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[QUOTE="James Dean, post: 24442, member: 18501"]
Many dimensions go into the design of a spring. The spring "rate" is very sensitive to wire size and overall diameter.

Here is the equation:

Spring rate K= Gd**4/8nD**3

K is the stiffness (lb/in)

G is the material elastic modulus

d is the wire size

n is the number of active coils

D is the mean coil diameter

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The wire size (d) and coil diameter (D) are by far more sensitive than the number of coils. By several orders of magnitude.

The reliability of the spring not to sack out over time or break in two may be the tradeoff here.

This equation can be used for the fork, shock, or clutch springs when making changes.

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For the lightest possible bike we really should be looking for the fewest number of coils to reduce weight. The Engineers have left an extra pound or two on your shock spring that could be trimmed off just for the sake of reliability.

I used this equation once to drop a pound off my KX by using an RM spring. Fewer coils and a smaller wire size offset each other to make a lighter spring with the same stiffness. It fit perfectly and never had a problem.  [img]http://dirtrider.net/ubb2/biggrin.gif[/img]

James Dean
[/QUOTE]

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