How to avoid chain stretch
One of the most common problems that comes into our workshop is issues with shifting or chain skipping. Chain skipping is when the pedals slip forward as pressure is applied resulting in a sudden jerk forward of the feet. One cause of chain skipping is a stretched chain. Believe it or not, bicycle chains actually stretch! A stretched chain will wear down the sprockets causing them to become sharp. The teeth then have less to grip the chain with and under load can lose the chain causing chain skipping. There is no way to repair a stretched chain you can only replace it.
Keep you chain well lubed. Shifting gears puts a lot of strain on the chain. Give your chain a head start by allowing each link to move freely.
Ride your bike with a straight chain line. The picture below shows a bent chain line. You can see the rear derailleur is set to the easiest gears (to the left) and the front derailleur is set to the hardest gears (to the right). This results in the chain running slightly bent which over time stretches the chain.
By riding in a straight chain line, as pictured below, the life of the chain is lengthened.
Don’t put too much pressure on the pedals when changing gear. This is particularly common when cycling up hill! Try to change down the gears before you hit the hill so there is less pressure on the chain when you shift.