Need a softer front coil spring. - Team Camaro Tech
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post #1 of 12 (permalink) Old Jul 25th, 10, 07:37 PM Thread Starter
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Need a softer front coil spring.

I'm looking for a softer front coil spring. I currently have Moog 6320's. I'm happy with the ride height but they are way to stiff. The front of car will not push down even than an inch when pushing down on the braces that run from the fender to the radiator support. This is without any shocks installed. And the Hotchkis swaybar very loose on the ends.

I would like a spring with the same ride height but would allow more suspension travel. I have looked at the chart that Mr. Pozzi has posted and I'm a little confused as to how to read it. There's not much choice if you stay with the OE spring I.D.

Small block with alum. heads, no A/C, Has 4 spd, P/S, alum. radiator, cowl hood. D368s.

Suggestions? Dave are you out there?

Dave

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Last edited by Fred Mertz; Jul 25th, 10 at 08:03 PM.
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post #2 of 12 (permalink) Old Jul 26th, 10, 09:39 AM
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Re: Need a softer front coil spring.

I do not know too much about the specific springs available but here is a primeron spring basics that might help with the chart:

Springs are largely classified by their 'K constant", which tells how much deflection a spring will incur at a given force. So take a spring with a K constant = 327 lbs/inch (approx K of the stock springs). If you rest 327 lbs on it it will depress 1". 654 lbs it will deflect 2" and so on. it is linear.

The K constant is largely determined by the material type (diffrent steels), diameter of wire and diferent # of coils. So I am not sure how many diffeent flavors there are since the only logical change the modify K is the diameter of the wire. # coild would effect total travel.

P. Boggs

Last edited by ramblin67rs; Jul 26th, 10 at 09:40 AM. Reason: add (approx K of the stock springs)
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post #3 of 12 (permalink) Old Jul 26th, 10, 09:43 AM
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Re: Need a softer front coil spring.

according to DAve's info the Moogs have a k of approx 650 in/lbs, which is 2x the stock springs. not sure if this helps

P. Boggs
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post #4 of 12 (permalink) Old Jul 26th, 10, 09:56 AM
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Re: Need a softer front coil spring.

http://pozziracing.com/Media/spring_chart.jpg

This should help.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #5 of 12 (permalink) Old Jul 26th, 10, 10:19 AM
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Re: Need a softer front coil spring.

The springs unless they lower the ride height won't limit suspension travel. Dave your 6320's have a spring rate of 380 lbs/inch and stock springs are about 325 lbs/inch. The Hotchkis 2" drop springs I'm using have a spring rate of 600 lbs/inch...

Quote:
Originally Posted by davidpozzi View Post
6308 and 6320 are the two best stock replacement springs for a very streetable camaro where a stock ride rate is desired. They both are 380 lbs/inch, lower perf stock coils are 325.

I think the 6320 is about 3/4" higher ride height, the 6308......
David

I have no ride issues with the 600 lbs/inch and Koni shocks. I can't say this enough shocks control the springs and if you don't have the right shocks it will cause problems... Wheels and tires are also a big contributor to ride quality. The best suspension in the world won't help if you have crappy tires and wheels... At one point I switched from BFG's to Dunlop's and the ride quality was far better with the Dunlops. Later I changed to 17" alum wheels and 45 series tires and the ride quality again was improved over 15" steel wheels and 60 series tires!

I'm not saying to bail on ralleys and tall sidewalls, just pointing out there are a lot of other areas that come into play, it's not just springs...

I really can't imagine 380 lb/inch springs as the cause of too stiff ride... Dave maybe something else is interfearing with the suspension making it hard to bounce with the shocks loose or possibly you have different (stiffer) springs than you think... Using the fender braces I can bounce my front end with the shocks in place no problem and that's with 600 lbs/inch springs...

...Dennis

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post #6 of 12 (permalink) Old Jul 26th, 10, 11:59 AM
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Smile Re: Need a softer front coil spring.

Quote:
Originally Posted by DjD View Post
Later I changed to 17" alum wheels and 45 series tires and the ride quality again was improved over 15" steel wheels and 60 series tires!
I find this hard to believe ! I understand your reasoning on the other stuff.

I would like a comparison, with the same tire brand and wheel type.

Bigger wheels usually means a stiffer side wall tire, which means a rougher ride.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #7 of 12 (permalink) Old Jul 26th, 10, 12:24 PM
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Re: Need a softer front coil spring.

Quote:
Originally Posted by TJS69 View Post
I find this hard to believe ! I understand your reasoning on the other stuff.

I would like a comparison, with the same tire brand and wheel type.

Bigger wheels usually means a stiffer side wall tire, which means a rougher ride.
It's simple, alum wheels vs steel; steel are far more rigid and the large sidewall can't make up for that. Add modern tire design which almost anything 14" or 15" can't keep up with because design is at least 20 years old.

Look at all your new luxury (looking at ride quality) cars and you'll find 18" - 20" wheels and small sidewalls. Modern suspensions obviously help but if they could get an even better ride with steel and big sidewalls new cars would come with them...

And as I have shared over and over, I got to experience ride and performance changes one part at a time as I kept the car driveable and could not afford to make more than one change at a time...

...Dennis

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post #8 of 12 (permalink) Old Jul 26th, 10, 09:13 PM Thread Starter
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Re: Need a softer front coil spring.

Tom,

The chart you posted is the one I'm trying to make sense off. How much smaller or larger in coil I.D. can I go without causing more problems?

Dave

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post #9 of 12 (permalink) Old Jul 27th, 10, 05:02 AM
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Re: Need a softer front coil spring.

You're looking for a spring with a mean coil diameter that fits in your spring perches. The ID of the spring doesn't change much with the diameter of the wire.

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
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post #10 of 12 (permalink) Old Jul 27th, 10, 09:17 AM
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Smile Re: Need a softer front coil spring.

I have Hotchkis front coils that have the 600lb rate ! Is something bound up not giving you any travel ? Do the springs compress when you lift the car on a floor jack, under a lower control arm ? I always raise my car, right under the shock mounts, and the spring compresses.

69 Camaro -originally a LM1 car. 327, Edelbrock E-streets, hooker, DUI performance distributors, ultradyne cam, stewart, TRW etc. Vintage Air, AGR steering, Corbeau GTSII seats, 700R4 transmission, 12-bolt w/Eaton 4.11:1
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post #11 of 12 (permalink) Old Jul 29th, 10, 07:09 AM
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Re: Need a softer front coil spring.

Hey Fred,

Not sure what you are asking about the I.D. of the spring....the I.D. is typically a fit function. One typically chooses an ID that physically fits the car. The two things that can be selected to modify the stiffness of a spring is the "Wire Diameter" and "Free Height" (length of spring unloaded). Changing the I.D. will not have much effect on the stiffness of the spring.


If you are looking for a softer spring, a simplified process an engineer would use when building a new car would be: determine what I.D. and "Free Height" will fit your car (or it needs). Then of those choose one with a lower "K" which is "Rate load hght" on his chart.

The "K" value is a unique property of the spring that is determined by the wire diameter, material type used (steel, Al, etc), number of coils, natural length, and a few others. SO if you choose one that fits on your car. You just need to worry about the "K" value selection

***If you need to determine the "K" of your current springs you can measure all of the critical values and plug them in to this chart


Good Luck

P. Boggs
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post #12 of 12 (permalink) Old Jul 29th, 10, 10:53 AM
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Re: Need a softer front coil spring.

Quote:
Originally Posted by ramblin67rs View Post
Hey Fred,

Changing the I.D. will not have much effect on the stiffness of the spring.



Changing the ID, OD, or mean diameter will make a large change in the stiffness of the spring. Note the D³ factor in the equation. In a nominal 4.5" diameter automotive coil spring, a 10% increase in diameter will result in about a 25% reduction in rate, and a 38% increase in rate for a reduction diameter of 10%.

"For those that will fight for it...FREEDOM ...has a flavor the protected shall never know."
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