In addition to being a serious irritant during your workout, creaking bicycle pedals can indicate a mechanical problem that could cost you money or cause injury if not fixed promptly. Depending on the actual source of the noise, ignoring a creaking pedal could lead to expensive damage to your bicycle--or serious injury if a part breaks while you are riding. Finding the source of the creaking can be tricky, but there are several things you can do to identify and fix the problem.
How to Fix Creaking Bike Pedals
Wash your bike with water and a mild soap, being careful not to spray high-pressure streams of water at any bearings. Simple accumulations of dirt can cause creaking pedals, so check for that before trying anything more involved. Always dry your bicycle thoroughly.
Tighten the pedals with a pedal wrench. Available at specialty bike shops, a pedal wrench is similar to a standard wrench, but it is much thinner so it can fit between the crank arm and the inner end of the pedal. If the pedals are loose, the excess movement could be the source of the noise. Keep in mind that the left-hand pedal will tighten by turning counterclockwise, opposite the direction you would turn to tighten most screws.
Examine the body of the pedals to make sure there are no loose screws. If you have traditional platform pedals, the pedal cage probably is attached to the pedal body with four Phillips-head screws. If you toe cages on your pedals, check the mounting screws. If you use clipless pedals, check the tightness of the screws on the retention plates and the hex bolts that hold the cleats onto your shoes. Loose screws in any of these areas can cause creaking. Worn-out cleats that allow too much movement also might cause the problem.
Consider that the problem might not be the pedals at all, but rather a related or nearby component. A loose crank arm is a common culprit. Check the large hex bolt that holds each arm in place for tightness, and check the hex bolts that fasten the chain rings to the crank arm. Look closely at the front derailleur to ensure that it is not rubbing the chain. Make sure the chain is properly lubricated, as a lack of lubricant is another common source of drive-train noise.