Easily Check Your Chain's Wear

September 03, 2015

Inspecting your chain regularly and replacing when necessary is important to ensure that you get the best performance from your drivetrain and save on running costs in the long run.

Through usage, the rollers and pins in the chain wear and make the gaps between them larger, effectively making the chain longer. While it's not technically "stretching," the chain length is actually lengthening. This wears the cassette by making the scallops on the cogs deeper or larger causing chain and cassette not to mesh correctly.

Checking the chain is simple and will take about 15 seconds of your time, using a tool such as the BBB Chain Checker which is of minimal cost. You need to insert the chain checker 2-3 times around the chain to ensure the reading is correct. The results of the are:

Below 75% - your chain is in good health and nothing needs to be done.
Between 75% and up to 100% - your chain will need replaced. At this level of wear it is not necessary to replace the cassette.
At 100% - You will need to replace both the cassette and chain. The chain has worn so much as to also wear out the cassette. It’s important to note that if you only replace the chain at this stage, without replacing the cassette, your gears will skip and it'll probably ride worse than it did before.
Beyond 100% - At this stage you will need to not only replace both the cassette and chain, but also inspect the front chainrings for wear as those probably need replacing as well.

Here's what different wear looks like.

Brand new chain. Chain checker doesn't fall in the chain at all...