285/70x17 = 33/12.5x17
Quite true, tires vary a lot. My cousin showed up at our remote camp with his "new" (to him) 2007 FJ. He had to replace the tires right after getting it as the stockers were thin. He got some Definity Dakota AT's at Pep Boys in stock size 265/70-17.for all intents & purposes a 285 would be equal to 11.5"s wide as opposed to 12.5. a 315 wide tire is closer to 12.5"s. As stated it varies quite a bit based on brand.