I think what he is referring to Larry is that the pads don't contact (and therefore do not wear) the outermost edge of the rotor. As the rest of the rotor surface wears down, a noticeable lip is left behind on the outer edge, which you can use to visually track rotor wear.
2007 E550 4Matic - 61,000 Km - Iridium Silver, black leather, Sport package, Premium 2 package
2007 GL450 4Matic - 62,000 Km - Obsidian Black Metallic, black leather, all options
1998 E430 - sold
1989 300E - 333,000 Km - sold
1977 280E - sold
1971 250 - retired
"And a frign hat. They gave me a hat at the annual benefits meeting. I said. how does this benefit me. I dont have anything from the company.. So they gave me a hat." - TheDon