Rear Spring with correct height 72

[Todd L.]

Where could a rear 9 leaf spring for a 72 be found that has the correct height? A company in California says they have them but, my friend has been waiting for several months, and keeps getting the "soon it will be available" run around. His frame is ready to be put together, so I know he is chomping at the bit, for a correct height spring.

[Gary B.]

Re: Rear Spring with correct height 72

Mike,

Call Eaton Detroit Spring. Lots of folks have used the 9-leaf Eaton spring and are happy with it. Do a google search to find their contact info.

Gary Beaupre

[Todd L.]

Re: Rear Spring with correct height 72

Have you used a spring from Eaton Detroit Spring, and did it provide the proper ride height?
Thanks

[Wayne B.]

Re: Rear Spring with correct height 72

I just finished putting a new nine leaf spring from Eaton on but you'll have to wait till Friday before I can give you a height as I need to take it down the street and let it settle before i torque the bolts the rest of the way (going to rain tomorrow). Mine's a 70 but should be the same height as yours.

[Todd L.]

Re: Rear Spring with correct height 72

I appreciate the input. And will wait to hear from you on ride height.

Todd

[Patrick H.]

Re: Rear Spring with correct height 72

I'd look for a good used one. I purchased one several years ago from a Corvette "junkyard" in California and it looked like new when I received it. New paint and liners, and it's good for another 40 years.

[Jack H.]

Re: Rear Spring with correct height 72

I agree with Pat's advice... There are more of these used/original 9-leaf springs out there at reasonable prices than you might think.

That's because it was 'vouge' for subsequent owners to go 'soup up' their cars by replacing the standard 9-leaf rear spring with a HD suspension 7-leaf OR by upgrading to an aftermarket 'monospring'...

[Gary B.]

Rear Spring with correct height 72

Todd,

I also agree with Patrick and Jack. In terms of correct ride hight and the best judging results, a good used original is the way to go. But if finding a good used original proves too challenging, the Eaton is currently the best option for a 9-leaf repro in my opinion. Perhaps a better 9-leaf repro will come on the market at some point in time.

If you read my 1st or 2nd Restorer articles on rear leaf springs from the early 2000s, you'll see that a combined approach is to use a new main leaf from a repro spring along with leaves 2-9 from an original spring. That would give you some added security that you've got a strong main leaf, with the advantage that the spring will judge well since judging deducts typically come from the incorrect geometry of turned-up ends on repros leaves 2-9. The Eaton spring will likely get a deduct from a savvy chassis judge because of the leaves 2-9 issue.

Gary

[Robert P.]

Re: Rear Spring with correct height 72

I purchased A 9 leaf from Eaton. Stripped the black paint, Painted it gray and replaced the liners. The car sits 2in. too high. They said they can re-bend the spring. I found a 9 leaf out of a 74, $50.00. I am going to install the used one in a few weeks. Bob

[Steve L.]

Re: Rear Spring with correct height 72

So if the gage thickness of the spring material is too thick( the original thickness not available anymore), I wonder if the spring rate can be compensated for by adding a slit that is maybe 3/8inch wide running the length from about 2 inches away from the center bolt to just short of the leaf just above so that the slit is not visable once the spring is assembled.

Eaton probably has design engineers who can calculate exactly how wide this slit needs to be so that even with a thicker spring, the spring rate can be ajusted to exactly what the original was and not have to compensated by flatening out the spring.

The slit could only be added on springs #2 through #5(#1 being the longest).

Just thinking out loud.

[Gary B.]

Rear Spring with correct height 72

Steve,

Adding a slit would affect the local stresses and potentially affect the strength and fatigue life of the spring. An easier solution would be to change the arch which would change the ride height w/o affecting the fatigue life. In the 2nd article on leaf springs that I wrote for the Restorer about 8 or 9 years ago, I tested an Eaton Spring and my measurements showed it had a free arch of 8.0" instead the 10" that is the design spec for the original GM 9-leaf spring. For my tests it seemed clear to me that Eaton had reduced the free arch to compensate for the fact the that stiffness of the Eaton spring was about 40% too high (200 vs. 140 lb/in), caused by the thicker spring stock they used. If Eaton decreased the arch further the ride height could be made closer to the GM spec.

Reducing the free arch is exactly what GM did with their 7-leaf spring, which has a much higher spring rate compared to the 9 leaf, and therefore needs a smaller arch in order to get a similar ride height.

Gary Beaupre
Northern California Chapter

[Steve L.]

Re: Rear Spring with correct height 72

Gary,
If the thickness of the spring is increased and the width, length is the same, reducing the arch may help the ride height, but the spring rate is still greater than the original. So, don't these repo springs give a much stiffer ride even thought they try and compensate for the ride height with a flatter spring?

I agree, the slit would tend to increase stresses and reduce fatigue, but that's why they have engineers( at least I would hope) at Eaton to figure this out and compensate.

But, then again, they would need to spend the design $$ on this so the business case could never be justified unless they did such a great job that everyone would buy only their replacement springs.

[Gary B.]

Rear Spring with correct height 72

Gary,
... don't these repo springs give a much stiffer ride even thought they try and compensate for the ride height with a flatter spring?

I probably wouldn't say "much" stiffer, but it is stiffer; 200 lb/in for the Eaton 9-leaf vs. 140 for the GM 9-leaf, where the 200 value comes from my tests using an MTS system. But remember, the GM 7-leaf has a stiffness of 305 lb/in, so the Eaton 9-leaf is closer to the GM 9-leaf than it is to the GM 7-leaf.

Back in my Restorer article from 8(?) years ago, I believe I was the first to suggest that one might use a new main leaf from an Eaton spring along with good, used leaves 2 thru 9 from an original GM spring. This combination should produce a ride height and stiffness that are only very slightly greater than the original GM values and the difference will be undetectable by eye or ride feel. And this combination spring should not be detectably different from an original GM spring from a cosmetic view, i.e., no judging deducts for incorrect ends on leaves 2 thru 9, which the Eaton repro suffers from. For safety reasons, I like the idea of using a brand new main leaf.

Gary

[Thomas S.]

Re: Rear Spring with correct height 72

I am disappointed to see that folks in this community are still going through this rear spring issue. I went through this in 2001/2002 before searching here and coming across Gary Beaupre's excellent articles and traded emails with Gary (Gary, not sure if you remember). I live outside Detroit and purchased the Eaton spring. My car also sat around 2" too high. Back then, I went to Eaton's shop and Mike Eaton admitted to me and a friend that he could not obtain the correct material and the leaf thickness was too thick. It sounds like this may still be the case. After some heated discussions, Mike Eaton took out some of the arch in the spring for me. The ordeal cost my over $300, not to mention the time the car was down and my sweat. The car with the reduced arch has the correct ride height, but I am not happy with the ride and would not recommend this solution. I recommend Gary's solution of replacing the main leaf on a good used spring with a new main leaf perhaps from Eaton's as he did at the time have the correct end treatments. Good luck with your effort.

[Bill C.]

Re: Rear Spring with correct height 72

Listen to Patrick --- it is the best way to attack this project.

My car had a cracked lower leaf, I found a junk yard 9 leaf, took it apart and refurbed my assembly with the lower leaf from the other.

My car sits at a perfect height and rides okay too.

Plus as an extra added bonus, you may be able to use the liners from the junk yard spring. The liner kits available today are plastic and after some time will bunch up and look TERRIBLE. The orinals were a thinner rubber material and were able to give with the arch/unarch of the springs.
Since the Ikonclad primer is not available anywhere (anymore), using the older liners is even more important. This primer was high in ZINC but also provide some lubrication (as I understand it).

Let us know how this works out....