Removing the Pedals
Take your bike into a well lit area and look at the pedals. The pedals will be one of two types. The most common is removed and installed with a 15-millmeter pedal wrench or 15-millimeter open-ended wrench. On older bikes, this may require a 9/16-inch wrench instead of the 15 millimeter. These pedals have two flat areas on the shaft of the pedal between the pedal platform and the crank arm. The second type of pedal will use a 6- or 8-millimeter Allen wrench to install and remove. To see if the pedals require an Allen wrench, spin the crank arm until you can see the inside of the crank arm opposite of the crank arm you are turning. If an Allen wrench is needed, you will see a slot for it on the inside of the crank arm where the pedal meets the arm.
Put the bike on your bike stand. If there is no bike stand available, place a towel on the floor and flip the bike upside down, putting the handlebars on the towel. Be sure to remove any bike computers you may have on the handlebars. Then spin the cranks and change the gears until the bike chain is on the largest ring at the crank. This will help protect your knuckles if you slip and hit the crank. Take your penetrating oil or WD-40, and spray a little where the pedals meet the crank arms. Let the bike sit for five minutes.
Start with the right pedal. Put your gloves on. Take the right crank and position it parallel to the ground. Take the 15-millimeter pedal wrench and slide it between the pedal and the crank arm. Try to position it so that it is level with the crank arm. If you don't have a pedal wrench, a 15-millimeter open-ended wrench will work, although it may be difficult to fit it between the pedal and the crank arm. Once the wrench is in place, firmly grasp the wrench with one hand while the other hand holds the opposite crank arm, and pull the wrench counter-clockwise. You may need to "tap" the wrench with a hammer to loosen the pedal. Once the pedal is loose, it should spin off easily.
Be careful not to slip and graze your knuckles across the chain ring.
Move to the left pedal. The left pedal is reverse-threaded. This means that to loosen it, you need to turn it clockwise. Remove the pedal using the same method as the right pedal, remembering to turn it clockwise to loosen.
Prepare the Bike for the New Pedals
Use a clean cloth to wipe the threads on the crank arms and to remove any loose dirt or dust.
Take your pedals out and inspect them. Some pedals are made specifically for the right or left side.. Read the documentation that came with your pedals to see if they have a left and right. If there is no documentation, check the pedals to see if they are marked with "L" or "R."
Put the bike grease on the threads of the pedals. Gently insert the pedals in the crank arms, and gently hand-tighten the pedals. Remember that the left pedal arm is reverse-threaded, so to tighten it, you will need to turn it counter-clockwise. (Remember that you loosened it in Section 1 by turning is clockwise.)
Turn the pedals as tightly as you can with your hand, then get the wrench. Use the wrench to finish tightening them. Do not over-tighten the pedals. Just tighten until you cannot continue without straining. If you have to strain to tighten them, you are using too much force.
Replacing pedals using an Allen Wrench
Follow the same steps to remove and replace your pedals with an Allen Wrench. Remember that the head to insert the Allen Wrench into is on the inside of the crank arm. Because the Allen Wrench is smaller than the pedal wrench and is thinner it will be more difficult to remove "frozen" pedals.