8 leaf to 7 leaf rear spring conversion

[SAXBY2]

With an 8 leaf rear spring, what leaf can be removed to make a 7 leaf roadster spring ?
Both size spring bars to the crossmember are on hand.
The spring chart frequently posted shows the numbering starting at the bottom, and it appears that the #8 or 2nd spring from the top of the 8 leaf could be removed to get close to the 7 leaf profile? The removed leaf could be used as the dummy under the #1 or largest leaf if needed to make up the difference for the spring bars.

 

[wrndln]

I believe Marco created a picture of the different rear springs. If I remember correctly one of the roadster springs were slightly less thick than the normal leafs. I don't think the difference is substantial. I would think a regular spring would work OK in place of the thinner leaf. I have the drawing Marco made and posted it below.

Rusty Nelson

 

[Joe K]

In examining the chart above, there appear to be two significant and one insignificant changes between spring "C" (7 leaf) and "B" (8 leaf.)

1. Leaf No. 9 is left out in "C"
2. Leaf No. 4 is "thinner" in "C"
3. Leaf Dummy is added in "C"

There may be other differences such as overall individual leaf length or caul radius (pre-tensioning) which are not shown on the chart.

A place to start would be to remove leaf 9. A Dummy is added only so the spring clamps used on B can also be used on C - you can buy a full size leaf of any size on Ebay for relatively small money, and cut it down to make the dummy since it exists only to take up space with no resilience or load carrying input.

That leaf No. 4 would then be the only significant difference. I might imagine enough "relaxation" of the pre-tensioning would make the difference in actual thickness a moot point. A little additional thickness MIGHT be a good thing lest you ride too low with an original 7 leaf spring now nearly 90 years old.

There are prints showing detailed dimensions of each leaf in the Ford Archive. Someone here may have and be willing to share. Of interest particularly No. 4.

This is one of those days I wish the board had an "information repository" for prints recovered from the Ford Archive and made available via the board to everyone.

Joe K

 

[SAXBY2]

#9 leaf from the bottom doesn't appear to be part of the 7 leaf or 8 leaf spring makeup , so perhaps removing #8 is the removed one. The added thickness as posted for leaf #4 for the 8 spring setup could be beneficial for a worn spring , so that leaf could remain unchanged. We can try removing #8 and see if it fits as the dummy.

 

[Joe K]

#9 leaf from the bottom doesn't appear to be part of the 7 leaf or 8 leaf spring makeup , so perhaps removing #8 is the removed one.

You're right! My mind's eye got hung up in the "red line" (i.e. B spring)

If you could come up with a No. 6 leaf from springs C, B or A you would be all set after cutting down.

Again, a drawing of the spring assemblies would be best as from this you have the leaf thicknesses (there are only three options discounting the "beveling") but you don't have the actual spring leaf "lengths" (or caul bending/pre-tensioning)

Ebay currently has two rear spring leaves (2-1/4" wide) for sale. One 12" long, the other 15". I can't tell you which leaf in particular these are or the spring application. There may be something there for you.

Joe K

 

[duke36]

Putting aside the thicknesses, why not use the shortest #10 leaf as the dummy and bevel the top edges of the #8 leaf to become the top of the 7 leaf spring ? Or use the #8 longer leaf as the dummy and leave the #10 leaf as the top of the 7 leaf spring? One leaf has to be removed from the existing 8 leaf pack and not sure which one is best not having an original 7 leaf spring to examine ?

 

[Phil Brown]

Just went through this for my coupe besause I wanted the rear down just a bit.
#10 and #7 are the same, the top is contoured and beveled to fit the cross member.
Move #8 under the main (#1 spring) to become the dummy or spacer spring
I trimmed the length of the new dummy to look more correct but not really necessary.
I don't think the thickness difference of the #4 leaf in the 8 spring pack will be an issue
Work safe that spring can hurt ya .

 

[rotorwrench]

A person first has to verify if their spring meets the dimensions in Marko's breakdown. No telling how many aftermarket or different manufacturers springs are floating around out there. I know that the current new offshore reproduction ones are different in thickness on the individual leaves. Eaton Detroit is the only current manufacturer a person can talk to about their springs.