Derailleur Tension

A steel road bicycle leaned against the entryway wall. I scaled the rubber pedal to reach the rear drivetrain. A link hung slack beneath the rear derailleur. I analyzed the assembly; accumulated grit had pinned the lower jockey wheel forward, slackening the chain loop. Bracing my foot against the crank arm, I applied steady backward pressure against the tension cage with two blue fingers. The internal return spring resisted, then snapped cleanly into position. The chain pulled taut across the nine-speed cassette with a sharp metallic clatter. I tapped the pedal forward once. The freewheel engaged without drag. Alignment restored.