I was thinking recently (be afraid.)... how does the chain get dirty? Let's just assume I mean a commuter/road bike in for this question. Is it mostly the water/road grime coming off of the rear tire splashing down on top of the chain? Or is it mostly the water getting splashed up from the front tire hitting the chain on the chainrings?

The "chain tube" thread got me thinking. "If I were to purchase an 8 inch section of chain tube, would it be more effective to place it on the top part of the chain or the bottom part? (Assuming I had a single speed.) The next question was "are traditional (old style) chain guards effective in keeping the chain clean?"

My last question was "I wonder if I can find a slow motion video of a bike riding across the camera's view in slow motion so I could see where most of the water was hitting. Even better if I could see it with and without fenders." Anybody know of any videos like that?