A bicycle chain works hard and under really miserable conditions: Dirt, moisture and mechanical load take their toll on each of the more than one hundred moving links. Ideally, it would run in a closed oil bath. But this is not feasible on a bicycle. Regular lubrication is therefore the only sensible way to maintain flawless function, extend the service life of the drive and avoid annoying background noise. Wear is mainly caused by the tensile load of the crank drive on the roller in the chain link, which rotates on the rivet pin. When it engages with the sprocket, this translates the force of the crank from horizontal to vertical. In the process, metal grinds against metal and the material abrasion causes the chain links to inevitably become slightly longer. Chain links that have become too long no longer fit exactly between the individual sprocket teeth, removing material and destroying the sprockets and chainrings. This cannot be prevented.
However, good lubrication can keep wear in check - as long as sufficient lubricant gets between the metal components in every load situation to permanently minimise friction. However, this only works if existing dirt particles do not combine with the oil to form an abrasive paste. As oil has good creeping properties, it also draws dirt particles between the components of the chain. This means that oil on a dirty chain increases wear instead of minimising it.
This is why it is so important to thoroughly clean the chain and the parts of the drive it passes through before lubricating. Hub or gear systems with a chain drive also require regular lubrication. However, with derailleur gears, wear is significantly higher due to the chain skew when shifting via the sprocket cassette and various chainrings. Powerful mid-drive motors increase chain wear on e-bikes even more.
