Spring Calc

Spring Rate Calculator


Enter your input parameters and click "Submit" to calculate your spring rate, or "Reset" to start over.

  • Total Riding Weight (pounds): includes the rider and anything else additional; e.g., hydration backpack, spare tube/tools, etc.
  • Rear Weight Bias (percent): the standard formula is based on a 60:40, rear-to-front total weight distribution. A more accurate way would be to use a bathroom scale under the rear wheel and a 2x4 under the front wheel, to determine the true sprung weight at the rear wheel. Position your body according to your riding style, and then enter this value for your total weight. Note that the default weight bias is sixty (60) %. Alternatively, you can use 55% for X-Country, 65% for Freeride, and 70% for Downhill.
  • Rear Wheel Travel (inches)
  • Shock Stroke (inches)
  • Shock Sag (percentage of shock stroke): the standard formula uses the Fox Racing Shox-recommended 25% of shock stroke. A zero-preload spring rate is determined, then preload is applied to calculate the corresponding sag. Choose a sag appropriate to your riding style. If you are an extreme rider (jumps, drops, big hits, etc.) you should run less sag and a correspondingly higher spring rate.
  • Preload Adjuster (number of turns): a minimum of 1.0 is required.
  • End-Coil Effect (percent): closed/ground compression springs have a typically lower spring rate in their initial deflection range. The canned value is a best guess of the effect ECE will have on preload adjustment. It is a percentage of the overall spring rate used in calculating the spring tension for the specified turns of preload.

Input Parameters

Total Riding Weight (lbs)
Rear Weight Bias (%)
Rear Wheel Travel (in)
Shock Stroke (in)
Shock Sag (%)
Preload Adjuster (n.n)
End Coil Effect (%)

Output Parameters

Leverage Ratio (Travel/Stroke)
Calculated Spring Rate (lbs/in)
Suggested Spring Rate (lbs/in)
Suggested Spring Rate Preloaded Sag (%)

Optional Spring Rates

Spring Rate (lbs) Shock Sag (%) Shock Sag (in)
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