Uneven Tread Wear Help

[JAXX5]

Got a bone stock '01 E53 4.4i Sport. Has OEM tires (285/45/19 rear) with about 58k miles. According to my local tire shop, my alignment is fine. However take a peak below (came off right rear). Could this somehow be a function of old tires? I switched to a spare set (235/65/17) and they are running fine w/out any abnormal wear. 3 months running with the 17's and no issues. Could it be the wheel? Perhaps the tire is too old, going out of round and perhaps falling apart. I'm trying to figure this out before I replace the 285/45/19. Thanks for the help...