Yes, your chain wears out.stefpap
Does this sound familiar?
What’s wrong with your bike?
We’ve all had at least one of those experiences as cyclists. A properly functioning drivetrain is one of those things we tend to take for granted. You shift gears and expect your bike to do as told. Every so often though, things don’t work as advertised.
The first step is making sure the “simple” things are taken care of. Make sure you’ve had your shifters and derailleurs properly adjusted. Then take a look to make sure nothing is clearly broken and that you don’t have a stick or other debris caught in your drivetrain.
If you’ve taken care of these basics, there’s a good chance that your problems are cause by a worn out chain.
Good shifting and pedaling depends on your chain doing two things properly. First, the chain needs to be able to move left and right between gears as you shift. In order to do this, the chain needs to be able to flex a small amount.
As your chain ages, this small amount of flex becomes a big amount of flex. Eventually, the flex is so great that your derailleur tries to pull or push the chain onto a new gear but the worn chain stays put. It simply wiggles between the last gear you were in and where your derailleur is trying to pull it, all without ever actually changing gears.
Take a look at the two chains pictured next to each other to see an example of how much more a worn chain will flex.
Measuring Chain Wear
It’s pretty easy to see how an overly flexible chain will lead to shift issues. Measuring and properly quantifying this flex while a chain is installed on a bike isn’t quite as easy. Fortunately, there is a simple way to measure chain wear using a tool that measures the wear of the small bushings that surround the pins on each link.
You can see the tool being used on a new chain and an old chain in the pictures above. The numbers on the tool are measuring the percentage (0-1%) growth in the distance between subsequent bushings. All multi-speed bikes use chains with the same distance between each link. Due to manufacturing imperfections and the lubricant that is applied to chains, this distance between links will vary between 100 – 100.5% of the initial design.
As a chain is used, these bushings rotate against the gears on a bike. This friction, combined with additional grinding caused by everyday grit & grime, causes the bushings to wear down. Eventually, the distance between them exceeds 100.75% of the original distance between new bushings. This growth is what is commonly referred to as “chain stretch”.
Chains should be replaced when the measured chain stretch is between 0.75 – 0.95%. Once a chain is 1% or more elongated the bushings have also likely worn many, if not all, of the gears on a bicycle as well. Unfortunately, in these situations, installing a new chain will often cause even more problems. A new chain will not mesh snugly on worn gears and the bike will have shifting problems until all the gears are replaced.
The Good News
For most cyclists, the good news is chains will typically last you quite some time. Enthusiasts and competitive riders might need to replace their chains 1-2 times a season, especially on high-mileage road bikes. In general, you should expect a new chain to last somewhere between 1500 – 3000 miles on pavement and 1000+ miles off-road. Always remember, is a free service – and a new chain is ALWAYS cheaper than replacing an entire drivetrain.
Keep on top of your regular bicycle maintenance and you’ll be a happier, better and richer rider.