Fix It Or Replace It?

1. Chainring Teeth

We’ve seen teeth bent from rough handling, crashes and sloppy shifts (almost always on the outer ring). You’ll know you’ve bent them: The chain will snag or derail as you pedal. Sometimes you can bend the teeth back into place (especially if you have a small adjustable spanner) long enough to get home, but aluminum teeth frequently snap. Missing teeth—torn off in a crash, usually—are more insidious because you can ride a long time without being able to pinpoint the cause of your lousy shifting. (The chain usually deserves most of the blame.) For either malady, replace the ring. If the teeth look fatally worn but intact, double-check the diagnosis with your bike shop; the teeth of modern chainrings and cassettes are so sculpted to enhance shifting that to an unpracticed eye they can appear misshapen even when new.