I've heard that the old process of using static (unloaded) sag to determine rear spring rate is changing. The new process uses actual spring preload in millimeters to help make the decision and goes like this;
1) Set race sag as usual
2) Measure spring preload
3) If preload is between 2 to 8mm spring is probably good (2mm being more on the stiff side, etc)
4) Less than 2mm spring is too stiff, more than 8 and it's too soft.
Heck, 2 mm is practically nothing. Most springs will almost rattle on the perches at that setting but that's the new trend, even if it means your unloaded sag is huge (45-70mm!). I tried it on my bike and it made a huge difference in my spring selection, from 4.5 to 6.0. Wow! And it worked much better to boot. Obviously, this process favors stiffer rates everything else being equal.
Anyway, just curious what others think about this.
Retired Mechanical Engineer, published technical writer, MSC Engineering, Instagram @maxvonauto
