Cranksets

Solution: Learn to pedal faster (about 90 rpm is a good goal), which will put less pressure on the chainring and flex it less. Check for loose chainring bolts. Get the chainring straightened if it's bent.

Problem: There's a trace of play in the sealed bottom bracket.

Solution: Tighten the retaining cup/ring; it may have slightly loosened in the frame.

Problem: There's a creaking sound when you pedal.

Solution: Tighten the crankarm bolts. If the arm still creaks, remove it, apply a trace of grease to the axle, and reinstall the arm.

Problem: You removed the chainrings to clean the crankset and now the front derailleur doesn't shift right.

Solution: You may have installed a chainring upside down. Remove the rings and put them on correctly. Usually, the crankarm bolts fit in indentations on the chainrings. Sight from above, too, to make sure that there's even spacing between the rings.

Problem: You're trying to remove the chainring bolt but it just spins.

Solution: Hold the back half of the chainring bolt with a wide flat-head screwdriver or get a chainring bolt wrench.

Problem: After you overhaul the bottom bracket, the adjustment is either tight or too loose.

Solution: The bearing retainer(s) are installed upside down. Remove and reassemble correctly.

Problem: You bent the bearing retainer when you took the balls out to clean them.

Solution: Try to straighten it, or replace it. If that's not possible, toss the retainers and install loose ball bearings in the bottom bracket.

Problem: There's a knocking sound when you pedal.

Solution: If you have a nonsealed bottom bracket, this sound usually comes from a loose fixed cup (the right-side one). Tighten it securely by turning it counterclockwise.

Problem: The fixed cup on a nonsealed bottom bracket continually loosens.

Solution: Back it out (on modern bikes it's usually turned clockwise), clean the threads, apply thread adhesive, and reinstall tightly.

Problem: You stripped the crankarm threads and now you can't remove the crankarm.

Solution: Just ride the bike around the block a few times. The crankarm will loosen and you'll be able to take it off.

Problem: You crashed into a rock and bent the chainring.

Solution: On the trail, try pounding it straight with a rock. At home, use an adjustable wrench (make the jaws just wide enough to grab the ring) to pry the ring back into place. Or, if it's really bent up, replace it.

Problem: You broke a tooth off the chainring.

Solution: Don't worry about it. It should still work okay. If it's causing the chain to run rough, file down any protruding pieces.