Here goes.. I'll try and keep to the topic, sorry if I start rambling.
Roll stiffness (along with a higher COG in the back than in the front) is why the rear rolls more than the front atm.
If you design an effective link design, the roll stiffness will drop even more, as there will be no bushing bind fighting the articulation.
Imagine a single coil spring in the centre of the rear axle. If there was no bind in the link design, this would have no roll stiffness. If you drew a line from the tyres contact patch to the COG of the rear of the car, and inclined your springs along that line, your roll stiffness would be as high as possible for that spring rate (assuming no bushing bind)
With the rear of the coiler, there is a funny situation where the springs are well inboard (lowering the roll stiffness) but the design re introduces (some) roll stiffness by fighting articulation.
The problem is that the springs are way outboard on the front of a coiler, and the COG is lower in the front than in the rear. Add the stock front swaybar and the front and back are hopelessly mismatched.
This does not really present itself as a problem how suzuki design the car, for 29's, no lockers, no lift etc, with no real intention of hard off road use.
I think you are on the right track with a tunable swaybar, but I think once you get it to feel right on the road, you won't disconnect it off road. US experience indicates that if you get swaybar tuning right, they are not an impediment to articulation. The idea will be to get to balanced roll stiffness front to rear, or slightly lower roll stiffness in the front than the rear.
(here I go with a ramble) I believe that if a car has poor on road behavour, it will have bad offroad behaviour too. Everything my G does badly on road it does badly off road too. Think about cornering g's. A 4wd driven swiftly might build .3g lateral force. If my dodgy assumptions are right, that equals about 27odd degrees of side angle. If your car is wobbly or behaves badly on a fast corner on road, then it will feel bad whan placed under the same forces off road, which is not hard.
You spring ideas depend a bit on spring design and where you bumpstop the car. Not all 3" lift springs are 3" longer free length. This is because they have a higher rate too. some "lift" springs are actually shorter than stock springs because the lift is done with higher rate only.
Theoretically, if you are happy with the stock rear spring rate, you could move the top mount down 2", fit new internal bumpstops that are also 2" longer, have "stock" vertical travel and pick up heaps of articulation over what you have now.
The sierra problem is getting along enough spring in there with a low enough rate. sierra rear coils are quite small diameter, I know that you can buy coilover springs at very low rates at up to 14" free length. These are ground flush top and bottom and might be of some use.
With heavily inboard springs like a coiler, you really need to treat articulation and travel separately. You only need enough travel for the speed that you want to move at, but by shock location and bumpstopping, you will be able to get very high articulation.
Re the top hat coils, I don't think they will work usefully at all if the top hat coil has a higher rate than the road spring. a sierra will not have enough tyre, wheel and axle weight to compress them, and ther won't be enough leverage to make it much use.
depending on how you set up the in-coil bumpstops, it might be possible to use a urethane sleeve from a coil over and a tender spring between the top coil mount and the road spring. This is a good way to reduce you effectove spring rate too, as the rate of the road spring and the rate of the tender spring work to negate each other. I think this would be a better solution than the top hat coil idea on a car without 44's, rockwells etc to pull them down.
Lockers: Yeah, IMHO without lockers, you can never get a car far enough into an obstacle, or build enough traction, to generate really bad suspension behavior. My G could never get into a big enough angle without the lockers on to make it misbehave. a rear locker only is almost worse, as the front cant pull the nose down, so the rear just digs in and pushes the nose higher.
It (might) be possible to set up the links on a 4 link to allow, say, 75 degress of travel, but your car would roll with the tyres still on the ground. To allow this, though, the springs would have to be about 7 ft long and the shocks 12 foot long
I don't think we will see airshocks over about 16" of shaft travel on comp cars, and bear in mind that these cars tend to run the airshocks very close to the wheels and very close to the cars roll centre. Therefore, my idea is that the advantage of a four link is the very precise control of geometry (antisquat, roll steer, caster/pinion angle) and the ability to ditch a panhard rod, also, the ability to remove bind from the effect of calculating spring and shock rates.
Double bushed radius arms are terrible for articulation, and the more you artiulcate them the higher their roll stiffness goes. I think that with a coil sierra as an example, shock and coil lengths acutually depend on this a bit to give "acceptable" road ride and control body roll.
If you want to run stock spring rates, I like the idea of getting special springs wound. Thinking out loud, maybe shoot for about 4" over stock length and set the coils 2" higher than stock in the chassis for your 2" of lift, with stock bumpstop clearances (? just an idea) I think you would find that most coil lift springs would be 20-30% stiffer than stock. not helpful for travel.
I don't think you will have the same rates front to rear. with exactly the same suspension suspension design front and rear in the G, and only lightly laden, I run 146 lb/inch in the front and 230lb/inch in the rear and the rear is too soft. I would get stock coils "rated" by a suspension shop that does race car stuff and go from there. I think you might want to go up about 10% to help prevent bottoming when you need to use a bit of momentum without having to go too stiff with the shocks.
for the front, you would want to keep the panhard, or the bumpsteer will get out of hand. My plan for Paul (club members) car was to run an extra link on top of the axle on the passenger side (minor exhaust mods) this would remove all bushing bind ( with new lower links, one bush at each end only) and allow caster to be easily adjusted. This will drop the roll stiffness and allow the front to be worked out as per the rear- without the bind. Josh Browne who used to work for GT suspension in Melbourne built the "sidewinder" 80 series with this set up in about 1994. This car was enormously impressive- about 5 feet of articulation was unheard of in the day, and amazing balance.
I actually think that this mod alone would transform a coiler, without touching the rear. ( I know you have to do your rear due to breakage) Mostly because of its effect on balance.
Balance is my pet love
Sorry for the ramble, I hope this gives you some stuff to ponder.
Steve.
