Tech Tips from The Bike Barn: The Chain
Too much oil on the chain is a problem we see far more often than too little oil. Excess oil allows dirt to adhere to your chain, causing excessive wear on both the chain and the chain ring. Excess oil can also soil your bike and your clothing. Lube your chain only when it "talks" too you or after riding in the rain.
One thing all bicyclists should guard against is chain stretch. In 2-4 thousand miles, less if you ride hard, the chain will stretch just enough so it no longer matches the sprockets precisely. To check your own chain, measure 12 inches from the center of a link pin. On a new chain, 12 inches will end up exactly at the center of another pin. If your pin is beyond that, you have chain stretch. If you continue to bicycle with a stretched chain, it can ruin your chainrings in front and your freewheel or cassette in back.