Leaf spring identification

[Gary B.]

Re: Leaf spring identification

Thomas,

If you search thru the TDB archives you will find postings that list the spring rate for the 1963 9-leaf, rear spring variously as 162, 163, 192, and 196 lb/in. My notes say the 1963 AMA specs list a spring rate of 162 lb/in for the 3794095, 9-leaf spring. However, a GM engineering drawing that I had access to lists a rate of 192 lb/in for PN 3794095. The same engineering drawing also lists other GM springs including a 7-leaf spring with a rate of 162 lb/in. Given that the leaf thicknesses for the 63 spring are the same as for the 64-74 9-leaf spring, which we “know” has a dual rate of 140/196, with the 196 rate applicable after all leaves are engaged, I would tend to believe the 192 lb/in number that is given in the GM engineering drawing that I viewed for the ‘63 9-leaf spring.

Gary

[Thomas B.]

Re: Leaf spring identification

My sources are the Corvette Specs available through Heritage Center and an article by Larry Linder. See attached.

By the way, I took another look at my spring and the 7 leaves I referred to in a previous reply as thinner are actually close in thickness to the top and bottom leaves. They taper down to something like 1/16" at the ends.

Hard to measure the leaf thickness on the car but I’d bet all leaves are within the .214 (7/32”) and .194 (3/16”) thickness range.

[Gary B.]

Re: Leaf spring identification

Thomas,

The 162 rate in the Heritage Center document might have come from the 162 in the AMA specs, which could be a typo, 162 vs 192. I wouldn’t bet the farm in it, but I have the most confidence in the 192 value in GM engineering drawing. That value is close to the 196 rate for the 64-74 spring, and that similarly makes sense to me. Obviously, some numbers are wrong, and once they are in certain documents, like the AMA specs, the wrong numbers will be repeated.

Gary

[Thomas B.]

Re: Leaf spring identification

Harry,
What is the initial arch dimension on your spring before installation?

Tom

[Harry S.]

Re: Leaf spring identification

Harry,
What is the initial arch dimension on your spring before installation?

Tom

Tom, pour a drink and have a read.

https://www.forums.ncrs.org/showthre...ht=1963+spring

[Duke W.]

Re: Leaf spring identification

There is missing, conflicting, and likely some incorrect information in the AMA specs regarding springs. At some point in the seventies as the Corvette got heavier, spring rates were increased. For example the '77 specs list the spring/wheel rates as follows in lbs/in.

Front: 320/117.6
Rear: 196/151.4

There is no indication that they are variable rate, so I assume they are constant rate.

The years of variable rate springs the specs don't list the min/max rate or always specify the load condition for the quoted rate. For example, the rate at "design load", which is gross weight - curb weight plus about 500 pounds - would be higher than at curb weight or some load condition less than "design."

If someone wants to go through the entire c2/3 AMA specs you might be able to sort it all out.

Duke

[Joe L.]

Re: Leaf spring identification

There is missing, conflicting, and likely some incorrect information in the AMA specs regarding springs. At some point in the seventies as the Corvette got heavier, spring rates were increased. For example the '77 specs list the spring/wheel rates as follows in lbs/in.

Front: 320/117.6
Rear: 196/151.4

There is no indication that they are variable rate, so I assume they are constant rate.

The years of variable rate springs the specs don't list the min/max rate or always specify the load condition for the quoted rate. For example, the rate at "design load", which is gross weight - curb weight plus about 500 pounds - would be higher than at curb weight or some load condition less than "design."

If someone wants to go through the entire c2/3 AMA specs you might be able to sort it all out.

Duke

Duke------

The rear springs changed for the 1975 model year with several changes thereafter.

[Thomas B.]

Re: Leaf spring identification

Duke,
Where can I get a copy of the AMA specifications?

Tom

[Leif A.]

Re: Leaf spring identification

Duke,
Where can I get a copy of the AMA specifications?

Tom

Tom,
The first 35-40 pages of the GM Heritage document, that you mentioned in post #17, are the AMA specs for your car.

[Thomas B.]

[Joe L.]

Re: Leaf spring identification

Duke,
Where can I get a copy of the AMA specifications?

Tom

Tom------

Keep in mind that there are sometimes inaccuracies in the AMA specs. I believe the cause of this is that these specs were transmitted to the AMA and published before the final specs and configurations for the model year were adopted. In most cases, once published they were not subsequently corrected.

[Thomas B.]

Re: Leaf spring identification

Joe,
So no other source with final specs?

Tom

[Gary B.]

Re: Leaf spring identification

I place a lot of faith in the GM engineering drawings, provided you are certain of the GM part number.

Gary

[Joe L.]

Re: Leaf spring identification

I place a lot of faith in the GM engineering drawings, provided you are certain of the GM part number.

Gary

Gary------


Yes, the engineering drawings are accurate in all cases of which I am familiar.

[Thomas B.]

Re: Leaf spring identification

Where can I find them?