Spring rate of 9-leaf rear spring?

[Chris E.]

I did some searching but didn't find it.

Does anyone know what the spring rate should be of a base suspension 9-leaf rear spring for a 67?

[Michael F.]

Re: Spring rate of 9-leaf rear spring?

I believe thats 140-196lbs, it's a variable rate spring.

Heres a good link for future referrence. Thats assuming their data is accurate.

http://www.eatonsprings.com/53-82corvette.html

[Chris E.]

Re: Spring rate of 9-leaf rear spring?

I believe thats 140-196lbs, it's a variable rate spring.

Heres a good link for future referrence. Thats assuming their data is accurate.

http://www.eatonsprings.com/53-82corvette.html

That is the data I was trying to confirm. Looking for a different source for the data, other than Eaton.

[Michael F.]

Re: Spring rate of 9-leaf rear spring?

That is the data I was trying to confirm. Looking for a different source for the data, other than Eaton.

I think the posted data is correct. Not sure about their actual spring rates.

I had to go to the 7 leaf. Even that seems a bit soft. Could be my 250lb a$$ weighing it down.

[Gary B.]

Re: Spring rate of 9-leaf rear spring?

That is the data I was trying to confirm. Looking for a different source for the data, other than Eaton.

Chris,

Spring rate data from a GM source is in one or more of my leaf spring articles in the Restorer from some years ago. Unfortunately, I don't have the articles handy, but they should be on the Restorer CDs.

Gary

[John H.]

Re: Spring rate of 9-leaf rear spring?

Chris -

Both the Chevrolet Engineering Specifications package and the AMA Submission detail show the 9-leaf spring with a rate of 140#/inch at design load (1360#). The 7-leaf F41 spring is 305#/inch at design load.

[Ronald L.]

Re: Spring rate of 9-leaf rear spring?

Lots of complaints or guys installing longer spring hanger bolts due to too much arch, higher rate or a combination of both with the product these days causing the cars to sit too high in the rear.

[David H.]

Re: Spring rate of 9-leaf rear spring?

That is the data I was trying to confirm. Looking for a different source for the data, other than Eaton.

Here is a link to the GM Archives data kit for your year car:

http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html

Scroll down the page to "Corvette" and click "Show". Another page opens with various years - select the year ("1967" in your case). Accept the GM usage agreement and a pdf with your year's data is downloaded.

The pdf is a copy of the technical data available from GM archives. It contains information the dealer got, as-well-as information submitted to the American Manufacturers Association (AMA). In particular for 1967, information on the rear suspension is on pages 23 and 81 of the pdf.

As noted earlier, the Spring Rate is 140 lb. per inch - Rate at Wheel is 123 lb. per inch.

[Gary B.]

Repro 9-leaf rear spring

Lots of complaints or guys installing longer spring hanger bolts due to too much arch, higher rate or a combination of both with the product these days causing the cars to sit too high in the rear.

Ron,

When I think back over all the rear spring/ride height DB postings over the past 4 or 5 years, I think there are about equal numbers of postings from folks complaining about too high of a ride height and as there are from folks staying the ride height is spot on (specifically when using the repro Eaton Detroit 9-leaf spring). I believe John Hinckley is in the latter group. I don't know why some folks find a problem and others don't, but I bet some or most of the cause is related to not letting the suspension settle in for a reasonable amount of driving time. In any case, a good fraction of folks think the ride height provided with the Eaton spring is close to factory specs. And to be clear, I have no stake whatsoever in promoting the Eaton spring.

The decision that I described in one of the Restorer articles on leaf springs from some years ago was to use a new main leaf from Eaton and retain leaves 2 thru 9 from my original spring. I think that approach will pretty much guarantee the correct ride height.

If and when the repro 9-leaf spring to be sold by America's Finest Corvettes come to market, restorers may have an option to the Eaton.

Gary

[Chris E.]

Re: Spring rate of 9-leaf rear spring?

I just put a new Eaton 9 leaf in my car and drove it only a few miles.

The ride height is REALLY close.



I called the guys at Eaton, and they said the spring needs between 50-100 miles to settle in. Hoping to address that on Saturday and can post another picture.

A couple of interesting comments from Eaton on springs.

1. Don't paint the mating surface between the liners. As the paint fails, it creates a gap between the spring leaves and can cause premature failure of the spring.

2. Other GM divisions had TONS of springs for each model car. The spring rates were defined based on the options on the car. More options = heavier car = strong spring needed. Corvette is one of the few makes that had only one spring for ALL of the following choices (convertible with no options, convertible with both tops, and coupe). If you think about the weight differences between those three options, we ideally should have a different spring. Instead, the AIM specifies a slightly different ride height.

[Michael F.]

Re: Repro 9-leaf rear spring

Ron,

When I think back over all the rear spring/ride height DB postings over the past 4 or 5 years, I think there are about equal numbers of postings from folks complaining about too high of a ride height and as there are from folks staying the ride height is spot on (specifically when using the repro Eaton Detroit 9-leaf spring). I believe John Hinckley is in the latter group. I don't know why some folks find a problem and others don't, but I bet some or most of the cause is related to not letting the suspension settle in for a reasonable amount of driving time. In any case, a good fraction of folks think the ride height provided with the Eaton spring is close to factory specs. And to be clear, I have no stake whatsoever in promoting the Eaton spring.

The decision that I described in one of the Restorer articles on leaf springs from some years ago was to use a new main leaf from Eaton and retain leaves 2 thru 9 from my original spring. I think that approach will pretty much guarantee the correct ride height.

If and when the repro 9-leaf spring to be sold by America's Finest Corvettes come to market, restorers may have an option to the Eaton.

Gary

Eaton springs have given me a perfect ride height. It was the lack of stiffness on the standard 140/195 rear leaf that drove me nuts. The 305 lb is just right.

I was wondering if their spring rates are accurate? Or it could be the average C2 driver weighs 100lbs more today than they did in 1963.

Other than that, Eaton has been an excellent providor.

All springs require a bit of settling.

[Gary B.]

Re: Spring rate of 9-leaf rear spring?

1. Don't paint the mating surface between the liners. As the paint fails, it creates a gap between the spring leaves and can cause premature failure of the spring.

That's very odd to hear. The bottom (tension) surface of each leaf in the spring was painted according to the GM engng drawings. And some of those painted GM springs have been around for 45 or more years and are still going strong.

Gary

[Gary B.]

Re: Repro 9-leaf rear spring

... Or it could be the average C2 driver weighs 100lbs more today than they did in 1963.

I bet the US Surgeon General would agree with that hypothesis.

Gary

[Ronald L.]

Re: Spring rate of 9-leaf rear spring?

All I can say is that a local shop is using lots of long bolt kits due to the problems, these are mostly C3 cars but the basics are pretty much the same, including the loaded vehicle weight.

[Michael F.]

Re: Spring rate of 9-leaf rear spring?

Here is a link to the GM Archives data kit for your year car:

http://www.gmheritagecenter.com/gm-heritage-archive/vehicle-information-kits.html

Scroll down the page to "Corvette" and click "Show". Another page opens with various years - select the year ("1967" in your case). Accept the GM usage agreement and a pdf with your year's data is downloaded.

The pdf is a copy of the technical data available from GM archives. It contains information the dealer got, as-well-as information submitted to the American Manufacturers Association (AMA). In particular for 1967, information on the rear suspension is on pages 23 and 81 of the pdf.

As noted earlier, the Spring Rate is 140 lb. per inch - Rate at Wheel is 123 lb. per inch.

Then GM did NOT offer a dual or progressive rate rear leaf spring?