Before we get into the details of tuning, first let's learn what all the suspension terminology means. Spring rate is how powerful the springs are. Stronger springs take additional energy to squeeze a specified amount. The more aggressive and heavier riders can benefit from stronger springs, but they additionally lessen the capacity to take up minor bumps. Springs, being springs, take extra energy to squeeze as they go, thus we have spring "rate." Any energy will begin to squeeze a spring, it is how much the energy is needed to boost per amount of movement that determines the rate.
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Progressive springs have varying spring rates and commonly seem to have the spring coils tighter together over a portion of the spring length. The spring coils that are tighter together are intended to be softer than the remainder. As soon as a impact comes along, they give way initially, until the spring coils connect against each other, and then the remainder of the spring coils, which are stronger, begin to squeeze. Hence, the springs can be stiff enough for more aggressive riding whilst still being able to take up lesser bumps smoothly.
Preload is how much spring energy the suspension has to maintain the bike and rider up. Back shocks generally have an exterior preload adjustment; forks are generally adjusted with spacers on top of the springs. With no preload, the suspension would collapse and would sag. Setting the preload too high, the suspension will be at it's full height, although the rider is sitting on the bike.. Primarily, preload ought to be set such that there is a little sag but not too much. Notice that preload does not raise spring rate, it just preloads the original force on the spring to move somewhere the bike sits on the "rate" scale.
Sag is a gauge of how much the suspension spring drops down when the rider is sitting on the bike. When going over holes, the wheels need to lengthen downwards to stay connected to the road. With no sag, even moving over minor bumps would let the wheels move off the road. This kills grip. A little sag is useful. Sag also consumes your suspension movement and this will lessen the capacity to take larger bumps with no bottoming. Too much sag is unacceptable. How much is correct? Lots of riders will offer you precise figures but the fact is that it has to be correct for you and, if you are a dedicated racer, this is not going to get condensed to a procedure. You merely have to attempt differing amounts until it feels appropriate.
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