The best way to determine whether a chain is worn is by measuring its length. A new half inch pitch chain will have a pin at exactly every half inch. As the pins and sleeves wear, this spacing increases, concentrating more load on the last tooth of engagement as the chain rolls off the sprocket, thus changing the tooth profile. When chain pitch grows over one half percent, it is time for a new chain. At one percent, sprocket wear progresses rapidly because this length change occurs only between pin and sleeve so that it is concentrated on every second pitch; the pitch of the inner link containing the rollers remaining constant. By holding a ruler along the chain on the bicycle, align an inch mark with a pin and see how far off the mark the pin is at twelve inches. An eighth of an inch (0.125) is one percent, twice the sixteenth limit that is a prudent time for a new chain.