Leaf spring question

[chicane67]

I am not sure but it is possible that my leaf springs are old and tired and are the cause of my problems

Just some thoughts..... One factor to the problem could be the OE design and the age of the steel. Is it the only problem ?? Well, I dont think so. Lets cover a few simple insights to this issue......

First, I believe you are running under-rider bars with your OE design leafs and they are showing their age ?? Well, I believe that the biggest and most appearent problem that we are looking at, is geometric. The under-rider bars, being fixed mount with solid links, move in a known and fixed geometric arch. The leaf springs however, move in an increasing radius when compressed and I bet you can guess what the problem is. Yup, the suspension goes into bind.... and that is just the beginning.



When you have the solid link underneath the spring, and as the suspension compresses, it not only drives the pinion angle positive but it also loads the leaf to the point of induceing wheel hop. The wheel hop comes from the spring being loaded into an "S" shape from the pinion angle being driven upward (due to a weak forward leaf stack) and when it reaches it mechanical limits, it unloads the spring energy and snaps back to its unloaded self. This violent state basically loads and unloads the leaf spring evertime it transitions from high traction until it reaches its limits and unloads... over and over again. This is your basic wheel hop.

HOW "WHEEL HOP" OCCURS
Rear Axle Housing Rotation Without Traction Control:

When horsepower is suddenly delivered to the differential, whether from a clutch or a torque converter, the pinion attempts to "climb" the ring gear. This sudden shock of torque causes the entire rear axle housing to rotate backwards in a counter-clockwise direction. This causes the springs to distort, resulting in severe driveshaft/U-joint misalignment.

Spring Reaction Unloads Suspension,
Causing "Wheel-Hop":

The axle housing is allowed to continue its rotation until it meets resistance from the suspension/springs, which then try to "snap" the housing back to its original position. As power continues to the differential, the housing is once again allowed to rotate back against the springs. This action/reaction of the suspension, commonly known as "wheel hop," continues much like a tug-of-war. Instead of launching your car forward, you sit there bouncing around and spinning your wheels.

A driving concept behind a link system is that you can adjust the pinion angle and locate the IC. But in a hotchkis type suspension, without a third/four (upper) link, you really dont get to control this, because the leaf suspension is dynamic. With only having a solid link on the lower and it moving in a fixed geometry, along with the leaf spring changing is arch as it is compressed, is something that is not controlled. For the linky types here, it is basically the same as having an upper bar that is too long and/or having that upper bar's forward mount too high, relative to its rear mount.

3. Now you have the rear axle centerline. (1) If "the center line of the front spring eye level with the centerline of the main spring leaf" is correct, the front spring eye needs to be at the height of the spring pads on the axle. The sping selected needs to be rated and arched such that this relationship is preserved at ride height.
4. If that doesn't give the visual stance you're looking for, or you wish to lower the center of gravity, (2) the shackles and front eye need to be moved upward. If that provides insufficient wheel travel you're potentially into major surgery.

1.) This isnt really the correct approach. To pull this off you would have to either have a very flat forward spring with no arch that it would make for an increase in rear roll stiffness so much that it would make the chassis naturally loose. Or, it will lower the ride height from having an increse in spring free arch (with the limitations being right up to the shackle going into the rear frame rail). You have to have some arch in the spring for it to have any traction.

2.) Playing around with the forward mount can be real tricky. As soon as you move the forward or rear mount, you change the RCH.