I have a 7 leaf Gymkhana replacement spring for $50.

 

I replaced mine with a 7 leaf

 

I replaced mine with a 7 leaf

 

isn't a 7 leaf stiffer?

 

Hi Bh,
This information is from Eaton Spring.

"The most popular rear leaf springs used were 2 different versions of a 9 leaf springs and a 7 leaf spring. A 10 leaf spring was used very sparingly. But we will not talk about it.

The diferences between the springs were their rates. The down and dirty description of rate is it is the amount of weight required to deflect a spring one inch. The higher the rate, the stiffer the spring.

The 7 leaf spring has a rate of 305lbs.

The 9 leaf spring which all 9 leaves are curved has a rate of 196lbs.

The 9 leaf spring which the 1st 6 leaves are curved and the shortest 3 leaves are straight is a 2 stage or variable rate spring. It's rate starts at 140lbs and increases to 196lbs when all the leaves are touching.

The loads they were designed to carry are all pretty much the same.

The 7 leaf has a design load of 1,325 lbs. Both 9 leaf springs have a design load of 1,360 lbs.

All 3 springs are designed to have a 3/8 reverse arch when at their design load.

In order to accomplish the same spring height when under load with the spring having different spring rates, the free arch of each spring is different.

The free arch of the 7 leaf spring is 5-7/8 inches. The 9 leaf spring is 7-1/2 inches and the 6/3 spring is 8-11/16 inches.

The correct way to measure the free arch is for the spring to be off the vehicle. Place a straight edge across the ends of the spring and measure down to the main plate next to the centerbolt.

Whle we use the correct type of steel, SAE 5160 High Alloy Spring Steel, the thickness's have been adjusted to sizes the steel mills now produce. Way back when the mills would produce quantities as low as 5 tons of a size. Today 22 tons is the bare minimum of one size they will produce. And that is a lot of Corvette springs.

While the overall thickness of the springs have slightly increased, the fit, feel and performance of the springs are unchanged. However the free arches have been lowered form the original factory specs in order to maintain stock ride height."

Regards,
Alan

 

So what is recommended? 9 or 7 leaf? If I like a softer ride I should go with 9 leaf? How much stiffer does the 7 leaf feel?

 

Hi Bh,
I think this is the important sentence:

"The 9 leaf spring in which the 1st 6 leaves are curved and the shortest 3 leaves are straight is a 2 stage or variable rate spring. It's rate starts at 140lbs and increases to 196lbs when all the leaves are touching."

I believe original front springs have 4 coils that are closer together to accomplish the same thing…. variable rate.
Regards,
Alan

You can see the close coils in this photo. They should be at the top when the spring is installed.

 

I think I'll go with the 9 leaf spring. Any recommendations on the best place to source one?

 

Hi,
I believe I'd begin by talking to the folks at:

Eaton Spring
and
Muskegon Brake.

Good Luck!
Regards,
Alan

 

I agree I just it mine from them ,perfect fit ,just make sure
The bolts are the right length .

 

If you were near Dallas, i'd give you the gymkana spring set i took off my 1980. i replaced it with a composite mono spring.