The chain is one of the most critical components on your bicycle. It is responsible for transferring the power generated by your pedaling feet to the rear wheel, and from there to the ground to give you your forward momentum. Without a chain, you ain't goin nowhere -- unless it is downhill.
The earliest bicycles didn't have chains. The pedals connected directly to the wheels, so one turn of the pedals would turn the wheel one revolution. Though simple, this setup required massive drive wheels (we've all seen pictures of the old Penny-farthing style cycles with a huge front wheel) and only had one gear, making hills a problem. Luckily, the development of the chain and the geared bicycle in the 1880's made riding much safer and more efficient.
Modern bicycle chains generally are usually constructed of plain steel, although some lightweight -- and expensive -- titanium models can be found. Chains are designed in a loop that wraps around your crankset (which is the forward set of sprockets - also called chainrings) and the rear sprocket or sprockets (often called a cassette or cogset).
Let's dive into some of the basic information about chains.
Chains are often the first place you will see rust on a bike. After sitting in the garage for a decade or riding out in the rain for a week, a bike chain will often have patches of rust. While this isn’t normally dangerous, rust on the chain can increase the friction and make pedaling your bike much harder.
The easiest way to keep your chain rust-free is to keep your bicycle dry and clean whenever possible. Specially designed chain-cleaning tools can be used to clean off the grime, and wiping down the chain with a rag leaves a dry surface. After this, apply a simple bike lubricant to the chain links to repel water and fend off rust.
People who are bike touring, commuting in the wintertime, mountain biking, or otherwise put a lot of grime and water on their chains can purchase nickel-plated chains that, while slightly more expensive, require less lubrication and rust less easily.
Wear and Tear
The chain takes a great deal of abuse. Every bit of power you put through your legs is transferred through the links of your chain, and after an extended period of time, can result in "chain stretch."
This slight elongation of the chain isn't actually caused by the metal links of the chain stretching out. Rather, chain stretch occurs because the pins that hold the links of your chain together are held in small holes, and these holes deform very slightly over time.
The new sizing of the chain links causes problems, because your chain no longer matches the spacing on your derailleur and your sprockets. This causes more wear and tear on the more expensive components and can lead to your chain slipping when you change gears or pedal powerfully.
Does this sound like what is happening to you? Time to replace your chain! It is easy and only takes a few minutes and a basic set of tools. (Find out how in our helpful chain removal/installation tutorial.)
Sizing a Chain
Modern chains all use the same pitch, or length between links: 1/2-inch. However, chains are designed in different widths. In general, narrower chains are designed for use on bicycles with more gears, to allow for adequate clearance between the chain and the neighboring cogs.
Generally, while shopping for a chain, one can simply count the number of rear sprockets on their bicycle, and then find a chain that supports that number. If you have 8 gears in your rear cogset, chains marked “8-speed” are the models you are looking for. If in doubt, ask for help from an experienced bicycle technician or salesperson.
The length of a chain can be customized based on your bicycle. A basic chain tool, used to remove or install a chain, can also be used to remove excess links and shorten a new chain, which always comes in a more than sufficient length -- as long as it matches your cogset.
Buying and installing a chain is usually a quick and straightforward experience. Just remember to follow our maintenance recommendations, and you will be pedaling happy for many years before you have to replace your chain again.