I squeezed another rock into a car tonight. Ping! Two in one week? I had time and took it, toodling along a longer route. The last three rides have been this way. While most cyclists are breaking the law running red lights, I was rock hounding where I'm not supposed to instead. Got a leak in the process, made it home before needing air. I gradually gather enough rocks to make tree surrounds although a wall's worth would take a decade.