How to test leaf springs for tension?

[Sarikatime]

The springs on my 12 are weak and soft. Is there a test as to how much weight should depress the spring and how far down for proper tension to be like when it was new.
This is a rear tapered spring but the front is even worse. Frank

[TRDxB2]

There are machines to test and re-arch the springs. I couldn't find any load specifications so..
You could take it apart and measure the height of the arch and that might confirm something.

These are dimensions for a 7 leaf Front Spring (1920-'25). Y
Measured Length and Height of each leaf lying on flat surface.
9-3/4" -- 3/4"
13-7/16" -- 1-1/8"
17-7/8" -- 1-5/8"
22-5/8" -- 2-7/16"
27-3/16" -- 3-1/8"
32-1/2" -- 3-7/8"
33-1/4" -- 4-11/16"

8 leaf (late: 1926-27)
Length of Spring Leaf //Overall Height of Leaf
8-13/16" // 9/16"
11-9/16" // 13/16"
14-13/16" // 1-1/8"
18-5/8"// 1-7/16"
22-5/8" // 1-7/8"
27-1/8" // 2-1/4"
31-5/8" // 2-11/16"
33" // 3-5/16"

9 leaf (late: 1926-27)
Length of Spring Leaf // Overall Height of Leaf
8-3/4" // 1/2"
11-1/16"// 3/4"
13-1/2"// 15/16"
15-13/16" // 1-3/16"
18-9/16"// 1-7/16"
22-5/8" // 1-15/16"
27-1/8"// 2-5/16"
31-9/16"// 2-11/16"
33" // 3-1/4"

[mbowen]

Frank, are the “lengths” of the springs measured along the arc or straight across the chord line? Just curious.

[pron022020]

For what it is worth as someone who has been thru several different cars and leaf spring problems, it seems that leaf springs can only flex so many times until they flatten out. I have tried having shops rearch them hot and cold and they both eventually flatten back out. I think a new front spring is almost always a necessity. The rears usually don't wear out because of the weight distribution of the car and roughness on the front end.

[TRDxB2]

Frank, are the “lengths” of the springs measured along the arc or straight across the chord line? Just curious.

I re-checked each of the references, all of which were member measured in past discussions, so unofficial
For the 1909-1915 seven leaf it was stated that the measurement was "measuring in a straight line from outside to outside". No indication if the spring was detached from the vehicle or taken apart. But I would think that it was done with this spring still put together.
--
The other measures (20-25 & 26-27) indicated that each spring was measured with each leaf laying flat.
So some assumptions need to be made about those measurements
-I'm thinking that "laying flat" means "on edge" versus "upright" on each end.
-The the standard way to measure the main spring is measured straight across (chord line) from the center of one eye to the center of the other eye. So I think this was done to compare with suppliers replacements.
-Its reasonable then to assume that the remaining leaves were measured the same way - chord line

It would be great if someone could find an official reference with an unambiguous description of how it was measured

[Sarikatime]

Tyler, as per your recommendation I fully agree and have ordered new front springs. The one on the car hit the axle when I stopped in a hurry. As Frank stated in both his posts, the rear is a little less problematic. This is a very heavy all wood body towncar and it only had 7 leaves and some in the order of smaller to larger were missing. While driving when I turned the car it felt like it was about to turn over, even at a very slow speed. I bought some leaves for the back from Hank Lee and I will combine the new to me and the old leaves but build it to 10 leaves total since both are old and may be weak also. I can always remove a leaf if the ride is too rough. Frank, the measurements were right on, thank you for all your research.
Thank you guys for all the very useful information, now it is time for me to get to work. Frank