One of our specialties is offering custom spring rate options on our coilovers. We often see requests for spring rates in both KG/mm and LB/in. All of our springs will be based off the KG/mm scaling, so we put together a handy chart here to help you convert over your spring rates from the standard scaling.
Springs are rated in kilograms per millimeter (KG/mm) or pounds per inch (lb/in), which represents the amount of force required to compress the spring 1 MM at its fully extended length. A spring rated at 12 KG/mm will compress 1 MM for every 12 KG of force exerted on the spring. Compressing the spring 2 MM would take 24 KG pounds of force with a linear spring. Conversely on the LB/in scale, it is the amount of force required to compress the spring 1 inch at it's fully extended length.