Shock / Fork Spring Rate Calculator
If you have ever wanted to be able to determine what strength springs are on your bike you can use this information to help you figure it out. You'll need to be able to measure the spring by itself. That means it has to be removed from the shock or forks. The three measurements you need from your spring are:
Wire diameter - the diameter of the wire used to make the spring.
Coil diameter - the outer diameter of the coil.
Number of coils - the number of free coils. It can be a fractional amount.
All dimensions in decimal inches. The default values are a 89 yz250 front fork
Related Spring Tips and Notes
"To count free coils this is what I do. Do not count the coil at each end that is flatened and really used for seating. starting where the spring "takes off" from the base coil, I count full coils from this point on, and then do my best guess as to fraction of coil before returning to the base coil at the other end. Basicly once the free coils touch the base coil, the spring is done. The base coil can't provide any springing, and thus isn't free." mtiberio
"Why doesn't the number of coils per inch come into play? If you have ever looked at a progressive spring, you'll find that one end has the coils closer together than the other. The rate is constant across the spring reguardless of the coil spacing. What happens is once you begin to use the spring, the coils that are close together finally touch (coil bind) reducing the number of free coils, (making the denomenator smaller in the equation) and increasing the spring rate for the remaining unbound coils." mtiberio