brake rotors dont have threads.just tap the rears with a 14mm tap and get the right size bolts.rotors can easly be drilled to 14mm some are 14mm and you can even tap through the rotor as a guide to the newlly drilled bore as a guide,to make sure youre tap is straight.stay away from helicoils as much as i can.just for smaller less demaNDING BOLTS.