Fork Spring Weights

Go with Fredette's recommendations, especially if you ride tighter trails and your forks have stock valving.

Jeff has been involved with KDXs for well over 20 years, whereas RT's guide is based on generic formulas for rider weight, bike weight and riding conditions. It is probably biased toward MX riding and bikes that have less high speed compression damping than the KDX. If you use the RT recommended 0.42 springs, your bike will probably be harsher on rocks and roots, but may handle triple jumps better than Fredette's recommendations.

Here's one vote for the stiffer springs, maybe .40, but not .38. Go with the rate of springs that will hold the bike up properly with a modest amount of preload on the springs (10mm), not the 25 -40 (whatever it is) that comes stock.

Don't try to fix the valving with incorrect rate springs. If the valving is not like you like it, then change it, but put in the correct rate springs to hold up the weight of the bike and rider.

A fairly generic formula IS all that is needed on the forks, as no linkage is involved. Read the article on the Race Tech site which mentions 25% sag in the front and 33% in the rear.