Haven't seen this before and was wondering if it was unusual. I just replaced my rear tire with the exact same Metzler M880 that I had before. When I mounted it, I was sure to clean the rim where the tire bead makes contact with the rim. That area had a little bit of oxidation but nothing I would call excessive. I used tire mounting rubber lube when I installed the new tire. The new tire I received had a current date code and the look and smell was indeed fresh. My wheels are non-laced. Mounted it and thought everything was good to go but I am now loosing air pressure at the rate of 1 PSI per day,,,easily 10 pounds in 2 weeks. I used special bubble leak detector and found several places along the rim bead where I am now loosing air. One side has about (5) 1/4" areas and the other side has maybe 3 areas. Like I said, the rim didn't look that bad but I did use a 3M green scrub pad to remove the oxidation. It was smooth when I was finish. Don't know if it is true but I read that these wheels have clear coat on the bead area and if you remove it, you can have leaks. I have been mounting tires all my life and have never seen a rim go from being air tight to leaking air like a screen door just from cleaning it with green pad. What went wrong? Should I re-clear coat the bead area? Everything seemed perfect,,, now I have to redo it all.