here's how i think about it,
1. when the torque of your engine drives the rear driveshaft(pinion gear) to rotate the (ring gear)axle shafts and tires, there is an opposite reaction, (this is the one that pushes the front wheels in the air when a dragster takes off [img]/wwwthreads_images/icons/smile.gif[/img])
so when the tires are rotated one way, the axle housing wants to rotate the other way.
2. the arch of leaf springs gets flatter as more weight is loaded on, and when the axle housing tries to rotate the spring are forced to take a kind of laying down "S" shape. this is "Spring Wrap"
the problems that happen with too much spring wrap or many, the biggest is "Wheel Hop" this occures when your springs wind up (like and "S") and release again and again, this caused your rearend to bounce. (which can cause all kinds of different breakage)[img]/wwwthreads_images/icons/smile.gif[/img]
so, this affects all leaf spring axles.
very stiff springs can control this (but are not very flexible)
low engine torque and axles with highway gears (2.73/3.07etc..) don't have the mechanical leverage to cause many problems. (not a great wheeling setup)
softer/flexible leaf springs can be wound-up easier along with super low gears possibly creating an overpowering mechanical advantage.
also spacing the axle housing farther away from the springs (like when using lift blocks on a spring over setup) creates an even bigger leverage to make more spring wrap.
so basically i think going from a SUA to a SOA creates more mechanical advantages that may cause noticable axle wrap/wheel hop.
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