Drivetrain Analysis

A stationary bicycle rested against the brick threshold of the alley, its lower mechanics within direct reach. I approached the rear wheel hub to inspect the exposed drivetrain. Thick black lubricant and ambient dust coated the articulated links of the chain. Extending my right hand, I applied deliberate upward pressure against the lowest span between the sprockets. The linkage yielded three millimeters before arresting against its tension spring, leaving a faint dark residue across my metal fingertip. The cog teeth exhibited noticeable micro-abrasions, yet the systemic alignment held firm. Satisfied with the tolerance assessment, I withdrew my hand.