Rear Leaf spring force measurement

[Steve L.]

Here is an easy method for measuring the condition of the rear leaf spring(73 coupe-standard spring). I don't know if anyone else has done this- I don't recall seeing this before. All you need is a bathroom scale, tape measure and a wheel dolly plus about half an hour of time.

Each leaf is measured independantly. I've compared my original with a new Dr Rebuild spring(yes, I know, I should have bought Eaton, but I didn't know better at the time).

I've included the data that I got in the second JPEG.

You can immediately see, that the repro spring is a lot stiffer.

My original large spring (#1) broke at the center bolt, so I need to replace that one for sure.

Looking at the data shows that spring #2 looks weak, so I'll replace that one. I don't see an obvious problem with it.

Spring #6 on both my original and the repro have the same spring rate so I'll replace that one as well.

My originals have rust pits in them but I don't want to use all the leaves out of the new spring because of the ride height problem.

It would be nice if someone could do this test on an Eaton spring and on a rust free original so that people could test their own springs and compare.

BTW, it's easy to put the curl on the spring ends yourself. Also, each spring end on the original is skived on each side about 1.85 inch long and 0.1inch deep- no one seems to every mention that for originality.

[Gary B.]

Rear leaf spring force measurement

Steve,

That's a nice test setup you created to measure the stiffness of each leaf.

Back in 1999 I did some testing of whole, assembled rear leaf springs and I reported some of the results in an article in the Corvette Restorer. To do the tests I used a servo-hydraulic testing machine I had access to and the test load went up to around 1,400 lbs, so not something you want to try with dead weights in your garage.

Gary Beaupre
Northern California Chapter

[Steve L.]

Re: Rear Leaf spring force measurement

Gary,
I too used to have access to an Instron and a MTS, but no longer.
So, this is the poor man's set-up.

[Steve L.]

Re: Rear leaf spring force measurement

Gary,
The web site for Eaton springs for corvettes shows that at full deflecton the load is 1320 lbs. They don't say whether this is at the center of the spring or at each end.

The car weights around 3200lbs so the back half would be about 1600 lbs which is more than the 1320 lbs. I would then assume that the Eaton load must be on each end for a total of 2640lbs at the center.

When you did your test (MTS I assume), did you load it at the center or on the end only?

[Gary B.]

Re: Rear leaf spring force measurement

Gary,
The web site for Eaton springs for corvettes shows that at full deflecton the load is 1320 lbs. They don't say whether this is at the center of the spring or at each end.

The car weights around 3200lbs so the back half would be about 1600 lbs which is more than the 1320 lbs. I would then assume that the Eaton load must be on each end for a total of 2640lbs at the center.

When you did your test (MTS I assume), did you load it at the center or on the end only?

I applied the load to the center of the spring. I had each end supported on rollers, so the ends were free to translate outward horizontally.

Gary