Each time a car passes over a gravel-strewn road surface, a few tiny rocks settle into the tire treads.
These particles, smaller than a pea, wedge into the rubber grooves that channel water and provide traction.
Day after day, with trips to the store or errands around town, additional rocks join those already embedded.
The treads gather them steadily, drive by drive, without any notice.
Across many weeks of routine driving, the grooves now contain dozens of these small stones.
One rock adds to another, filling spaces incrementally within the tread patterns.
This collection of tiny rocks sits quietly in the treads, built up through repetition, remaining part of the tire's everyday structure.