Coil spring rate ?

[dq409]

Looking for someone who understands coil spring lingo !!
Here are the two examples,,,,application:`62 Impala SS 409

283 spring: wire size .672, free standing height 18.78",,
load rate 2263#,,rate load hgt. 324

409 spring:wire size .690, free standing height 16.893",,,
load rate 2052#,,rate load hgt. 403

The rate load hgt. is what I don`t understand.
From what I can guess is that the 409 spring will give you more lift under excelleration,,,yes/No ???,,,,dq

 

[TomO]

Very interesting. Hopefully someone knows something about coil springs!! I am still running the ones that were in the car when it had a 6 banger in it!!!!

 

[dq409]

Got this reply on CT,,,,,

The "rate load height" is the spring rate expressed in pounds per inch at the load height of the spring. Aftermarketers of coil springs give you a figure of the total load distributed over the spring travel from the free height to the loaded height of the coil spring.

The front coil springs just hold up the front of the car...they dont "give you more lift under acceleration". The way the front of a car lifts (or the rear lifts, or the whole car lifts) under acceleration is a function of the rear chassis/suspension links (in the case of a rear wheel drive car).

In your first example, 324#/" is the spring rate. It will take 324 pounds of vertical pressure to compress that spring to its Rated load height.. BUT....not only is the front spring not vertical in the car, but the spring is compressed by the lower a-arm which in effect is a lever acting on the spring. This is called the motion ratio...the differential distance of the pivot of the lever to the center of the spring, and must be taken into account along with the compressed height and the spring angle from vertical when picking a spring.

Does this help ...or possible confuse you more?

 

[TomO]

Hmmm. I need to give that one some thought.

 

[Fathead Racing]

Smarts

Jeeze dq. You just blew your image! How could a guy with a big meaty arm with a tatoo of Rat Fink on it have a brain too: : : Now I have to go back and reread all your posts and pay more attention

 

[SS425HP]

spring

I say " HUH?"

 

[dq409]

Reply #2,,,,,

Yes,for a drag racing application, the lighter (283) springs would allow more energy stored for frontal lift.
The limitations become the actual front suspension travel.
If your limited mechanically to a dinension at full travel(check without the springs installed), then the stored rate of de-compression is effected by the total weight transfer of the vehicle.
Traction and center of gravity can negate any "lift"benifit.
After about 300',you really don't need the nose "in the air" as frontal area can/will slow you even more than the 60' increase.

Hey Fat,,,I didn`t know you could read? i thought you just looked at the pictures,,,Thats why I post so many,,,Heeeeheeee

 

[Bungy]

I think it all depends on how much the springs are compressed once they are installed in the car. Since the 283 springs are almost 2" taller they would be the ones you want to use even though they have a lesser rate, because they would be compressed more giving you more "push" up off the line. But it all depends on the height they are installed at. If the springs were the same free height then the 409 ones would be the way to go.
If you want a 100% sure answer just install both and check your 60ft times. That's easy, isn't it?

 

[posi857]

Eaton Springs - an excellent resource for any spring question. Try their tech page or e-mail Mike.

http://www.eatonsprings.com/tech infro.htm

Posi

 

[CDNpontiac409guy]

HAH !
DQ... that was PERFECT !!!!
This is weird... The number that seems to be missing is a 6004. This is the actual big block spring. WAY bigger wire than the 6000, but about the same free length. The 658A is THE perfect spring for firm handling and correct ride height in a small block car... or a really light big block car ( such as a 61-62 2dr sdn with a no accessories ).

All in all, the 6004 spring installed, with the car at ride height, supports almost 200 pounds more than the other part numbers.
This is the one that I've been using for about 17 years.

 

[dq409]

Oz, I went to the spring shop today and got the lowdown.
We`re both right !
The 6004 is the standard spring listed as small block application with the 6000 being the 2 door sedan listing (lighter).
The 658a is listed as the 409 or HD small block application.
So there is sill no doubt that your right as always !! LOL ! Never doubted you but was checking on getting them local and the 658a number threw me off.
So now I will check what springs I have in the rear now as I have those specs also.
If they don`t measure right I`ll go with the 6004 and cut one coil.

They also show a 6003 for the rear but no specs in the book,,,GO figure !!
Thanks again for your expertise !! ,,,,dq

 

[dq409]

Reply # 3,,,,This is a good one to figure your hieght,,,dq

Right on!
And the spring rate in these specifications (324 and 403) are actually pounds of weight needed to compress the spring one inch. That's the first inch. The second inch of compression takes an additional (324 lbs and 403 lbs) and the third inch needs another (324 and 403). Since the ride height of these springs is not given, (typically 11 inches) you have to do some math. (keep in mind that the lower control arm is giving your car's weight a 2:1 advantage over the spring)
If ride height is 11" and the spring's free height is 18.78", to get the 11 inch ride height, the spring must be compressed 7.78". Multiply 7.78" times 324 lbs to get 2520.72 lbs. That would mean you could achieve an 11 inch ride height with these springs if your car weighs 2520.72 lbs on the front end.
Going the other way, 2263 divided by 324 = 6.78" so 18.78-6.78=12" so the 283 springs would give you a 12" ride height with 2263 lbs of sprung weight on the front of your car.
283 spring: wire size .672,,standing hgt. 18.78"
load 2263#,,,rate load hgt.324

409 spring: wire size .690,,,standing hgt. 16.893"
load 2052#,,,rate load hgt. 403

You can measure your car's ride height with a tape measure thru the center of the spring from end to end with the weight of the car setting on the tires.

Steve

 

[Gerry]

Coil springs

DQ. If you look in the assembly manual for your year vehicle, you can find the G. M. part number for the correct coil spring based on the options (RPO) your vehicle was equipped with from the factory. In the back of the Moog Coil Spring catalog there is a section to cross reference the G.M. part number to a Moog number. Most of the part numbers are still available.

 

[dq409]

Gerry,,Thanks ,,I have those numbers. The reason I wanted to know about the spring specs is so I can determine what spring is installed now and options to change to. Like ride hieght and maybe a better spring for launching.
Getting the right factory spring is the easy part,,,,,,dq