Spring rate

Spring rate describes how stiff a fork or shock spring is: the force needed to compress it by a given distance, usually stated in N/mm or kg/mm. A linear spring has the same rate throughout its travel, while a progressive spring gets stiffer as it compresses.

The right rate depends mainly on rider weight with gear, plus luggage and riding style. With a spring that is too soft you need excessive preload to set sag, and the bike dives and bottoms out; too stiff and the bike rides harshly and loses grip on bumps.

A good check: set rider sag with preload, then measure static sag. If they cannot both be in the recommended range, change the spring rather than the damping. Suspension specialists and spring calculators help choose the correct rate.