Leaf spring buckling upward

[rww124]

Hi. I was wondering if anyone knew why when a car is lifted off the ground on a hoist thus removing any weight on the tires why a leaf spring would buckle upward toward the underbody of the car which then causes the rear shackle to pull forward and jam against the frame where then you have to take a prybar to lever/force the spring back down to put the shackle to it's correct position of leaning slightly toward the front of the car. I have 3800 pound Super Stock springs in my 1969 Super Bee that were added by the previous owner. This problem is only occurring on the passenger leaf spring. Thank you.

If your only contribution to this question is a blunt "just replace the springs" please do not respond as you are not proving any answers to my question.

 

[dadsbee]

It's all in the geometry.

Did you not ask this exact question a month or so ago and everyone went through the motions to help? If it wasn't you, someone else did...

 

[RemCharger]

Hi. I was wondering if anyone knew why when a car is lifted off the ground on a hoist thus removing any weight on the tires why a leaf spring would buckle upward toward the underbody of the car which then causes the rear shackle to pull forward and jam against the frame where then you have to take a prybar to lever/force the spring back down to put the shackle to it's correct position of leaning slightly toward the front of the car. I have 3800 pound Super Stock springs in my 1969 Super Bee that were added by the previous owner. This problem is only occurring on the passenger leaf spring. Thank you.

If your only contribution to this question is a blunt "just replace the springs" please do not respond as you are not proving any answers to my question.

The answer is the spring has too much arch.
On the S/S springs, the pass side is arched more.

 

[RemCharger]

It's all in the geometry.

Did you not ask this exact question a month or so ago and everyone went through the motions to help? If it wasn't you, someone else did...

Yes 4 pages of answers.
The spring is too curly. If that helps.
Leaf springs

 

[Dave6T4]

I have 3800 lb. SS springs under both my cars. If you look at your passenger side spring, you will notice that the leaf directly under the main leaf stops well short of the rear spring shackle. Compare it to the driver side spring where this underleaf extends almost to the rear shackle, giving much more support in this area. On my cars, I found that this area was actually buckling downward without this support. I noticed this problem on friend's heavier B-bodies as well. Our remedy was to replace the weaker passenger side spring with another driver side one. Problem solved.
Does your car have the proper two-inch longer front spring hangers? This makes up for the 2" shorter front segment of the SS springs (actual A-body springs), to position rear axle properly. Dodge used 2" longer hanger; Plymouth used 1" longer. Dodge had 117" wheelbase, and Plymouth had 116" . Both cars had identical understructure, and the wheelbase difference was made up by these front spring hangers. I just measured the front hanger on my 1967 Coronet R/T equipped with 3800 lb. SS springs, and correct Mopar Performance front hangers. The distance from body structure where the hanger attaches, to the spring eye-bolt is 5 1/4" . Anything different than this is wrong. I hope this helps.

 

[beanhead]

Hi. I was wondering if anyone knew why when a car is lifted off the ground on a hoist thus removing any weight on the tires why a leaf spring would buckle upward toward the underbody of the car which then causes the rear shackle to pull forward and jam against the frame where then you have to take a prybar to lever/force the spring back down to put the shackle to it's correct position of leaning slightly toward the front of the car. I have 3800 pound Super Stock springs in my 1969 Super Bee that were added by the previous owner. This problem is only occurring on the passenger leaf spring. Thank you.

If your only contribution to this question is a blunt "just replace the springs" please do not respond as you are not proving any answers to my question.

If proper hangars are in place, it's just something that happens with worn out or shitty springs or springs with too much arch (even new ones can be shitty). You've already figured out to pop the shackle back in place with a prybar (I used to keep a big screwdriver in the trunk, just for that purpose!)
Beyond that if you're looking for a detailed scientific explanation, maybe you can contact a spring manufacturer to see what they have to say?

 

[Dave6T4]

This has happened to me too. Lots of times, when the weight is off the suspension, the rear shackle is pointed straight up/down. When the weight of the car comes back down, then it is 50/50 whether the shackle kicks back or ahead.

 

[toolmanmike]

 

[ornaryal]

a few years ago i bought a new set of springs for wifes 55 belair from speed shop fought like hell to get them in they pulled the shackels way in too far . so i phoned detroit spring , that made them , checked the numbers and they were over arced , for a gasser . could not use main leaf . used the rest with org main and 20 yrs later still sits good , for my b bodies in past have used pu leafs under org main leaf .

 

[toolmanmike]

It's all about the arch of the spring. It inverts the shackle. Normal? Not really but it will happen. Both springs did what the OP described when I replaced them. A long pry bar between the spring eye and the shackle fixed the issue.

 

[RemCharger]

If the OP likes how it sits, then be happy.

 

[dadsbee]

As I noted in post #2, why are we doing this again.. so soon?

 

[rww124]

If proper hangars are in place, it's just something that happens with worn out or shitty springs or springs with too much arch (even new ones can be shitty). You've already figured out to pop the shackle back in place with a prybar (I used to keep a big screwdriver in the trunk, just for that purpose!)
Beyond that if you're looking for a detailed scientific explanation, maybe you can contact a spring manufacturer to see what they have to say?

I do have the longer hangers intended for the shorter Super Stock springs. The information you provided at the least is that this can be a somewhat common occurrence on some cars so no scientific explanation is necessary. I purchased the car with the springs already installed so do not know their history. If new springs can be shitty and do this then perhaps the previous owner got a bad set or they cheeped out on less expensive springs. As far a a solution goes a prybar was used a couple of times however I was concerned about scratching up the car so my Cousin came up with a solution of installing dense rubber blocks on top of the leaf just below the shackle so the shackle can no longer move far enough forward to jam up against the frame. Thank you, your information lets me know that my situation is not an isolated one.

 

[rww124]

The answer is the spring has too much arch.
On the S/S springs, the pass side is arched more.

If the passenger side leaf is arched to the point of flipping forward enough to jam against the frame wouldn't the manufacturer make changes to the arch through complaints from customers or does the passenger leaf have to have more arch when a car is launched resulting in weight transfer to the rear passenger side of the car.

 

[rww124]

It's all in the geometry.

Did you not ask this exact question a month or so ago and everyone went through the motions to help? If it wasn't you, someone else did...

I may have been me as there was so much **** that was done wrong when the car was built it's got me stressed and running in circles.

 

[dadsbee]

I may have been me as there was so much **** that was done wrong when the car was built it's got me stressed and running in circles.

No, it was you! Remcharger was nice enough to put the link to your thread in post #4.

 

[rww124]

No, it was you! Remcharger was nice enough to put the link to your thread in post #4.

Why ask and answer?

 

[65hemi]

My 3600# SS spring at full extension. The hanger swings back into the proper position when the car is lowered. My car is rarely at full extension except when I take the wheels off.

 

[Dave6T4]

Why ask and answer?

I think what @dadsbee is getting at, is that forum members took time to volunteer help and suggestions, apparently 4 pages worth. Now you are back asking the same question. Really, most of us are quite willing to share our experience and knowledge with those following in our footsteps. At the same time, we like to know that we are being listened to.
I once worked with a guy who would ask for my help, and I would give him the best answer I could. Then, he would go and ask a couple of other nearby guys the same question. I found it infuriating.