spring rate is simply the amount of force in KG it takes to compress the spring 1mm. The stock spring is generally about right. The sag is the important setting. With the bike on a stand, measure from axle center to seat bolt & record it. Then sit on the bike with your riding gear on and measures again from the same spots. The difference is called the "sag". Because it's progressive system, having the right sag is very important. At the top of the shock spring you will see two treaded rings with slots on the outside. The one closes to the spring is the adjuster and the other is a lock ring to keep the adjuster from moving. With the bike on a stand, using a long punch and hammer, tap the top ring to move it CCW the do the same for the adjuster ring, tapping it CW. Do about 2 turns then sit on the bike again to check the "sag". Keep doing this until the sag is 4". When dont, tighten the top ring CW to hlod the adjuster in place. Hope this helps. Cam.