So I tried JLUR front springs in the rear of my TJ...
Free length is 18"
compressed length is approx 4.5"-5" (9 coils x 0.5" per coil)
Ride height is about 13" and 13" is about a 5" lift. Keep in mind I have a very light TJ. No spare, no rear seat, minimalist bumper. A heavy TJ with a hardtop, rear seat, subwoofer, heavy tire carrier, and spare tire will probably sit closer to 12"
That's a little too tall for my build, so I cut an inch off of its free length. You can do this with a tangential spring end. There are several ways to end a coil spring... pigtail, box, and tangential: tangential is where the spring just stops and doesn't have any type of formed end. These can be cut. you should not cut off pigtails and square ends.
After the cut, the springs are right at 12" for ride height, 4" compressed, and 17" fully extended. Now my 12" fox RR shocks have 7.5"-8" of up travel and 4"-4.5" of down travel. I build a lower spring perch mount that the factory (JLUR) isolator fits perfectly around so the spring has a solid seat.
and the finished product...
To those who don't believe in math... I've been told that there is no way that spring is only 4" tall fully compressed... I took this picture while flexed. There is 4" between the axle pad and frame bucket (measured as close as possible to the coil. The upper and lower isolators add 0.375" - 0.5" to height and the spring still has a little left to give before all of the coils bottom out. The shock is fully compressed.
