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Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22720
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
Here's what Chevy(and Zora) thought was best for the IRS Corvette rear springs...
Standard spring rates:
63... 192#
64-74...140# (1st stage) 196#(2nd stage)
75...196#
76-77...196#
Heavy duty:
63-77...305#
78-79...307#
80-82...266#
There are differences in a lot of the steel springs, as far as how many leaves they have, the design load(weight), and thickness of the leaves.
The 64-74 standard spring is the only one that is a "two stage" spring, meaning it is rated at two different levels of compression. The higher rating(196#) is with the spring almost 4 inches past "flat"!!!
All the other springs maintain the nominal rating thru-out their travel.
So...a 300# spring would have the same rating(approx) as the factory HP suspension. This would include the Z07, and the "Gymkahana" set-ups.
This is one reason I always question the logic of using some of the aftermarket, 340#-370# springs...
Granted, tire design has come a long way since then, but...Adams' Apple 2007-03-15 20:58:20
Standard spring rates:
63... 192#
64-74...140# (1st stage) 196#(2nd stage)
75...196#
76-77...196#
Heavy duty:
63-77...305#
78-79...307#
80-82...266#
There are differences in a lot of the steel springs, as far as how many leaves they have, the design load(weight), and thickness of the leaves.
The 64-74 standard spring is the only one that is a "two stage" spring, meaning it is rated at two different levels of compression. The higher rating(196#) is with the spring almost 4 inches past "flat"!!!
All the other springs maintain the nominal rating thru-out their travel.
So...a 300# spring would have the same rating(approx) as the factory HP suspension. This would include the Z07, and the "Gymkahana" set-ups.
This is one reason I always question the logic of using some of the aftermarket, 340#-370# springs...
Granted, tire design has come a long way since then, but...
Joel Adams
C3VR Lifetime Member #56 
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(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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j
Very helpful - thanks for the info Joel!
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Lifetime Member
Moderator
Send PMModerator
Duncanville, TX - USA
Joined: 11/8/2003
Posts: 22720
Vette(s): #1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/
Am-Fm/map light National/Regional/Chapter NCRS "Top Flight"
#2-1985 Bright Red/Carmine Cp.L-98/auto
Member: NCRS, NCRS Texas, Corvette Legends of Texas
I just can't understand someone wanting to make their car ride like a wagon...but, then again, I am an old fart.
I like to be comfortable when cruizin...
I like to be comfortable when cruizin...Joel Adams
C3VR Lifetime Member #56
My Link
(click for Texas-sized view!) NCRS
"Money can't buy happiness -- but somehow it's more comforting to cry in a CORVETTE than in a Kia"
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I see where the 78/79 gymkhana spring rates are the stiffest. I'll vouch for that! It can be a teeth jarring ride as is, much less going stiffer. Then again, I'm an old fart too! I don't even like LOUD exhaust
. Mike
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