Rear Suspension Design Input Needed

bdmafia, ur right, thas how i did mine, besides, with the bags in the back and the truss that holds, very unlikely u can run the pipes that far back anyway, so, your stuck with only half an exhaust.....

 

RIDE ON BROTHER!!!!

 

Do you have pics of your setup?

 

sure don`t.......i have 3 cars with 3 differnt setup, a 2 link, a truck arm setup and a triagulated 4 like. all have their goods and bads, think my favorite is the truck arm, very simple, effective, cheap and easy......the other 2 link is gonna get changed to a truck arm the next time it comes in for some work, and the 4 link is just plain complicated and unless you are really into a ton of math and modeling very hard to do yourself and come out right, very hard to mess up the truck arm setup....

 

The Truck arm [ 2 link ] only works correctly if the axle centerline and the pivot point are at the same height. look a stock Ford Bones as an example [ or most trucks ].
When you lower the pivot point [ which is your example here ] you remove anti squat, in fact you actually adding squat to the rear end.
When the axle accelerates forward against the resistance [ the chassis front mounting point ] the wheels try to lift while pushing the body downwards, add to this some weight transfer ant the car squats down and has no traction.[ good for doing skids ]
I certainly wouldn't want to "floor it" off a corner with that type of set up, it's a recipe for instantly spinning out.

The better method would be a 3 or 4 link or a hybrid torque arm [ a-la 3rd gen Camaro pictured below ]
Keep the bottom arms parallel to the ground, then run a "Torque-Arm" or a 3rd Link up the driveshaft tunnel [ alongside the driveshaft ]
Remember these links are actually an "Imaginery centerline between 2 pivot points", so you can bent the link down under the floor and back up again at the rear crossmember [ as long as the pivot points are parallel to the ground ]
Obviously the straighter the links are, the stronger they are!

You will also need a panhard or watts link across the rear to control lateral movement.

 

all i can say, is our american stock cars can`t be too wrond, only allowed to use truck arms! and he handle very well, and my buick won`t spin the tires, hardly at all, and if you look online, you will find a company that makes them in southern california for all kinds of cars and really believes in them, because they drive the center of the car, they worked it all out...

 

and he doesn`t want to use those little short arms, they work for shit in an aribag setup when it will travel up and down 10 to 12 inches......have to have nice long arms or the pinion angle will change too much and not work very well.....

 

True! but if you look at a stock car [ or a drag car with ladder bars ] the front pivot is closer to the wheel center height.
on Drag cars this is usually on the "anti-squat line" or higher.
For a 2 link to be succesful, the arms need to be long [ and pointing to the centre to allow some bodyroll ]

The Camaro torque arm is very successful, there are now kits available to retro-fit this system on earlier Camaros
You end up with the advantages of ladder bars without compromising the roll stiffness [ plus the long bar allows for more suspension travel with minimal pinion angle change ]

 

it won`t work with theair bags, the outer short arms are too short, we`re talking about something that will have a vertical travel as much as 12 inches, and no one is arguing about the way it works or the design, you are right......wrong about it working with airbags......don`t think you are thinking about what he is trying to do...........with the airbags you have to ask the rear suspension to do things it wouldn`t normally do, which is travel up and down 12 inches and drive at any of those hieghts.....

 

Even though we are in Australia, We could never set up a vehicle like that, we require an automotive engineers compliance to do suspension modifications, as far as I am concered if you modified the rear chassis rails and set up a Tri 4 link set as per in the attached link (not including the coil overs)
http://www.mcdonaldbrosracing.com.au/tri4link.html
you could set the diff as low as you want in the chassis for normal driving and use the air bags to dump it.
We use this particular set up for any vehicle that the customer wants to retain the rear seat.

Hope this helps.

Ray

 

Ray, How long are those upper and lower arms?

 

The lower rods are 650 mm or 26" eye to eye, the uppers are relevant to the chassis width but usually 350 - 300 mm or 12 - 14" and set at approx 90 degrees separation.
The rails are made to suit the vehicle type and wheel tyre combination and a lot of guys are using the 20" x 10" units.
This particular set up has full automotive engineers approval for strength of components as well as design and function here in Oz which is mandatory.
If you were to set your suspension to be 100 mm or 4" high at the sill and when dumped to sit on the chassis when parked you are only using the bags through say 100 to 125 mm or 4 to 5" of travel, unless you go 4WD there's no need to go any higher.
Ray

 

those bags he has on the car have about 10 to 12 inches of travel.....and not really w ay of stopping at 4 to 5 inches.....so, it needs the pinion angle to be ok at all levels....and 4 to 5 inches is too low most of the time.......so, once again, the arms need to be longer.......the triagulated 4 link is excellent, but for what hes tryin to do, hes gonna have to trade his back seat for the travel he needs......or go with a truck arm kinda setup..........how many aorbag setups have the australian engineers ok`d for the street down there, that will drag the frame on the ground and lift them selves up to a driveable hieght, my guess would be none, cause its illegal here too.....

 

My question is why do you need 12" of travel, it's more to slam it than do 4 wheel driving.
Our legal ground clearance is 4" from the lowest item under the car, whats it there in the U.S.?
So if the vehicle had that 4" ground clearance for normal driving you should be OK. I would assume that the air bag system would have pressure gauges, so from being slammed to the ride position would be ??? PSI. So when raising the vehicle you would always go to that pressure.
No we can't drive the vehicle slammed, who would want to do that anyway. It can only be slammed when parked. They can be engineer approved only if a leveling system (like Air Ride) is incorporated into the system, so when the ignition is turned on the car would come up to the 4" clearance.

Ray

 

The short lower arms in a modified torque arm set up like his picture do nothing to control pinion angle, that is done completely by the torque arm, and due to its length, there is very little pinion angle change, about the same as a truck arm set up. The lower arms pivot at the rear axle, as well as the forward mount. I think this could work fine in an air bag set up.

 

Hotroddin is correct the short links set your wheel base and keep the axle square to the center line the torque arm sets the pinion angle and the ppanhard or watts link centers it side to side.
The only difficulty I see with the short arms would be lengthening the wheel base when the car is slamed or binding the drrive shaft whe all the way up

 

This is a great example of how you should due your Chevy. It's clean, simple, strong and it works well. The only thing I would change is to move the bags from on top of the axle to just in front and down onto the arms to get more travel. If you due that 10 inches of travel would be real easy. The arms on the gray frame are 30" long and are on the short side but due work without any u-joint issues but you need to make sure you have enought drive shaft yoke movement

A 3 link tork arm setup is the best of all but is also the hardest to do but can be done



oesn't?

The results are very impressive, though. This is Cinc's Chevy...



[/QUOTE]

 

Wow guys, thanks for all the input. I really appreciate it.


Now to answer some questions:

I usually drive between 4-6 inches off the ground. This is plenty for the road arround here. The only reason to have more lift is to change tires without having to unbolt the bags.

So really I theoretically could use a lower arm that is 24" long and have it bolt to the front leaf spring mount and then back to the axle.

Does the upper and lower arm mounts at the axle need to be directly over/under each other? For instance, what if the upper links pivoted 2 inches behind the axle? That would give me enough room to not have to go into the rear seat area.

I like these setups too. It doesnt put too much stress on the axle havin the arms mount inward like that?

 

we offer a 2 link air ride system with front crossmember,2 links, shocks, pan hard bar and all hardware. giv us a call @ 951 781 1268 JIMENEZ BROS CUTOMS

 

Who is Cinc? This is Chopstix ride.

 

my vote is truck arms!