X3 2004 Mix Tires

[msalam]

i wana ask if there is any setting that should be made when switching from same size tires to mix tires? is there any thing related to programability...why when i put same size tires i dont get any problem and when i put mix tires i start getting problems (although the plaque on my door says that i can put mix tires)

any help is realy appreciated cause this problem is unsolvable by the service department of BMW here!