U Bolt Torque Thread (Rusty Calling You)

U Bolt Torque Thread (Rusty Calling You)

I still maintain that this alleged movement does not happen, and I think I might have found proof

http://www.suspensionspecialists.com/tech0004.html

A partial quote:

"
We have emphasized U-bolt nut tightness because the center bolt area of a spring is the area of the least cross section in multi-leaf springs, hence the weakest area. If the U-bolts are loose, the center bolt area absorbs the greatest stress. When the center bolt area is clamped solidly against the axle pad, as in a vise, then the middle of the spring cannot bend and, if it cannot bend, then it also cannot break at this point. Because the middle of the spring is the place of greatest hazard, it is necessary to clamp it securely to prevent breakage at this point.
It is possible for worn or improperly fitted axle pads to be a contributing cause of center spring breakage. Since many modern springs are flat, under normal full load, pads for such springs should also be flat, and only lightly rounded at the ends."

and further:

"Wear of spring pads can only be caused by movement of the spring on the pads. If the U-bolts have been holding the spring so tightly to the pad that no movement occurs, there can be little wear."

and from here:

http://www.acespringservice.com/u-bolt.html

"
What does a U-Bolt do?

A U-bolt serves in four critical and related roles:

Primarily, the U-bolt provides the force required to clamp the leaf spring and related components firmly together. In addition to the leaf spring, these components include the top plate, axle seat, axle and bottom plate.

The properly installed U-bolt eliminates any flexing of the leaf spring in the area between the U-bolt. This is particularly critical since the hole for the centerbolt in each leaf acts as a stress concentration which would lead to rapid leaf breakage if spring flexing was not totally eliminated by the U-bolt clamping force.

By firmly clamping the spring to the axle seat the horizontal forces acting on the centerbolt are greatly reduced which in turn prevents shearing of the centerbolt.

Proper clamping of the spring by the U-bolts provides the desired spring stiffness and contributes to maintaining the vehicle ride height and handling characteristics as originally specified for the vehicle."

and further:

"

Inspect for signs of loose U-bolts

Virtually all leaf spring failures through the center hole are caused by inadequate U-bolt clamping. Also look for signs of movement within the area between the U-bolts. Worn or polished surfaces on axle seats or top plates are sure indicators that unwanted movement has occurred. Closely inspect and if necessary replace each damaged component.

and one last

http://www.performanceonline.com/blog/2009/09/top-14-spring-questions-answered/

Q: I just broke a center bolt. What happened?
A: There is only one cause of broken center bolts, and that is loose U-bolts. The center bolt is necessary to hold all the leaves together and to locate the axle in correct position. The axle is located by the center bolt head that fits into a hole in the spring seat. Then the U-bolts are used to bind the spring and axle into one unit.
The U-bolts must be tightened to the proper torque specs to eliminate any movement between the spring and the axle and between each leaf of the spring. Should the U-bolts be loose, two things can happen—broken center bolts and broken leaves.