Bike pedals experience wear and tear and sometimes replacements are needed. Luckily, installing or removing pedals is easy if you have a pedal wrench and know that the left pedal is a left-hand thread. Follow these few steps to replace your bicycle parts.
Get a pedal wrench. Most bikes these days require a 15-millimeter pedal wrench. Pedal wrenches work best because they are narrow and can easily fit between the pedal and the crank arm.
Understand that the right pedal is right-hand thread, but the left pedal is LEFT-HAND (reverse) thread - thus, when you go to loosen the left pedal, pretend that you are tightening it.
Apply enough pressure to loosen the pedal. Once loose, you can remove the pedal easily be turning the crank forward while keeping the wrench on the pedal (though this may be difficult if you don't have a bike stand to allow the rear wheel to turn freely).
Screw in the new pedals with your fingers to make sure you don't cross-thread the pedal and strip the threads on the aluminum crank arm. Tighten the pedals securely using the pedal wrench.
Always shift the chain onto the big ring before tightening or loosening pedals. This will prevent you from cutting yourself on the sharp chain-ring teeth if you slip. Some clipless pedals have no wrench flats and will require a 6-millimeter Allen wrench. Some older pedals will require a 9/16-inch wrench. Before installing new pedals, be sure to grease the threads.