68 - 72 chevelle rear coils

[79izfine]

read the previous post on lowering the rear it is said the chevelle would lower it 3 " i went on napa auto site and looked up a 68,69,70 the 68 was different than the 69/70 ,,,,, when i looked up the 68 i entered as a 396ss 2 dr hardtop heres the specs for the 68
I.D.:5.57"
Wire Diameter:.593"
Load Height:9"
# of Coils:5.4
Design Load:602
Spring Rate:168
Free Height:12.6"
--------------------------------------------------------------------heres the 70 .D.:5.58"
Wire Diameter:.531"
Load Height:9"
# of Coils:5.44
Design Load:616
Spring Rate:119
Free Height:14.71" so i would like to know which will accomplish my goal looks to me the 68 but only want to do this 1 time my other question are the springs used in combonation with stock shocks ,,,,i have the cheap shocks with the small coil springs on them they are not adjustable thanks for your input

 

[t5montecarlo]

You can calculate the effect of a spring if you know the specs, and you can get the specs from the spring book (just as you already have).

The equation for what a spring does is F = kx, where F is the force applied (the weight of the car), k = the spring constant, and x = the amount the spring compresses.

If you look at the 1968 specs:
F = 602
k = 168
x = Free Height - Load Height = 3.6

With a load of 602 lbs, the 1968 spring should compress 3.6 inches. If you do the math, you will see the results are within a negligible difference.

So, if you look at the spring specs for a Malibu, you will be able look up the value for F. Then, you can determine the Load Height of the 1968 spring using the Malibu value for F.

F (Malibu) = 168 x (12.6 - Load Height)

Solving for Load Height:
-Load Height = F/168 - 12.6

Using the 1968 specs as an example, -Load Height is -9.0xxx, or Load Height = 9.0xxx.

If the Design Load for your Malibu, as listed in the spring book, is higher than the 1968, then the 1968 spring will lower your car. If the Malibu Design Load is lower, then the 1968 spring will raise the rear of your car.

 

[79izfine]

this is the spec for 79 2dr bu I.D.:5.57"
Wire Diameter:.562"
Load Height:8.5"
# of Coils:6.13
Design Load:760
Spring Rate:122
Free Height:14.75"

 

[t5montecarlo]

F (1979 Malibu) = 760
k (1968) = 168
Free Height (1968) = 12.6

Solving for Load Height:
-Load Height = 760/168 - 12.6
Load Height = 8.08 inches

The Load Height of the 1979 Malibu spring is 8.5 inches. Therefore, if you use the 1968 spring, the rear of the car will sit approx 0.5 inches lower than if using the 1979 Malibu spring.

 

[79izfine]

guess .5 isnt enough this is the post i read malibuluvur stated 68 - 72 chevelle dropped his car 2-3" then another said 87 camaro will do the same just trying to lower mine on the cheap my car is basically nose diving i wish i could understand the formula thanks i will look up the camaro specs maybe you could calculate for me if you dont mind thanks again

 

[malibulvr]

I thought I stated that the coils that I used in my car were factory stock original used coils, not new replacements. I have used them many times but never bought a new replacement set, always used factory stock original used coils. I would think that the used coils would at least loose some of their rate over the 30+ years of use, just like alot of the original ones on the Gbody cars. Probably why they lower the car, but I've never had a problem with them and they always rode fine. If you look around you might can find a set of used bell tech or hotchkis rear springs for cheap. I was offered a new uninstalled set of bell tech rear lowering springs today here local for $75, so don't give up, if you put the effort into it and look hard they can be found. Wish you luck!

 

[79izfine]

my bad sorry i was thinking of other car springs to use one 72 vega thinking the rear of the malibu is heavier and will compress but the diameter is smaller