Rear Spring?

[1929]

Should these rear springs be changed after 85 years of service, are they still worth keeping? but, how do I know its original and wasn't changed already? When I had disassembled the rear spring apart, it didn't fly or shoot to the moon, from what I remember, I think it spread about 8 inches total.

[Mitch//pa]

IMO it's a no brainer to replace it...even if it did have tension I would replace it
Why screw around its apart and out..
Good luck

[Joe K]

Your call perhaps.

I've always dabbled with 10 leaf springs, particularly of the pickup truck variety. Oversprung the truck are, and I would say there was no need to change out a spring - except maybe to paint and restore using the John Deere Cornhead grease between the leaves.

But others who have a 7 (roadster with dummy leaf) or 8 or somewhat less than a pickup spring might have to make a change-out to prevent the dangerous sagging or leaning to the driver's side.

There are specs out there for the various leaves found in a Model A Spring. Contrary to common belief, the spring was a rather ingeniously designed piece of work not the least of which was to allow Henry to use a limited production of leaf thicknesses under a variety of loading situation.

With your spring disassembled you can look on Marco's "spring table" and determine if your spring is original, a modern replacement, or something somebody made up of loose pieces. (very common in the days of the Original Great Depression when people wore it out, fixed it up, and made do with what they had on hand.)

Thanks to Tom Wesenberg for putting Marco's chart out there for all to see - Tom you're at the top of the Google Search for "Marco's Spring Chart." Note particularly the rather uniquely shaped leaf cross sections, and the varying thickness of leaves.

https://www.fordbarn.com/forum/showthread.php?t=62383

Modern reproductions springs vary in their quality. At one point I bought a front spring from JC Whitney (remember them?) and found the spring to be non-tapered non shaped leaf, and all leaves the same thickness - I.e. a recycled trailer spring. The original Model A front spring is a little more than that.

Re-cambering a spring can work - for a while - but are known for sooner or later sagging to the original degree - or more. I confess with my truck springs to have not tried this remedy.

Probably the best reproduction springs can be bought from http://www.a-springs.com/ These are supposedly made to the original Ford specifications. I have not verified this. Last I knew there was a waiting list for new springs.

Hope this helps,
Joe K

[TinCup]

I have to go with the replace option. I tried to repurpose what I thought were two good rear springs and turned out neither were worth messing with. They looked good out of the car but when I put them under the coupe they leaned to one side. I even switched every other leaf to try to offset this but when they are gone I guess they are gone.

[1929]

What is the best way to determine if the spring is tired while in the car?

[hardtimes]

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Originally Posted by 1929

What is the best way to determine if the spring is tired while in the car?

Look at you car from rear. If it appears to be 'leaning' to one side, maybe spring broke/weak...OR shifted.
At the least, if original spring, take it apart and inspect. Leafs may be WEAK, cracked and/or broken, which will also show as a sagging look.
Also, if original set up, the spring eyes and attaching parts will most likely be worn out , i.e- bushings, etc.
In other words, if it is original equipment ,, it needs attention/rebuild/new.
My original rear '30 roadster spring had three broken leaves, worn out bushings and other parts.

[wrndln]

My 28 coupe leaned to the right about 3/4" - noticeable. I decided to reverse the rear original spring that I sandblasted lubed and painted, thinking that would level it or possibly then lean to the passenger side. I am pretty sure I randomly reassembled the spring leaves as I didn't mark them when I disassembled the spring. I was stunned that it made absolutely no difference. I marked the assembled spring before reversing it to make sure I didn't absentmindedly put it back the same way it originally was. I still can't explain why this happened - made no difference.
Rusty Nelson

[1929]

Originally Posted by hardtimes

Look at you car from rear. If it appears to be 'leaning' to one side, maybe spring broke/weak...OR shifted.
At the least, if original spring, take it apart and inspect. Leafs may be WEAK, cracked and/or broken, which will also show as a sagging look.
Also, if original set up, the spring eyes and attaching parts will most likely be worn out , i.e- bushings, etc.
In other words, if it is original equipment ,, it needs attention/rebuild/new.
My original rear '30 roadster spring had three broken leaves, worn out bushings and other parts.

Its not leaning, no springs broken. I had taken the spring out, sanded and painted every leaf
and put it back on. A friend of mine thinks its not working as good as the new front spring, he thinks the front spring handles the bumps much better then the rear spring, I don't notice the difference that he is talking about, that's why I had the initial question.

[Pete]

Originally Posted by 1929

Should these rear springs be changed after 85 years of service, are they still worth keeping? but, how do I know its original and wasn't changed already? When I had disassembled the rear spring apart, it didn't fly or shoot to the moon, from what I remember, I think it spread about 8 inches total.

Here is one way to do it. This has been posted several times before on here and the early V8 forum.


Reconditioning a model A spring.

To completely recondition a spring, after it is out and on the bench, I use two large C clamps, one on each side of the center bolt. I pull them up tight and take the nut off of the center bolt. I then SLOWLY LET THE C CLAMPS OUT EQUALLY till the spring is relaxed.
I then glass bead all of the leaves to get rid of all debris. Then inspect the eyes for wear. If worn, discard that leaf and have a new one made at the spring shop.
Then I magnaflux them. If all is ok, I then take them to a spring shop to have them re-heatreated. Steel does not wear out, it just gets fatigued. Re-heatreating returns it to original.
Aftre I get the leaves back, I inspect the top of all the leaves for grooving.
If grooved, grind and taper the tops of all the leaves for the last 3 inches back from the ends.
The number of leaves you use will depend on the final weight of the car
and the "ride" you want. On a typical model A it is possible to get a
100 lb. per inch spring rate which will give a very comfortable "touring ride". Have the shocks disconnected when checking spring rates. The easiest way to check spring rate is measure the height of a point on the front bumper. Apply a known weight to the front bumper such as a 200 lb. person. Measure the same point again. say it went down 2 inches. You have roughly a 100 lb per inch spring rate on the front.
DO NOT USE GREASE BETWEEN THE LEAVES. DO NOT use paint either. It will only attract dirt and then you have grinding cpmpound. I Parkerize the leaves (optional) and then spray them all over with SlipPlate (trade name) which is a graphite spray or Moly Kote (trade name) which is a molybdenem disulfide base spray.
I use 1/16 UHMW plastic between the leaves. This is similar to Teflon but
about 1/3 the price. This is optional but really decreases friction and prolongs spring life.
After determining the final configuration of the spring I wrap it with black electrical tape from the eyes to the U bolts. This keeps dirt out. There are commercial spring covers available also.
If you use a reversed eye main leaf, be sure the second leaf is short enough that there
is no way it can bottom on the eye when at full compression.
Sometimes the original spring clips will not reach over the spring after the UHMW is added.
It is a simple matter to fabricate ones that will.
The inside top of the cross member where the spring seats, usually has a radius.
BE SURE the top leaf of the spring has a radius to match. A sharp corner on the spring leaf can cause a cracked cross member.
I use moly filled Delrin shackle bushings because they have almost no friction and they never wear out. No tools required to install them also.

[Joe K]

DO NOT USE GREASE BETWEEN THE LEAVES. DO NOT use paint either.

I confess I stopped short when I read this - but reading on...

It will only attract dirt and then you have grinding compound.

This true - and why they did then and now a quick trade in spring covers. (and in the day a device which injected grease BETWEEN the leaves - the theory being it would drive out all the dirt.)

But I've always wanted to try the Teflon route - or something similar. One of the things which held me back was the thickness of the teflon strips - and building up the spring stack thickness to the point where the spring clips don't fit.

Sometimes the original spring clips will not reach over the spring after the UHMW is added.

I see you have anticipated my concern.

Joe K