The bicycle, at its essence, is a pretty simple machine. You push on the pedals, the cranks turn, the chain transfers that power to the rear wheel, the bike moves. S-i-m-p-l-e.

Breaking down any machine to its basics is a great way to identify what’s critical to its operation. Here we see that without the chain the bike doesn’t do what it’s designed to do: move. It makes sense, then, that we’d want to pay attention to the condition of our chain. As with any mechanical device, it’s subject to wear, and a worn chain leads to other issues that can cause our bike not to function as it should.

A new chain has rollers that are half an inch apart. Cassettes and chainrings are designed to match with teeth spaced at that same half-inch. As the chain wears the intra-roller distance grows and the result is a chain and cog that don’t mesh well anymore. This can lead to the chain skipping over the teeth of the cog under load or poor shifting. The best way to combat these problems is to make sure the chain is replaced before it’s excessively worn.

Chain Wear Indicator - 1644/2

Unior makes two tools for measuring the wear on a bike chain: the 1643/4 and the 1644/2. Both give a measurement of how worn the chain is as a percentage, and most manufacturers recommend replacing a chain at a 0.6% increase in length.

Unior 1647/2ABI-US Chain Tool

When it comes time to replace that worn chain we also have a selection of tools available to remove the old chain and install a new one. If your chain has a master link you can open it with the 1720/2DP Master Link Removal Pliers. To remove a chain without a master link, and to size and install a new chain, look to our 1647/2ABI and 1647HOBBY/4P chain tools.