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Old 07-31-2017, 05:43 AM   #1
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Default Is my crazy idea good or bad?

I am copying this from my project thread, I just wanted to get more eyes on it here.

I have a crazy idea for my SAS suspension and I want to get more opinions on it. My plan is to use a half of a leaf spring on each side to locate the axle but use coil springs to support the truck.

Like this.


So think of the half leafs like a Ford radius rod, or the arms on a LandCrusher. But since they flex a little they wont bind as easily.
I think it will react acceleration and braking forces fine because a normal leaf setup is only anchored on one end. Since I'll have cross over steering I plan to use a panhard bar, so the leafs wont have to react side loads.

I know it's crazy, but is it stupid?

Thanks for looking.
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Old 07-31-2017, 02:12 PM   #2
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You want the arms that control the axle to be rigid. Leafs flex. If you go through the effort of mounting the let's you might as well go all leaf or make it a 3 or 4 link system. A few guys here have done SAS and I hope they will chime in.
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Old 07-31-2017, 03:40 PM   #3
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I've seen people cut the leaf springs in half just behind the axle and use either a coil over or a coil for the suspension, so it's not a crazy idea.

I think you would be better using a rod with a swivel type end on it to allow for more flex, the leaf spring in the stock hanger will only allow for up and down movement and may limit suspension travel.
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Old 07-31-2017, 03:59 PM   #4
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Not a good design - even replacing the leafs with tube your still working with a 2 link but looking for massive travel.

Your basically going to have a shit ton of pinion change and a suspension arc that carries the axle several inches forward/back.
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Old 07-31-2017, 04:03 PM   #5
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not a good design because nothing will control the side to side motion of he axle. the leaf spring mounts would be in bending like a bitch. theres a reason the leaf springs are mounted at both ends.
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Old 07-31-2017, 04:21 PM   #6
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If you plan to drive the thing on the road that's a poor idea, you'll have control issues and crazy death wobble at highway speeds.
The stock leaf spring locations are not the same locations you'd use if you were doing a link suspension, they will still bind as the suspension flexes up and down.
The shackle combined with the rubber bushing in the leaf is what allows articulation as the tire travels up and down, by removing the shackle you're removing a lot of articulation.

Link suspensions in stock form also use rubber bushings but anybody who takes a jeep 4-wheeling soon upgrades to a creeper joint/johnny joint type control arm in order to stop the arms from binding in the suspension.

You'll also have a very hard time finding any research on this topic because it's not really covered, if this is your first SAS i'd recommend going over to pirate4x4.com and searching through some threads.
Also , what type of sas are you planning, what tire size are you looking to run and what type of wheeling will you be doing?
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Old 07-31-2017, 04:28 PM   #7
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it really sounds like you are trying to avoid a 4-link. why exactly do you want coil springs over leafs for a sas swap? is it to increase overall travel?

also i presume another reason for this idea is space for mounting the leaf spring?

what about some crazy ass transverse leaf spring like the rear of a corvette? it could mount to either side of the frame, low side down like a U-shape and attach to the center of the solid axle. would clear the pumpkin and control side to side or lateral motion of the axle. you could then use a radius arm and maybe youd need a longer one from a 2wd, to control longitudinal motion. theyd have to be beefier than the stock mounts as the a-arms up front carry most of the loading.
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Old 08-05-2017, 03:09 PM   #8
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Thanks for all your comments. I think I'll go with plain old leaf springs.
The reason I didn't want to use them is they seem to ride pretty hard, but I think that's cause I've only ever driven old trucks with stiff springs. With the right springs and shocks I should be able to keep a nice smooth ride.
Does anyone know a formula for choosing spring rate based on vehicle weight and wheel travel?
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Old 08-05-2017, 03:27 PM   #9
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Are you wanting up travel or down travel? My unedumacated understanding of it would tell me a soft leaf would give nice up travel and your shackles will be more important in down travel.

Syn and Res both run SAS currently. I know a few others here have too.
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Old 08-05-2017, 08:41 PM   #10
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Check out Bonney motorsports on Facebook, Jared is really well informed on what leaf packs work best and I know he sells custom leafs for nissan sas setups.
Personally I run 57" Ford leafs and they flex really well, however my rear shocks have way too much valving and make the ride fairly stiff. There is a formula for comfort though.
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