Each of those little links has a roller that wears over time. As they wear the chain stretches. The simplest way to check for wear is the stretch test. Put the chain on your big chain ring. Grasp the it with your thumb and forefinger and pull it forward. If the chain is good, you should not be able to pull it far at all. If it’s worn, you’ll be able to pull it almost clear of the teeth.
Bike mechanics have a special tool to measure chain wear. If you’re not sure about the state of your chain, take it to your bike shop and ask them to have a look. You need specialist tools to fit a new chain, so this is definitely a job for a bike mechanic.
You can keep riding with a worn chain, but you risk damaging the teeth on your gear sprockets. As the chain starts to slip, it puts pressure on the front of the tooth and gradually wears it away. Instead of an even scallop, with a flat-topped tooth, you’ll end up with long slope on one side with sharp teeth. Replacing your chain as soon as you become aware that it’s wearing will keep your gear sprockets going longer.
Some schools of thought say you should replace chain and sprocket cluster at the same time. It’s not always necessary. So long as your gears are still in reasonable condition you can run a new chain with them.
How far will a chain go? That depends on the type of gear you have on your bike. Top of the line equipment naturally lasts a lot longer than the lower end of the range. It also depends how well you take care of your chain. If you clean and lubricate it regularly, it will last longer.
At the lower end of the equipment range, you’re probably looking at between 2 and 3,000 km for a chain. At the upper end you might get around 8,000 km from a chain. It’s a good idea to make a note of when you replace items on your bike, so you have some idea how far components can go.
See you on the road soon, God willing. Eddie Barkla
First published in the Bendigo Weekly Friday 15 September 2006