This is an odd mystery, and odd mysteries often have interesting answers. I'm very curious about the cause of the uneven wear.
Is it possible that the tire is not evenly seated on the rim? Perhaps the tire looks even when there is no weight on the bike, but with weight, the left side settles lower so that the actual contact patch with the road is to the left of the center-line of the tread.
I doubt that the camber of the road would cause that wearing. The camber on most roads is so slight that the offset (from the tread center-line) of the wear would be not noticeable.
Do you ride in left-turning circles a lot?
- Dave