Dima's recent trip report jogged my memory of an unsolved mystery I encountered on my way up the north ridge of Mt Williamson: How did this get here?
This tire is located on the broad summit of peak 6621, one of the many bumps on the ridge.
It's been quite a few years since I visited the plane wreck near the top of Pleasant View Ridge, but if I remember correctly, the plane seemed to have been going from the north side of the ridges towards the southeast. Could it be possible that this piece of debris made the journey from one rim of Holcolmb Canyon to the other? If not, I can't really think of why anybody would haul a tire up to the top of peak 6621.