How to Easily Replace the Rear Derailleur on Your Mountain Bike
Replacing a rear derailleur on a mountain bike involves removing the old derailleur by unscrewing the chain, removing the derailleur hanger screw, and sliding the derailleur off the hanger. Then, replace the new derailleur by attaching it to the hanger, tightening the screw, and threading the chain through the derailleur. Finally, adjust the derailleur to ensure proper shifting.