im curious as to why you would want to cut leaf springs. If you want to lower a vehicle with leafs, its a simple matter of just putting lowering blocks between the axle and the spring.
You didnt mention the type of vehicle you have, but I am presuming it is a car. If it were a truck, on most leaf spring jobs, the leafs run over the top of the axle vs under as in a car.
 

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Discussion Starter · #3 ·
the reason i was wondering about this system is because they told me the ride quality is a lot better. it is for my car (53 bel air) with the size tires that i want, the leaf springs will not work, besides the axle hits the frame before the car is all the way down on the ground.
 

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axle clearance

If your axle is hitting the frame now, before the car hits the ground, going to a cantilever isnt going to help any. Your axle will still require the same clearance from the frame rail. The only way around that is to either run shorter tires on the rear or notch the rear frame kick.

Remember that your car sits half the distance off the ground of your tire diameter. If you are running a 27 inch tall tire on the rear now, going to a 25 inch tall tire will lower your car 1 inch closer to the ground. Be warned that doing that will throw your speedometer off quite a bit, and will cause it to read faster than you are actually going.
 

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notching the frame

Unless you want to rebuild and completely refabricate the frame kick, thats the safest way to go. Your frame is in all likelyhood C channel. If you notch that you will effectively have only a piece of angle iron over the axle, and that wont have the strength to hold up your body. Eventually what would happen is that the body would start to warp from the frame kick back, and the more weight you put back in the trunk the sooner and worse the warpage would be. To box in the frame, you will want to get a piece of crs, the same thickness as your frame rail, usually about 1/8th inch. Once you have your notch cut, take a piece of carboard and make a template of your frame rail, at least 6 inches to either side of the notch. Cut the CRS, to match your template and weld it in to the open side of your frame rail. Then get a piece of steel tubing of the same diameter or form a strip of the CRS to conform to the notch, and weld it in as well. This will insure the structural integrity of the frame rail. IF your frame is already boxed from the factory, rather than C channel, then all that is needed is to weld in a piece formed to match your notch to replace the part of the lower side of the frame rail that you removed.

The other option would be to weld a piece of boxed steel over the top of where you plan to notch it, then remove that portion of the frame rail. The piece you weld on should pass to at least 6 inches in front of and to the rear of the notch. This may also necessitate cutting holes in your trunk floor to allow the added pieces to be installed. I would also take the piece you place over the top of the frame kick and taper both ends down at a 45 degree angle. Weld the added piece at all points where it touches the frame rail. I would also weld in a piece up into the notch to cover the ends of the frame rail left from the cut.

Welding the box tubing piece over the top then notching the frame will give you the additional clearance of the thickness of the frame rail.
 

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53LEDSLED, Max is right you're really just altering the spring rate and that setup will require a higher pressure which isn't necessarily a good thing with airbags. What do you mean by "it will ride better"? more cushy, firmer, less bottoming?

I assume you're planning on doing the notch with plates like most guys are doing these days. How deep of notch do you need on yours? I'm working on the same thing and my axle hits with about 2 inches to go before the car is as low as I want (65 Le Mans) so I'll probably need to go about 4-6 inches deeper than the frame. Do you know of any good pictures of this type of mod?

Max, Where you from in Iowa? I'm in Sioux City.

Later...


Wally
 

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Discussion Starter · #10 · (Edited)
i was planing on welding a piece of boxed steel to it. i have a pretty good idea on how the setup is going to go but i just wanted to know if this setup for the air bag would be a softer ride?

Wally, if you only need 2" to bottom out, why are you going 4-6" more? ill find some pics for you

this is my friends site, hes the one thats going to give me a hand
click here
 

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What I meant was bottom out on the frame. The axle hits the frame and I still need to go down a little more.

I measured it all out tonite and made a template. Looks like I need a 5" notch. That's assuming 4.5" of suspension compression plus a little room for a bumper.

Maybe that's overkill and I really don't need that much, I'm not sure. I still have some figuring to do. It actually works out to be no more work to make a deep notch vs a shallower one. It's an easy fit in the floorpan either way.

Thanks for the site and I'd definitely appreciate any more pics you can find.

Max,

I had to look up where Ft Madison was. I couldn't remember. We're about as far apart as you can physically be and still stay in Iowa :) I've only been down through there once on my way to Louisville. Crossed over in Keokuk.



Later...

Wally
 

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I haven't ever put airbags on a hotrod, but I fast bagged my nissan truck last year and I assume the basic concepts would be the same.

with a cantilever setup you get an insane amount of lift! I've seen 24" inches of lift and more. thats good considering 2500 and 2600 firestone bags give 7-9" of lift inflated.

I think the "better ride" concept is based on the fact that they take less P.S.I. to inflate to ride height. I have an over the axle setup w/a triangulated wishbone 4-link. With shocks it rides wonderful! alot like a caddy. But I sometimes wish I woulda done the cantilever. I can't wait until I get an older bel-air or merc to bag! good luck. PM me if you have any bag questions. that is one thing I do know. haha

www.suicidedoors.com has decent pricing.
 

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Discussion Starter · #15 ·
thats exactly the same kind of set up i going to have
and thats exactly what i wanted to hear, "rides like a Caddy" thanks for the input.

i already called cuicidedoors but they said it would be very hard on my 53
 

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Hey I am in the air bag business, and we do a lot of cantilevers. The reason people say they ride nice, is because the increased leverage softens a stiff bag. What that means exactly is that people like to use a 224c ( 2600 # ) size bag and put it on the rear. If you consider that is the bag used on the front of a fullsize truck, it make sense that that bag has way to high of a spring rate for the rear. So instead of getting a bag with the proper weight, they move the bags up on the bars. As the leverage on the bag increases, the weight it sees ( spring rate required ) is increased in direct proportion to the leverage. A set up with 2:1 leverage, needs a spring rate twice as high as a 1:1. I would look into getting a set of firestone F9000, 9001, or 9002 bags. Or possibly even air ride tech's 9100's. They will give you the same good ride, and good lift. And not require the massive lower bars needed to support the bags on the bars.

Oh... and that isn't a true cantilever. It is just a lever. A true canti has a rocker to change direction, kinda like an indy car.
 

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Well it depends on the bag. If you are going to use a bag that has to high of a spring rate, the mechanical leverage will soften the spring rate. And make it ride better. If you have the proper weight rated bag, for use mounted on the axle, then mount in on the bar, it will ride worse.
What size bag are you planning on using ?
 
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