A rusty chain might look like doom for your bicycle. Failing to clean and re-lube your chain regularly can cause rust to form, which causes friction between the teeth on your gears and the chain. This grinds and wears the chainring and cassette until they need to be replaced. You can prevent most of this abrasion simply by cleaning the rust from your chain and keeping it well maintained. Cleaning and servicing the drivetrain of your bicycle is one of the most important types of regular maintenance you can do for your bike, and learning to do it yourself will save you money on bike shop visits.
Removing the Chain
Remove the chain from the drivetrain. Most modern chains feature a "quick link," which can be recognized by the slight indentations on either side of the pin. These links, when pushed in opposite directions, detach from one another and allow removal of the chain. In the absence of a quick link, use a chain tool to force the center pin out from between two links. Save this pin for reattachment later.
Checking for Wear
Before cleaning your chain, it's a good idea to determine if the chain is still safe to use. You can observe the pins in your chain for signs of abrasion. As a chain wears, it undergoes what is commonly referred to as "stretch," but that stretch is actually the metal of the pins being worn away by abrasion. If you can clearly see ruts in one side of the chain pins or if the chain no longer nests perfectly with the cassette due to wear, it may be time to replace your chain. Measure the distance between 12 chain links. If the chain doesn't fall directly on an inch-mark, it has abraded and should likely be replaced.
Removing the Rust
Place the chain in a bottle of citrus de-greaser. A bottle with a wide mouth over 2 inches is safest so the chain doesn't become lodged. Shake the chain vigorously in the citrus de-greaser for an hour or so to dislodge rust and debris. If more buildup remains on the chain, allow the de-greaser to soak for longer, then shake again. You can take the chain out of the bottle using a spoke or length of wire. Then, rinse it thoroughly with water. Don't attempt to lubricate the chain until the chain has completely dried.
Reattaching the Chain
Reattach the chain using the quick link or the chain tool and carefully lubricate it. Excess lubricant will attract dirt, so use it sparingly. Place a single drop on each individual bump in the chain where two links connect around a pin, and allow the lubricant to work its way between the links and into the bushing. After one drop has been applied to each link, run the entire chain through the drivetrain while holding it with a cloth to sweep off the excess oil. Clean any debris, chain lubricant and road grime off the cassette and chainring as well. Be sure to work between the gears on multigeared bicycles to ensure nothing will end up on the chain after it has been cleaned. When all the rust has been removed and the chain is lubricated, you're ready to ride.
Max Roman Dilthey is a science, health and culture writer currently pursuing a master's of sustainability science. Based in Massachusetts, he blogs about cycling at MaxTheCyclist.com.