Spring Rate - Spring Load - Load Rate From Eaton Detroit Spring, Inc
The Only Way to Measure Leaf Springs From Eaton Detroit Springs(or skip all this and go right to the Measuring Form)  
Blocks.... to use or not to use...          by Eaton Detroit  Springs
Mono-Leaf vs. Multi-Leaf Springs From Eaton Detroit Springs, Inc
LEAF SPRING SUSPENSION Control arms are not required on leaf spring suspensions. The leaf spring is connected to the axle housing with U-bolts and to the frame by bolts in the front and by a shackle assembly in the rear. The shackle assembly allows spring movement.
TORSION BAR SUSPENSION What: There are no coil springs in a torsion bar suspension system. Instead, a torsion bar supports the vehicle weight and absorbs the road shocks. While a coil spring performs these functions by compressing, the torsion bar acts by twisting.
COIL SPRING SUSPENSION On a coil spring suspension, the spring is mounted between the axle housing and frame. A lower control arm connects the axle housing to the frame. Some vehicles use an upper control arm for added stability.
The following is excerpted from “Spring Tech 101” an 8-page fully-illustrated downloadable PDF booklet available from Eaton Detroit Spring at www.eatonsprings.com.