Bicycle Chain Slippage Due to Drivetrain Wear

This is the most common cause of slippage and is confirmed by inspecting components for physical degradation. Use a chain checker tool to measure elongation; replace the chain if it reaches 0.5% wear (11-12 speed) or 0.75% wear (9-10 speed). Alternatively, use a 12-inch ruler where the 24th rivet must align with the 12-inch mark; if it is more than 1/16th of an inch past, it is worn. Additionally, inspect cassette and chainring teeth for a 'shark-fin' or hooked appearance, which confirms the need for replacement due to gear-mesh incompatibility.