The elongation of a chain during use relates to the wear of the contact surfaces between the pin and the bush. This is why it is of vital importance to always keep the chain well lubricated, since lubrication is the only way to reduce friction and therefore the wear of the components. The initial elongation after the installation of a new chain is physiological and is due to the settling of the chain-gear wheel-sprocket system. In some cases the chain may stretch unevenly, that is, it stretches only in a section. This situation can be seen by observing the lower part of the chain (section that is not stretched) while the rear wheels are turned: if the lower section oscillates periodically at each turn of the chain, this means that there is an elongated section (obviously after excluding wear of the gear wheel teeth and sprocket). In this case, the cause of the non-homogeneous elongation is an incorrect tightening of the chain which has led to an overstress that plastically deforms the components in the section between the gear wheel and sprocket. N.B. For correct maintenance of the chain and entire transmission, see our article “How to do it – Correct maintenance of the chain, gear wheel and sprocket“.
