https://davidharuch.github.io/MTB-Spring-Calc/LRspring.html

I was tired of hearing "what coil weight should I get", and existing spring calcs aren't too good. Manufacturer ones don't let you put in custom parts either :-(. So I made my own in javascript with a website gui.

The more people that use it and give feedback to me the better it will get because I can update my models! If you use it please send me a screenshot of your inputs, your bike brand/model and size, and any measurements you've made like % sag, sprung/unsprung weights, etc...

It is already much more advanced than most free calculators as for as I know

Another good one is https://thesuspensionlab.nz/coil-spring-calculator-beta

• Bike sprung/unsprung mass estimation
• Damper gas Force included
• Non-constant leverage ratio curves
• Outputs of sag, natural frequency, bottom out force, bottom out energy instead of just sag

• metric & imperial unit input options

• Nonlinear bottom out energy computation

• Sprung/unsprung overrides

• Nonlinear leverage ratio input

• Graphical plotting of force/displacement, spring rate/displacement, etc...

• Air shock comparission for reference from dyno/spring data

• % Sag (and therefore spring) recommendations based on riding style, track speed/steepness, and desired suspension feel

• Incorporate leverage ratio of the specific bike into the recommendations