Sag is how much your machine settles on its suspension at rest. To measure the sag, have a helper lift the rear of the bike as high as possible—if you have a centerstand, just use that to lift the rear wheel off the ground. Now measure from the rear axle to a reference point straight above—the seat, fender, etc. Do the same with the front suspension. This measurement is the suspension value with zero sag—for our example, let’s say the number was about ten inches (250mm). This measurement is called unloaded or free sag.