Replacing only the main leaf spring with a new one?

[M2M]

I noticed that spring guru Travis Cook is selling just the main leaf for both front and rear. Much cheaper than buying a whole new spring. Does it make sense to replace just the main leaf on your springs if you feel they've lost their bounce or height?

 

[Rusty Sills]

I presume you are seeking a 'real' answer to your specific question. So I provide the following with an assumption (since you didn't say) that you are not working on a 100 point restoration ... and the fact that something is only "original,' once", anyway.



I have done this several times, successfully. However, I had several solid and complete springs to work from in selecting well inspected replacement leaves. To my eye, which is the only one I can speak of, one has to have some idea of what would constitute those leaves which seem 'iffy'. Obviously, leaves that are cracked, corroded or significantly(?) gouged ... or showing considerable 'de-arching(?) (in relationship to those in succession in the stack) would not be in the running. But that is where the 'several complete springs come into play, as you can make comparisons of tension, arch, etc.


As far as a complete 'new' replacement spring ... the aftermarket supplier would have to have actually engineered each leaf to Ford engineering spec, for it to be factually, "right". So the question is, would the complete replacement be much better than a reconstituted (for lack of a better term) assembly. But, I cannot speak to other's ability to make a adequate guestimation as I have a mechanical engineering background.



It has been my experience that many 'aftermarket' parts are very often 'sorta close', but not to spec with the original Ford engineering (in spite of what is touted), ie., cotter pin holes mislocated in "u" bolts, brake spring wire to heavy guage, off the shelf castle nut sent as proper(?) replacement to the much taller 'real' spindle nuts, etc. I could go on for awhile on that issue ... but that does not address your question.


Bottom line. If you think you have the 'eye' for a good assessment, or if you have someone nearby to collaborate with, it's your call. You will know fairly quickly when you put the car on the ground.

 

[Rusty Sills]

M2M.


In addressing your question, it seems that I overlooked that you stated that your car had been in constant usage 24/7/365 for the past 90 years.



My apologies for stating my opinion .... misguided as it was.


RS

 

[ryanheacox]

My opinion, obviously replacing the spring outright would be better and a longer lasting fix. Changing just the bottom leaf still leaves you with 9 old leaves on top of it.



However, if replacing the bottom leaf works, keeps the car going down the road well AND you are okay with the knowledge that it might not be the longest lasting repair then go for it.


If it were me and I was going through the time to pull the spring, front or rear, I'd just replace it. For the time you take disassembling the old spring and fitting the new bottom leaf it might make more sense just to buy a new spring. I'd rather not do the job twice.

 

[M2M]

M2M.


In addressing your question, it seems that I overlooked that you stated that your car had been in constant usage 24/7/365 for the past 90 years.



My apologies for stating my opinion .... misguided as it was.


RS

Where did I state that???

 

[Rusty Sills]

M2M,


My bad. I see that it wasn't you ... but another member who made that comment.


Please disregard my opinion and experience, for as a junior member, it is fitting that I defer to the opinions and experience of senior members.


RS

 

[woofa.express]

Hi M2M. Tell me please, is the truck you posted last year doing a rebuild?


Sorry all. I posted the above on the wrong thread. gary

 

[alexiskai]

It occurs to me that there are a ton of companies in the US (or wherever you are) that specialize in repairing leaf springs for trucks, trailers, RVs, etc., and I bet you could call up a couple of them and get an answer much more informed by the engineering and behavior of leaf springs then you're likely to get here.

 

[Patrick L.]

I think Rusty covered this pretty well.

I've been rebuilding springs on things from baby carriages to heavy trucks for decades. I have no issues with a repaired spring as long as its a quality repair.

I replaced broken leaves on my 'A' 45 yrs ago when I got it, with no issues since. You just need a good spring to get the extra leaves from, thats usually the tricky part.

 

[dumb person]

The bottom leaf holds to the axles. If you have doubts to it's strength, then replacing it is a good option.
It's only a bad option of the other leaves are rather poorly, as they do the heavy lifting.
So to answer your question, if you feel you lost bounce, the bottom one is only the first one to change out. Uppers may vary.

 

[SSsssteamer]

On my 1929 Tudor, I had sorted out the best leaves from many different used spring sources and I still had too much body roll and a soft spring at that. I even added an additional leaf spring to firm it up. After many years (50 years) of fighting the soft springs, I bought a whole new spring for the front. A world of difference. Seams that all the old spring leaves had lost their tension and they were allowing our Tudor to sag out on every opportunity. My advice, don't screw around with replacing the main leaf. For not much more money you can replace them all and do the job right.

 

[Randy in ca]

......... With these two facts in mind, let me ask you 2 questions:

1. Of the ten leaves in a Tudor spring isn't the main leaf the most important one as far as forming the arch (and height) and supplying the flex to the spring?

2. If the answer to question 1 is "yes"; wouldn't adding a new main leaf be better than not adding one? As far as matching leaves, in such a scenario 9 of the 10 leaves are already matched, with all of them sitting on the new main leaf.

[FONT=&quot]There’s no doubt that the shape and condition of the leaves above the main leaf has a definite effect on the overall shape and performance of the spring assembly. Each leaf moving from bottom to top should have a tighter curvature. That means that every time you add/clamp another leaf above, more curvature should be forced into the leaves below and the main leaf spring eyes become closer together. By example, all rear main leaves should have the same eye-to-eye distance when loose, but by the time they’re assembled those springs with 2 or 3 more leaves should measure up to 2” shorter eye-to-eye due the additional force applied by the curvature of the additional top leaves. The Roadster spring, with the least number of leaves, should have the flattest appearance when assembled as well as the largest eye-to-eye distance. An old catalogue I have shows the assembled Roadster rear spring eye-to-eye dimension as being 40" to 40-3/16" while those for other models range from 37-7/8" to 39-11/16" eye-to-eye when assembled.

[/FONT]

 

[alexiskai]

An old catalogue I have shows the assembled Roadster rear spring eye-to-eye dimension as being 40" to 40-3/16" while those for other models range from 37-7/8" to 39-11/16" eye-to-eye when assembled.

Is there a resource online showing the factory standard unweighted dimensions for the various front and rear springs? This would be a good resource for those of us looking at used springs or trying to assess the condition of our current springs.

 

[M2M]

The bottom leaf holds to the axles. If you have doubts to it's strength, then replacing it is a good option.
It's only a bad option of the other leaves are rather poorly, as they do the heavy lifting.
So to answer your question, if you feel you lost bounce, the bottom one is only the first one to change out. Uppers may vary.

[FONT=&quot]There’s no doubt that the shape and condition of the leaves above the main leaf has a definite effect on the overall shape and performance of the spring assembly. Each leaf moving from bottom to top should have a tighter curvature. That means that every time you add/clamp another leaf above, more curvature should be forced into the leaves below and the main leaf spring eyes become closer together. By example, all rear main leaves should have the same eye-to-eye distance when loose, but by the time they’re assembled those springs with 2 or 3 more leaves should measure up to 2” shorter eye-to-eye due the additional force applied by the curvature of the additional top leaves. The Roadster spring, with the least number of leaves, should have the flattest appearance when assembled as well as the largest eye-to-eye distance. An old catalogue I have shows the assembled Roadster rear spring eye-to-eye dimension as being 40" to 40-3/16" while those for other models range from 37-7/8" to 39-11/16" eye-to-eye when assembled. [/FONT]

Good answers that directly address my question about replacing only the main leaf with a new one.

 

[WHN]

A spring is NOT running gear. If a leaf in a spring breaks at 45mph there's no way on earth it will result in any harm to your children and grandchildren.

Interesting that you take this view with springs (it must be new, correct and perfect) while in another thread you advise the use of a 50/50 mix of STP and the fake "600w" oil the suppliers sell in transmissions. A transmission IS running gear. STP is NOT meant for transmissions. The oil the suppliers sell is NOT 600w. Using YOUR logic, you're risking the safety of your grandchildren.

You don't seem to have a coherent strategy/ideology about safety, restoration and maintenance.

As stated earlier, you and I seem to not be on the same plane.

I would just add that a broken main leaf in either a front or rear spring has the potential to create a REAL problem. Someone that doesn’t think that is the case really does not understand how these cars are set up.

I don’t know what I have said or done that has gotten you so upset. That’s your issue not mine.

Check with Webster’s. Running Gear is a noun, definition, wheels, axels, and springs. Sorry.

Please reframe from addressing me further.