Without a drivetrain, your mountain bike won’t be going anywhere! If it becomes damaged by time, weathering or an accident, you’ll want to replace the damaged parts to prevent other elements breaking and to ensure your MTB stays usable. Decathlon has a full range of mountain bike drivetrain parts - high quality at affordable prices.
Be sure to look after your drivetrain by cleaning it after rides - particularly wet and muddy ones. Grit, dirt and water can damage the drivetrain in a variety of ways and shorten its lifespan so keeping it clean will mean you’ll rarely need to replace any parts.