Chain Maintenance
Chain anatomy: To make a chain, we start with a skinny link, containing a pin inside a bushing held between two "inner side plates." Around the bushing, a roller turns freely as the chain contacts the teeth in your cogs. "Outer side plates" -- the fat links -- connect the two sets of inner side plates together, held in place by the pin.
The moving parts of a chain wear out with time. Dirt and sand in the chain act like sandpaper to wear the chain down. As the parts lose close contact, the chain stretches. When the chain no longer fits correctly into the notches on your chainrings and rear cogs, it begins wearing them down. Plan to replace your chain yearly. It's cheaper than new chainrings!
When cleaning the chain, also clean dirt and debris from the rear derailleur pulleys, rear cogs, and chainrings with a brush. Let the chain dry, then lube. Your choice of lube depends on your riding habits, time of year, and choice of trails:
Thin oil (center) must be refreshed often, but it picks up less dirt than heavier oils or grease. It provides rust protection, but is more prone to gumming than chain wax.
At the bottom is a degreaser, used to clean oil from the chain before reapplying lube. "Chain suck" is a dreaded condition where the chain hangs onto the bottom of the small or middle chainring as you pedal. It wraps up around the ring until it hits the incoming chain at the top of the chainring, then it locks everything up, bringing you to an abrupt stop. Keeping the chain clean and well-lubed helps avoid this problem. If it can't be traced to dirt, the problem may be worn teeth on the chainring, or a stiff chain.
Depending on the amount of mud and dirt your chain encounters, your chain should be replaced every 500-1000 miles. A chain that has lengthened or has side-to-side looseness must be replaced.
Make sure the chain is tight. Measure a length of chain containing 12 outer side plates. From the first pin of plate #1 to the first pin of plate #12 should measure exactly 12 inches. (Or, you can simply stretch a brand-new chain alongside the old chain to check how the lengths compare.)
If the chain fails either of these tests, it should be replaced.
A chain repair tool is included on many self-contained bike tool sets.
See the wire? This is a home-made chain-clip, made from a hanger. It holds the ends of the chain together while you work on it.