Mustang Coil Spring
Reference
Republished from http://www.2kgt.com/
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Choosing the right spring to give your steed that look and
performance you want can be quite a daunting task. On this page I
hope to bring you all the information you will need to make an
informed decision when you purchase lowering springs. Here you can
compare the performance and looks of various popular springs
available to the mustang community. If you have another spring or
would like to see another spring type here please email me at
chad@2kgt.com and I will be happy to track it down or post it on
this page. As always if you have any further questions I am always
available via email.
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Wheel Rates
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WR = Wheel Rate
SR = Spring Rate
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Wheel Rate is the amount of force the wheel is exerting on the
road. As you can see the wheel rate is a function of Spring Rate
and the Square of the Motion Ratio. On the mustangs Modified
McPherson Strut design the motion ratio is 0.5. When converting to
coil overs and making it a true McPherson strut the motion ratio is
closer to 0.9. Wheel Rate is expressed in lbs/in. Meaning if the
wheel rate were 400lb/in it would take 400lbs to compress 1
inch.
Motion ratio is important because it determines how effective
your springs are and how well your suspension is designed. By
running a few numbers you can quickly see how different spring
rates affect the Modified McPherson and true McPherson design. With
coilovers you can run a much less stiff spring and achieve much
higher wheel rates.
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Spring Rates
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Linear(Fixed)/Specific
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Spring Rate is the rate of which a spring will compress and
usually denoted in lbs/in (pounds per inch). That is to say it
takes x amount of force to compress the spring 1 inch. Say you
apply 100lbs of pressure to the spring and it compresses 1 inch,
then the spring rate would be 100lb/in. A linear spring will
continue in this fashion, you apply 200lbs and it should compress 2
inches. If it doesn't then you have a progressive rate spring. A
progressive spring rate is where the force required to compress the
spring changes as the spring is compressed. Below you can tell
which springs are progressive and which are linear. Progressive
rate springs will be denoted by having a range such as
500-560lb/in. A fixed rate spring will only have one number, such
as 650lb/in.
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K = Spring Constant (Spring Rate)
W = Spring Wire diameter (in)
G = 12,000,000 (constant for steel)
N = Active coil count + .5
D = Diameter of the spring as measured from the
center of the wire
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