what would be the first thing to break? on 2006 Mazda MAZDASPEED6

AWD--front and back tires different in size. drove for 6 months until the smaller tires on the back were ripped to shreds along with a grindy, knocking noise coming from all the wheel areas. after putting the same size tires on, just a knocking noise by the wheels and big loss of power

Asked by for the 2006 Mazda MAZDASPEED6
an awd vehicle has to have 4 tires the same size to spin evenly. by changing the tire size front to rear, you are also changing gear ratios, causing the drivetrain to bind and grind. take it to a local transmission shop for further inspection before more damage is done.