Some observations from experience... General in nature...
*IF* you want to go 'Fast', you NEED a lot of travel really quickly.
Leaf springs are NOT the way to go.
CJs were never intended to run 100 MPH across the desert.
SOFT springs work better for trail rigs, 1 wheel will move (over a rock) while allowing the other 3 to stay in contact with the ground.
Most 'Off Road' springs are WAY too stiff.
It's WAY easier on your body, the vehicle frame/body/power units when it's not sharp beating everything.
Soft springs SUCK out loud on the highway where body roll and staying in your own lane come into play...
Again, CJs were never intended to go 100 MPH anywhere.
'Lift' is relative. You probably won't hear that anywhere else...
Straight Axles, you 'Lift' is in the side wall height of the tires you use, nothing else.
If the axle housing won't clear the obstacle, you aren't going anywhere.
Since the smallest rim you can use is 15", use a 15" rim and taller sidewall tires to increase ground/obstacle to axle housing distance, increasing ground clearance AND giving you more cushion (suspension) travel as the tire absorbs some of the obstacle impact.
They drive like
on the highway, but the spongy, soft sidewall off road tires are made for a reason...
This isn't an up armored Hummer that weighs 10 tons, soggy tires work GREAT on a light weight off roader/trail vehicle, and they give you actual GROUND CLEARANCE LIFT.
All taller "Lifted" springs supply is frame clearance for frame, and body clearance from obstacles/tires.
While you *Might* need some spring lift for body parts to clear bigger tires, a body lift gets you to the same place without the body over spring sway/roll.
The point is, if you are NOT dragging body, frame, drive train regularly,
And the tires aren't rubbing, no need to lift the rest above axle height.
The lower your center of gravity, the greater angles you can manage without tipping over or lifting wheel pressure from ground.
Before I order buggy (leaf) springs, I ALWAYS do tires first.
Find a tire that has a soggy side wall, one that's rated to be aired down so it's even more soggy (more traction AND suspension),
Since this is the only thing that gains actual ground clearance.
Once you have a tire that works well, then look into clearance.
An occasional tire rub on body or frame GETS WORSE when you have 'Lifted' springs...
It's because the spring allows the axle to move SIDEWAYS under the frame, more spring = more sway over the springs.
(This is where you start needing track bars to keep the axle centered under the frame, or a stupid stiff spring, the reason so many 'off road' springs are stupid stiff)
When you find a tire that works well, that's money in the bank.
Don't go stupid wide so it rubs, it's that simple.
Stupid wide tires work best on soft sand anyway, and not a lot of sand dune runners in the rock mountains...
The traction you NEED is directly proportional to the available power you have.
A mostly stock CJ doesn't need 15" wide contact patch on pavement, we aren't drag racing,
And if you look at high traction, low powered vehicles, like WWII Jeeps, tractors, etc. you see relatively NARROW contact patch and more agressive biting lug tires...
Take a cue from that. Wide spreads out the weight, reducing the effective 'Bite' (friction coefficient). Stupid wide requires new, non stock rims requiring more money and reducing the potential supply of replacements when you need them.
*IF* this is going to be obstacle climbing off road only,
Consider two things,
1.
Dana 44 or Dana 60 up front with outboard springs (front springs moved outside the frame on 'L' brackets,
2. Reversing the shackles, move the front axle shackles from front to back of the front springs.
Shackle reversal is a stupid effective, low budget way to increase your ability to climb over high angle obstacles.
Costs you some highway driving comfort, but most everything is a trade off...
)
