TeraFlex Lift Coil Springs overcome spring dropout by using Spring Isolators. These are built into our Front Bump Stops and Rear Spring Spacer as well as our Spring Retainer Clips. So basically, we provide two ways to skin a cat. Many believe that multi-rate and dual-rate coil springs help prevent spring "sag." This is not correct. All springs will "sag" with weight added to the Jeep, which is just compression.
We Jeepers have a terrible habit of adding weight to the Jeep. Yeah, that toolbox you added might not weigh a ton, and neither does that CB Radio or that new sub-woofer but they start to add up quickly. For this reason, we add a built-in lift to our springs to compensate for any additional equipment. For example, our 2.5" Lift Coil Springs sit at about 3 inches above stock, while our 3" Lift Coil Springs sit about 4 inches above stock, and so on. We build in this additional height so that you still get the lift you paid for after accessories.
Now, you might think to yourself, “Man I'm getting 4 inches; I'm going to have to get drive shafts.” Not necessarily. We have already accounted for the added height in our driveshaft and exhaust spacer recommendations. So yes, your lift will squat down a little after you add that bumper, but that is only because we gave you bonus height that you got used to and want it back.
While spring failure/sag does occur, it is rare. Most of the springs we bring in for testing due to reported sag tend to exceed specs, but we like those accessories and the weight it brings. I'm personally guilty of it too.