Springs are the foundation from which we build ideal suspension performance. It is the correct spring rate combined with the correct amount of preload that creates our ride height. After we have that, we can then set about ensuring that our springs then compress and rebound at the correct rate (damping). You will require heavier springs for your weight.
Terry, When going to stiffer springs, do you always plan on adding more rebound damping? When going to stiffer fork springs, would you start with a lower fork oil height? Thanks, those are two things I have been wondering about. Tim
When installing stiffer springs I'm always looking at the necessity of adjusting damping. If the standard spring rates were insufficient for a riders weight then generally the damping wouldn't be suitable either. The air gap adds a progressiveness to the overall feel. The standard gap should work fine with the heavier spring. Changing the air gap will create a different feel at the end of the stroke. More or less could be more suitable for you and your personal preference. Try removing 10ml of oil from each leg. Ride for a few laps and note the change. Replace the oil and again note the difference. Now add an extra 10ml. This is a simple experiment that will yield a greater understanding of the air spring effect. If you use a syringe you can add the oil through the bleed screws making the process so simple.
Kg/mm is relating to force over distance where psi is pressure over area. If you have a .43kgmm spring with 320mm of travel simply multiply the rate by the distance to give you total force. If you wish to convert kg/mm to lbs/inch simply multiply by 55.88
Is there a general rule of thumb on loaded sag in mm for forks which can give a general idea of which way to go on spring rates +- for a given sag. I know that there are plenty of web sites which can give reccommendations but was also wondering about using the loaded sag as a guideline. On CRF Showa forks when they give a recommendation for spring rates say a .49kg, is that factoring in the inner chamber spring rate also or do you take the recommended rate and subtract the ICS(if so, what would the rate be) to give you the rate you need.