Why don’t we recommend having more than 9” of droop for most vehicles?
We have found that for most application 9” of droop is where the spring rates really fall off a cliff and start to cause the issues listed above. More than 9” of droop on most common builds does not improve off-road performance and can cause issues.
Performance is not increased because you will probably have tender coils which don’t provide any downward force on the axle. Without downward force the tire doesn’t have much traction and isn’t providing much stability.
By moving some droop travel to up travel it will provide a more comfortable ride and more balanced suspension. With more up travel the tire can absorb the bumps before hitting the bump stops. Under articulation the tire can come up higher before it starts to raise the chassis, creating a more balanced and stable vehicle.
With too much droop on solid axles it can to swing too far side to side, and the tires start getting into the body and chassis. By having more balanced up and down travel the axle will not swing as much and you may be able to achieve more travel overall.