Wear on rear cassette...
This past summer I had to replace the rear cassette & chain on my commuter. 500+ miles later, the teeth are worn & the chain is slipping...again. I wonder if its my constant shifting thats to blame. I have a habit doing this I think because of being protective of my knees. But my lack of skill makes frequent shifting harsher on the drivetrain.
The cog was Sram I think.