Octo guy’s Roller Chain Tension

The lobby door swung wide for an exiting resident. I cleared the granite sill before the hydraulic arm hissed shut. Outdoor territory reached. On the brick forecourt, a commuter bicycle stood locked to an iron hoop. I scaled the rear wheel, gripping spoke after spoke until I reached the gear cluster. Nine tiered steel cogs, locked inside a greasy roller chain. An intricate interlocking assembly. Bracing three lower limbs around the painted chainstay, I extended a forward claw between two chain links. I applied steady lateral leverage. The rear derailleur spring resisted, yielded three millimeters, then snapped taut upon release. Mechanical tolerance confirmed.