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 Post subject: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 9:13 am 
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Location: North Carolina
I have 12" tall 110 lb springs on my 4 link dragster with BBC and aluminum heads. When I get the everything adjusted, the coils are compressed 4" on each side. That equates to 880 lbs to compress both coils 4".

This seems to me that the springs are compressed too much. I am wondering if I need to go to 130# springs on the rear. That is the next spring that is stiffer than the 110# spring.

John

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 Post subject: Re: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 9:25 am 
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It does sound like they are compressed too much to me. Hyper coil list a 125#. I take it your shocks are in front of the axle because as light as that car should be it shouldn't need that much spring otherwise.

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 Post subject: Re: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 10:55 am 
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gearhead1011 wrote:
It does sound like they are compressed too much to me. Hyper coil list a 125#. I take it your shocks are in front of the axle because as light as that car should be it shouldn't need that much spring otherwise.


Chuck:
The shocks are located behind the rear axle. The only weight I have added has been a Moroso accumulator and the B&M Fluid Consistency tank. This is a shot with the 110# springs below.


Image

When I installed the 130# springs they compressed 3.125". That comes out to 812.5 lbs.

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 Post subject: Re: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 12:35 pm 
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Call S&W........... =;

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 Post subject: Re: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 12:40 pm 
 
Ya that sounds like it is way to much spring for a dragster.


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 Post subject: Re: Coil Over Springs
 Post Posted: Tue Apr 14, 2009 1:05 pm 
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Beretta wrote:
Call S&W........... =;


Barry:
I did. They were the ones that sent the 130# springs. They did not have an explanation either.

Image

This shot is with the 130# springs. It seems that the 125# spring is the most common. So I guess the 130# spring will work out.

John

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 Post subject: Re: Coil Over Springs
 Post Posted: Thu Apr 16, 2009 7:28 pm 
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Location: coming at ya
A couple different 4-link dragsters i've had,
97Undercover 95lbs
2000 Racecraft 125lbs
2002 Racecraft 110lbs
2008 Mullis swingarm single 550 lbs

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 Post subject: Re: Coil Over Springs
 Post Posted: Sat Apr 18, 2009 1:00 am 
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oobob wrote:
A couple different 4-link dragsters i've had,
97Undercover 95lbs
2000 Racecraft 125lbs
2002 Racecraft 110lbs
2008 Mullis swingarm single 550 lbs


Mark:
Thanks for the input. We tried the car tonight. I can't tell any difference between the two springs. All the numbers stayed the same. It doesn't ride any rougher.

John

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 Post subject: Re: Coil Over Springs
 Post Posted: Sat Apr 18, 2009 9:55 am 
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John, You have to remember that with spring being behind Axle the compressed weight won't be the same as real rear weight. When the spring shows 880lbs if it was above the axle it would be a little different. If the spring was in front of the axle, it would be different yet. How much it is compressed to hold that corners weight is not as important as is there enough travel both compression and separation. The bottoming or topping out shows a spring too low in rate. I believe in stiffer rates, comparatively for a smooth track surface, because it adds stability, just because there is less movement. You also know it's too much rate if your distorting side wall enough to ruin contact patch, but this also depends on IC. Too low an IC can make the effective spring rate seem like a less rated spring. (It lost some help from anti-squat values. You can add to effective spring rate by just raising the IC a little. You can do this in between holes with small ride height adjustments. Example, if you raise rear height, it raises COG some but it raises IC more, so it narrows the relationship of the GOG and the IC. This gives more anti-squat value, therefore making effective spring rate seem stiffer. This is why I say springs/ shocks and IC's are pardners.

I forgot to add, if you lower chassis to eliminate some weight transfer it lowers the IC more than the COG, so you need to reset IC's.

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 Post subject: Re: Coil Over Springs
 Post Posted: Sat Apr 18, 2009 6:03 pm 
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Bubstr wrote:
John, You have to remember that with spring being behind Axle the compressed weight won't be the same as real rear weight. When the spring shows 880lbs if it was above the axle it would be a little different. If the spring was in front of the axle, it would be different yet. How much it is compressed to hold that corners weight is not as important as is there enough travel both compression and separation. The bottoming or topping out shows a spring too low in rate. I believe in stiffer rates, comparatively for a smooth track surface, because it adds stability, just because there is less movement. You also know it's too much rate if your distorting side wall enough to ruin contact patch, but this also depends on IC. Too low an IC can make the effective spring rate seem like a less rated spring. (It lost some help from anti-squat values. You can add to effective spring rate by just raising the IC a little. You can do this in between holes with small ride height adjustments. Example, if you raise rear height, it raises COG some but it raises IC more, so it narrows the relationship of the GOG and the IC. This gives more anti-squat value, therefore making effective spring rate seem stiffer. This is why I say springs/ shocks and IC's are pardners.

I forgot to add, if you lower chassis to eliminate some weight transfer it lowers the IC more than the COG, so you need to reset IC's.


Bubstr:
The shocks are set at 13.5" center to center distance. That is what the S&W manual says. I just had a problem looking at the 12" tall 110 lb. springs and seeing them compress 4".

Years ago I built round track suspensions with truck trailing arms and I tried the springs in front of the axle and on top of the axle. I have probably forgotten more than I will ever remember. I just haven't worked with it enough over the last few years. I guess I will have to get out the books and study some more. When I let my partner drive the car I stand there and watch how the tires and rear suspension work.


Thanks for your input. I appreciate it.

John

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 Post subject: Re: Coil Over Springs
 Post Posted: Sun Apr 19, 2009 7:26 am 
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Dennis, A dragster is a hole different ball game as far as set up....

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 Post subject: Re: Coil Over Springs
 Post Posted: Sun Apr 19, 2009 3:16 pm 
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Beretta wrote:
Dennis, A dragster is a hole different ball game as far as set up....


What is different, other than some have droop built in, a longer WB and all have a certain amount of flex?

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