Rear spring bow measurement

[David H.]

My rear springs have definately changed shape since I took them off.
The second picture will show how flat they were when still on the car with the body on. Granted, there is more weight on them at that point, however,
The first picture will show what they look like now, after cleanup and restore.
Now, they dont want to go back on the frame properly. They just dont line up correctly with the rear shackle and the front bracket mount. The rear hits the frame well before it can be connected to the shackle.
Can anyone tell me what the measurement in the second picture should be? With the spring sitting on the front bracket and the rear shackle bushing mount, what should the measurement from the bottom of the center alignment bolt to the floor be?
I know this is a tough one, but someone must be able to get me in the ballpark. How about it Joe, got any guesses?

I can compress the spring with a bottle jack and a two by four between the top of the spring and a rafter above, but how much? and will it stay compressed long enough for me to put it in the frame. I'm gonna try it. What's to loose? I've already made a big mess of the nice paint job I did on the springs!

[John H.]

Re: Rear spring bow measurement

Can anyone tell me what the measurement in the second picture should be? With the spring sitting on the front bracket and the rear shackle bushing mount, what should the measurement from the bottom of the center alignment bolt to the floor be?

David -

Per my notes from our old friend Dale Pearman, if you draw a straight line between the centers of the front and rear spring eyeholes (with the spring off the car), the drop from that line to the top surface of the spring main leaf should be 5-1/2" to 5-3/4" with the standard 4-leaf spring.

[Mike E.]

Re: Rear spring bow measurement

David--
Is it possible that you're trying to put the rear of the spring below the rear crossmember rather than above? It almost sounds like that to me; the rear goes over the top of the rear crossmember, and the shackle rotates to accomodate the different length of the spring as it flattens and arcs as you go over bumps.
Mike

[Jack H.]

Re: Rear spring bow measurement

In suspension terminology, that's called the spring's Free Arch specification...

[David H.]

Re: Rear spring bow measurement

John, thanks very much. That is the number that I was fishing for. I will be measuring it tomorrow. As you can see from the picture, it is much more than that right now.
Mike, I did try doing that way just to see what difference it might make, but no, I have it over the rear cross member. (see pic)
Jack, thanks for the correct suspension terminology. I'll try to use it in the future.