R1 (Free Sag): Measure from a fixed point on the bike (e.g., axle to tail) with the bike on a stand (suspension fully extended).
R2 (Static Sag): Measure the same points with the bike on the ground, off the stand, with no rider.
R3 (Rider Sag): Measure the same points with the rider fully geared on the bike, in riding position.
Standard Ranges (approx):
Static: 10-25mm | Rider: 25-35mm