Original size for 15" W126 is 205/65. I use 225/60-15 and they look great on the original 15 x 7 in wheels. 205's look too narrow for such a big car. Anyway, the stated size is not all. Contact patch width of different tires with the same size(diameter) varies. It would be a good idea to comparison shop before you buy. Some people like the rounded edge look(where the tire meets the road) and others like the square edge look.