It has nothing to do with the load o’ tools in the left underseat bag on my Tour Easy. It has everything to do with the fact that we ride on the shoulder of crowned roads.
Here’s a cross-section of one defunct Schwalbe Marathon rear tire with the tread obviously thicker on the left side, which would be the right side of the mounted tire:
Maybe I should change the tires more often?
The Smell of Molten Projects in the Morning 