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Author
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Topic: 600 lb. springs why waste your money?
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SundanceKid
Gearhead Posts: 853
From: UT
Registered: Feb 2001
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posted 02-03-2002 05:29 PM
   
I took some time today to measure the lbs./in on my stock 65 V8 springs. Heres the numbers I came up with.6.125 Active coils
5.0in. Coil diameter
.72in. Spring diameter
11,250,000 constant for spring steel
8 constant for coil springs 11,250,000 X .72 X .72 X .72 X .72 = 3023308.8
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8 X 6.125 X 5.0 X 5.0 X 5.0 = 6125 3023308.8 divided by 6125 = a 493.6 lb. spring
If you were to cut one coil off it would 6.125 to 5.125 or a 589.9 lb. spring if you were to cut 1.125 or 1 1/4 coils off it would be a 604 lb. spring
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Mpcoluv
Gearhead Posts: 799
From: Charlotte NC usa
Registered: Apr 2001
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posted 02-03-2002 10:22 PM
I agree completely. I wasted my money on a set of TMC 600 # springs. didn't lower the car, in fact raised it about 1". also the suspension seemed to be binding.
Bought a set of 428cj w/ac springs and cut a coil off, perfect! At least perfect for my 372C '69 coupe.
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SundanceKid
Gearhead Posts: 853
From: UT
Registered: Feb 2001
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posted 02-04-2002 11:17 PM
At least they don't cost 50.00 a piece like my race cars I've built! Has anyone tried those new variable rate springs yet?
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richard bohm
Gearhead Posts: 373
From: tucson,az-luray,va
Registered: May 2001
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posted 02-04-2002 11:29 PM
the only reasons to replace springs are:
1: the old ones are sagging and need replacing.
2: you need more spring rate for a heavier engine.
3: you are going racing and need more spring rate.
if you dont fall into one of these catagories you dont need to replace the front springs.
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Ryan Wilke
Gearhead Posts: 1078
From: Stanton, Michigan 49707
Registered: Oct 2000
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posted 02-08-2002 10:12 AM
quote:
Originally posted by Mpcoluv:
Bought a set of 428cj w/ac springs and cut a coil off, perfect! At least perfect for my 372C '69 coupe.
I assume your '69 Coupe is a street car?
I'm thinking that using cut 428 coils would result in some pretty hefty  spring rates - which wouldn't give you much weight transfer during a dragracing-style launch. I wonder what spring rate you'd get if you plugged in your cut 428 spring figures into SundanceKid's formula? SundanceKid:
That is a  formula...Thanks for sharing it! Typically, 6 cyl. coils (with a lesser spring rate) result in better launches (not lunches)  ------------------
The '3-Pedal Attitude' Kid
in a '69 FB w/ 306 now, but
the 460+ is coming... :D
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Fastback68
Gearhead Posts: 1315
From: Sucat, Paranaque, Philippines
Registered: Jul 99
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posted 02-08-2002 10:28 AM
Now HERE's a useless comment ... Sundance, one day when you were going on about E-code headlamps, I was impressed AND understood you, but this time I am totally in AWE! You are now tied for number 2 of people at M&M who I listen to when you talk. Engines .. well, it's still Alex, like everyone else 
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Mpcoluv
Gearhead Posts: 799
From: Charlotte NC usa
Registered: Apr 2001
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posted 02-08-2002 03:47 PM
quote:
Originally posted by Ryan Wilke:
I assume your '69 Coupe is a street car?
I'm thinking that using cut 428 coils would result in some pretty hefty spring rates - which wouldn't give you much weight transfer during a dragracing-style launch. I wonder what spring rate you'd get if you plugged in your cut 428 spring figures into SundanceKid's formula?SundanceKid:
I was going for the Trans Am stance not drag launches. You are right, 6 cylinder springs would be better for drag racing.
I think the rate is in the 525 range IIRC.
They are stiff but not as stiff as the 600# springs.
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SundanceKid
Gearhead Posts: 853
From: UT
Registered: Feb 2001
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posted 02-08-2002 06:59 PM
Fastback68, Thank you very much, that means alot to me. Now, you all know I didn't come up with that formula on my own right? I just take what I learn and adopt it to how it relates to me.
Heres a formula for leaf springs:2.50 width of springs
4 number of springs
.25 thickness of one leaf
53in. length of spring
12 constant for leaf springs (2.50 X 4) X (1000 X .25)3rd power
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( 12 ) X ( 60 ) =.83 X (4.17)3
or 60.17 lbs-in. approx Remember springs are linear so if the car goes beyond the springs "static state" it increases 60.17lbs. per inch so a three inch drop height from a static spring would be 60.17 X 3 or a 180.51 lb spring rate with the car resting fully on the wheels.
[This message has been edited by SundanceKid (edited 02-08-2002).]
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SundanceKid
Gearhead Posts: 853
From: UT
Registered: Feb 2001
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posted 02-08-2002 09:23 PM
Also, useing the leaf spring formula, it is more acurate to do each leaf individualy then to do the whole spring pack as a whole.
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